Objective-C

https://developer.apple.com/library/archive/documentation/Cocoa/Conceptual/ProgrammingWithObjectiveC/Introduction/Introduction.html

String casting

1 2	int num = 1; NSString *str = [NSString stringWithFormat:@"This is string type: %d", num];

will output

1	This is string type: 1

Reference:

Casting an int to an NSString *

Dump object in console

1	NSLog(@"%@", obj);

Reference:

How to dump data stored in objective-c object (NSArray or NSDictionary)

Type casting

Cast bar to NSWhatEver object into foo variable

1	NSWhatEver foo = (NSWhatEver )bar;

Reference:

Casting Objects in Cocoa touch

Accessing a `deep` element in JSON

/*
{
    lvl_1_0 =     {
        lvl_2_0 =         {
            lvl_3_0 = "I'm Foo";
            lvl_3_1 = "I'm Bar";
        };
        lvl_2_1 = 123;
    };
    lvl_1_1 =     (
    );
}
*/

NSString *foo = [[[json valueForKey:@"lvl_1_0"] valueForKey:@"lvl_2_0" ] valueForKey:@"lvl_3_0"];

Clear all cookies

NSString baseUrlString = @"http://yourdomain.com/";
NSArray *cookies = [[NSHTTPCookieStorage sharedHTTPCookieStorage] cookiesForURL: [NSURL URLWithString:baseUrlString]];
for (NSHTTPCookie *cookie in cookies) {
    [[NSHTTPCookieStorage sharedHTTPCookieStorage] deleteCookie:cookie];
}

Reference:

How to manage sessions with AFNetworking?

Clear all NSUserDefaults

NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults];
NSDictionary *dict = [defaults dictionaryRepresentation];
for (id key in dict) {
    [defaults removeObjectForKey:key];
}
[defaults synchronize];

Reference:

Delete all keys from a NSUserDefaults dictionary iPhone

Define global constant

Create 2 files:

1 2	$ touch Constants.h $ touch Constants.m

Add the 2 files to project, right-click the project -> Add Files to “project”…
alt text

Edit the files:

Constants.h

1 2	FOUNDATION_EXPORT NSString const FOO; FOUNDATION_EXPORT NSString const BAR;

Constants.m

1 2	NSString const FOO = @"I'm Foo"; NSString const BAR = @"I'm Bar";

Then import to those files that you want to use these constants

1	import "Constants.h"

Reference:

Constants in Objective C

Add objects into NSMutableArray

NSMutableArray *arrayObj = [[NSMutableArray alloc] init];
for (int i = 0; i < 10; i++) {
    [arrayObj addObject:[NSString stringWithFormat:@"Row %d", i]];
}

Reference:

NSArray adding elements

Add objects into NSMutableDictionary

NSMutableDictionary *arrayObj = [[NSMutableDictionary alloc] init];
for (int i = 0; i < 10; i++) {
    [arrayObj setObject:[NSString stringWithFormat:@"Row %d", i] forKey:[NSString stringWithFormat:@"key_%d", i]];
}

Reference:

How to addObject of NSMutableDictionary to NSMutableArray in a loop

set border to image

#import <QuartzCore/QuartzCore.h>

UIImageView *imageView = [[UIImageView alloc] init];
[imageView.layer setBorderColor:[[UIColor blackColor] CGColor]];
[imageView.layer setBorderWidth:2.0];

Reference:

How can i take an UIImage and give it a black border?

NSDate & Unix timestamp

NSDate to timestamp

1	int timestamp = [[NSDate date] timeIntervalSince1970];

timestamp to NSDate

1 2	int timestamp = 1234567890; NSDate *theDate = [NSDate dateWithTimeIntervalSince1970:timestamp];

References:

Consider a situation here, a 2nd layer view is pushed on top of the root view, where root view need a navigation bar and the view just pushed no need.

In root navigation viewController.m

- (void)viewWillAppear:(BOOL)animated
{
    # show navigation bar when the root view is shown
    [self.navigationController setNavigationBarHidden:NO];
}
- (IBAction)toNextView:(id)sender
{
    # push a new view in
    YourViewController *controller = [[YourViewController alloc] init];
    [self.navigationController pushViewController:controller animated:YES];
    # hide the navigation bar
    [self.navigationController setNavigationBarHidden:YES];
}

Reference:

Hide navigation bar in UINavigationViewController’s root view, but show it in others

Property creation

FooViewController.h

@interface FooViewController : UIViewController

@property (strong, nonatomic) NSString *fooStr;
# primitive type no need to specify strong or weak
@property (nonatomic) int fooInt;

@end

FooViewController.m

@implementation FooViewController { }

@synthesize fooStr;
@synthesize fooInt;

...
- (void)viewDidUnload
{
    // Deallocate object reference type
    [self setFooStr:nil];
    [super viewDidUnload];
}
@end
...

This can be apply in such a situation where you want to let the next view to access your property

Dismiss `presentModalViewController`

i.e. Cancel button is clicked, want to dismiss itself

1	[self dismissModalViewControllerAnimated:YES];

Reference:

present and dismiss modal view controller

UILabel setFont

1	[fooLabel setFont:[UIFont fontWithName:@"Arial-BoldMT" size:16]];

Reference:

I want to make UILabel’s text bold

UILabel center text alignment

1	fooLabel.textAlignment = UITextAlignmentCenter;

Reference:

UILabel Align Text to center

Get device model

#import <sys/utsname.h>
...
- (NSString *)model
{
    struct utsname systemInfo;
    uname(&systemInfo);

    return [NSString stringWithCString:systemInfo.machine encoding:NSUTF8StringEncoding];
}

Reference:

ios iphone get device model and make?

Get user location

First, add a framework named CoreLocation.framework

alt text

In FooViewController.h

#import <UIKit/UIKit.h>
#import <CoreLocation/CoreLocation.h>

@interface FooViewController : UIViewController <CLLocationManagerDelegate> {
    CLLocationManager *locationManager;
}

@end

In FooViewController.m

...
- (void)viewDidLoad
{
    ...
    locationManager = [[CLLocationManager alloc] init];
    locationManager.delegate = self;
    locationManager.distanceFilter = kCLDistanceFilterNone;
    locationManager.desiredAccuracy = kCLLocationAccuracyBest;
    [locationManager startUpdatingLocation];
    ...
}

...
- (void)locationManager:(CLLocationManager *)manager didUpdateToLocation:(CLLocation *)newLocation fromLocation:(CLLocation *)oldLocation
{
    NSLog(@"Old location: %f %f", oldLocation.coordinate.latitude, oldLocation.coordinate.longitude);
    NSLog(@"New location: %f %f", newLocation.coordinate.latitude, newLocation.coordinate.longitude);
}
...

Reference:

How can I get current location from user in iOS

Add beep sound

#import <AudioToolBox/AudioToolBox.h>

...
- (void)viewDidLoad
{
    # more sound refer to http://iphonedevwiki.net/index.php/AudioServices
    AudioServicePlaySystemSound(1000);
}
...

Reference:

has Iphone built in beep sound efect

Bind `Return` button to UITextField

In FooViewController.h

1	@interface FooViewController : UIViewController <UITextFieldDelegate>

In FooViewController.m

- (void)viewDidLoad
{
    ...
    UITextField *textField = [[UITextField alloc] initWithFrame:...];
    ...
    textField.delegate = self;
    ...
}

#pragma mark - UITextFieldDelegate
- (BOOL)textFieldShouldReturn:(UITextField *)textField
{
    // Un-focus the text field
    [textField resignFirstResponder];
    return YES;
}

Reference:

How to make return key on iphone make keyboard disappear?

Change keyboard `Return` key to `Go`

1	[textField setReturnKeyType:UIReturnKeyGo];

Reference:

iOS keyboard with “Go” button instead of return

Delegate multiple UITextField

In FooViewController.m

#import "FooViewController.h"

#define TEXTFIELD_FOO 1
#define TEXTFIELD_BAR 2

@interface FooViewController()

@end

@implementation FooViewController
...
- (void)viewDidLoad
{
    ...
    UITextField *fooTextField = [[UITextField alloc] initWithFrame:...];
    ...
    fooTextField.tag = TEXTFIELD_FOO;
    fooTextField.delegate = self;
    ...
    UITextField *barTextField = [[UITextField alloc] initWithFrame:...];
    ...
    barTextField.tag = TEXTFIELD_BAR;
    barTextField.delegate = self;
    ...
}
...
#pragma mark - UITextFieldDelegate
- (BOOL)textFieldShouldReturn:(UITextField *)textField
{
    if (textField.tag == TEXTFIELD_FOO) {
        // do something with Foo
    } else if (textField.tag == TEXTFIELD_BAR) {
        // do something with Bar
    }
    return YES;
}

Reference:

iphone: uitextfield, multiple textfields with the same delegate?

UIScrollView scroll as page

The statement below will enable the paging like what you see in iPhone menu (cannot scroll half page)

1	scrollView.pagingEnabled = YES;

Change the height of UITableViewCell

- (CGFloat)tableView:(UITableView *)theTableView heightForRowAtIndexPath:(NSIndexPath *)indexPath
{
    return 100.00;
}

Reference:

How can I programmatically increase the height of the cells in my UITableView?

Set UITableViewCell background image

- (UITableViewCell *)tableView:(UITableView *)theTableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
    static NSString *cellIdentifier = @"Cell";
    
    UITableViewCell *cell = [theTableView dequeueReusableCellWithIdentifier:cellIdentifier];
    
    if (cell == nil) {
        cell = [[UITableViewCell alloc] initWithStyle:UITableViewCellStyleSubtitle reuseIdentifier:cellIdentifier];
    }

    cell.backgroundView = [[UIView alloc] init];
    cell.contentView.backgroundColor = [UIColor colorWithPatternImage:[UIImage imageNamed:@"imgName"]];
    
    return cell;
}

Set background on UIButton

I was curious that why the background is always there

alt text

Finally I found the problem, is the Type, to create a button with background programmatically

1
2
3

UIButton *button = [UIButton buttonWithType:UIButtonTypeCustom]; // use custom instead of RoundedRect
[button setFrame:CGRectMake(position_x, position_y, width, height)];
[button setBackgroundImage:[UIImage imageNamed:@"SignInRegisterButton"] forState:UIControlStateNormal];

Remove UITableView cell separator

1	tableView.separatorStyle = UITableViewCellSeparatorStyleNone;

Reference:

How do I remove the borders of a UITableView?

Reset UIBarButtonItem background to default

AppDelegate.m

1	[[UIBarButtonItem appearance] setBackgroundImage:nil forState:UIControlStateNormal barMetrics:UIBarMetricsDefault];

Get `Day`, `Month`, `Year` from NSDate

NSDateComponents *dateComponents = [[NSCalendar currentCalendar] components:NSDayCalendarUnit|NSMonthCalendarUnit|NSYearCalendarUnit fromDate:[NSDate date]];
NSNumber *day = [NSNumber numberWithInt:[dateComponents day]];
NSNumber *month = [NSNumber numberWithInt:[dateComponents month]];
NSNumber *year = [NSNumber numberWithInt:[dateComponents year]];

Reference:

How to parse and extract Year, Month, Day etc from time interval on iphone IOS

Create UITableView programmatically

In YourViewController.h

#import <UIKit/UIKit.h>

@interface YourViewController : UIViewController <UITableViewDelegate, UITableViewDataSource>

@end

Tell the compiler to conform to UITableViewDelegate & UITableViewDataSource these 2 protocols

In YourViewController.m

#import "YourViewController.h"

@interface YourViewController ()

@end

@implementation YourViewController {
        UITableView *tableView;
}
...

- (void)viewDidLoad
{
    tableView = [[UITableView alloc] initWithFrame:CGRectMake(self.view.frame.size.width * 0.55f, self.view.frame.size.height * 0.2f, self.view.frame.size.width * 0.4f, self.view.frame.size.height * 0.7f) style:UITableViewStylePlain];

    // set the delegate & dataSource to self, means have to implement in YourViewController
    tableView.delegate = self;
    tableView.dataSource = self;

    [self.view addSubview:tableView];
}

...
#pragma mark - UITableViewDataSource
- (NSInteger)numberOfSectionsInTableView:(UITableView *)theTableView
{
    // the number of section(s) in the table
    return 1;
}

- (NSInteger)tableView:(UITableView *)theTableView numberOfRowsInSection:(NSInteger)section
{
    // the number of row(s) in the table
    return 1;
}

- (UITableViewCell *)tableView:(UITableView *)theTableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
    static NSString *cellIdentifier = @"Cell";
    
    UITableViewCell *cell = [theTableView dequeueReusableCellWithIdentifier:cellIdentifier forIndexPath:indexPath];
    if (cell == nil) {
        cell = [[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:cellIdentifier];
    }
    // do some configuration like populate data to cell
    
    return cell;
}

#pragma mark - UITableViewDelegate
- (void)tableView:(UITableView *)theTableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath
{
    // Action that you want to perform when clicked on table cell
}

Validate phone number via Regex

NSString *phoneNo = @"+6012-3456789";
NSString *regex = @"^(\\+)?\\d+(-)?\\d+";
NSPredicate *stringTest = [NSPredicate predicateWithFormat:@"SELF MATCHES %@", regex];
BOOL isValid = [stringTest evaluateWithObject:phoneNo];

^ Indicate beginning of the text
(\\+)? Is an optional + character at the beginning of the text
\\d+ Indicate one or more integer
(-)? An optional character

This will matches:

+6012-3456789
012-3456789
+60123456789
6012-3456789
60123456789

Validate required text field

Should use

1
2
3

if (textField.text.length == 0) {
    // handle error
}

rather than

1
2
3

if ([textField.text isEqualToString:@""]) {
    // handle error
}

The second 1 won’t work as it’s default value is not an empty string, unless that you set

- (void)viewDidLoad
{
    [super viewDidLoad];
    textField.text = @"";
}

it’s initial value.

Reference:

UITextField Initial Value

Disable sleep

In your AppDelegate.m

...
- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
    [UIApplication sharedApplication].idleTimerDisabled = YES;
}
...

Reference:

How to Disable Sleep, but Enable Screen Dimming

Adding criteria to CoreData

NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init];
    
NSEntityDescription *entity = [NSEntityDescription entityForName:@"TableName" inManagedObjectContext:self.managedObjectContext];
[fetchRequest setEntity:entity];

NSSortDescriptor *sortDescriptor = [NSSortDescriptor sortDescriptorWithKey:@"id" ascending:YES];
[fetchRequest setSortDescriptors:[NSArray arrayWithObject:sortDescriptor]];

/* Add criteria here */
// for integer
[fetchRequest setPredicate:[NSPredicate predicateWithFormat:@"theId == %d", 123]];
// for string
[fetchRequest setPredicate:[NSPredicate predicateWithFormat:@"columnName CONTAINS[cd] %@", @"foo"]];

NSError *error;
NSArray *resultSet = [self.managedObjectContext executeFetchRequest:fetchRequest error:&error];
if (resultSet == nil) {
    FATAL_CORE_DATA_ERROR(error);
}

NSLog(@"Result: %@", resultSet);

Reference:

NSPredicate compare with Integer

Sentence to CamelCase

- (NSString *)camelCaseFromString:(NSString *)str
{
    return [[str capitalizedString] stringByReplacingOccurrencesOfString:@" " withString:@""];
}

Reference:

How to convert text to camel case in Objective-C?

Add touch event to UIImageView

UITapGestureRecognizer *tap = [[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(imageTouched:)];

UIImageView *imageView = [[UIImageView alloc] initWithFrame:CGRectMake(0, 0, 100, 100)];
[imageView addGestureRecognizer:tap];
imageView.userInteractionEnabled = YES;
[self.view addSubview:imageView];

...

- (void)imageTouched:(UITapGestureRecognizer *)sender
{
    NSLog(@"Image tapped");
}

NOTE: imageView.userInteractionEnabled = YES must be set, otherwise it won’t work

NSArray check is object in array

1 2	NSArray *foo = [NSArray arrayWithObjects:obj1, obj2, obj3, nil]; BOOL isObj1InArray = [foo containsObject:obj1];

Reference:

in_array() for objective-c

Set timeout interval

Set the interval to 60 seconds.

1
2
3

// must be NSMutableURLRequest, NSURLRequest doesn't has setTimeoutInterval this method
NSMutableURLRequest *request = [client requestWithMethod:@"GET" path:@"/foo" parameters:nil];
[request setTimeoutInterval:60];

Reference:

How to set a timeout with AFNetworking

Compare CGRect

1
2
3

if (CGRectEqualToRect(someView.frame, anotherView.frame)) {
    NSLog(@"They are equal");
}

Reference:

Comparing two CGRects

Open browser when click on hyperlink in UIWebView

In your FooViewController.h, make sure it conform to WebView’s protocol

#import <UIKit/UIKit.h>

@interface FooViewController : UIViewController <UIWebViewDelegate>

@end

In FooViewController.m, implement the delegate method

#pragma mark - UIWebViewDelegate
- (BOOL)webView:(UIWebView *)webView shouldStartLoadWithRequest:(NSURLRequest *)request navigationType:(UIWebViewNavigationType)navigationType
{
    // if a hyperlink is onclick, open browser
    if (navigationType == UIWebViewNavigationTypeLinkClicked) {
        [[UIApplication sharedApplication] openURL:request.URL];
        return NO;
    }
    return YES;
}

Reference:

Launch Safari from UIWebview

Access property variable in closure

When you see a warning Capturing ‘self’ strongly in this block is likely to lead to a retain cycle, you can’t access via self inside the block.

[self.coverImageView setImageWithURLRequest:[NSURLRequest requestWithURL:[NSURL URLWithString:[json valueForKeyPath:@"response.cover"]]] placeholderImage:nil success:^(NSURLRequest *request, NSHTTPURLResponse *response, UIImage *image) {
            
    self.coverImageView.image = image; // warning will be appeared here
} failure:^(NSURLRequest *request, NSHTTPURLResponse *response, NSError *error) {
}];

The solution is

__weak typeof(self) weakSelf = self;
[self.coverImageView setImageWithURLRequest:[NSURLRequest requestWithURL:[NSURL URLWithString:[json valueForKeyPath:@"response.cover"]]] placeholderImage:nil success:^(NSURLRequest *request, NSHTTPURLResponse *response, UIImage *image) {
            
    weakSelf.coverImageView.image = image;
} failure:^(NSURLRequest *request, NSHTTPURLResponse *response, NSError *error) {
}];

Reference:

capturing self strongly in this block is likely to lead to a retain cycle

Add a Done button to UISearchBar

// add Done button to keyboard
// dummy bar button just to make the Done button to right-hand-side
UIBarButtonItem *dummyBarButton = [[UIBarButtonItem alloc] initWithBarButtonSystemItem:UIBarButtonSystemItemFlexibleSpace target:nil action:nil];
UIBarButtonItem *doneBarButton = [[UIBarButtonItem alloc] initWithBarButtonSystemItem:UIBarButtonSystemItemDone target:self action:@selector(hideKeyboard:)];
[doneBarButton setStyle:UIBarButtonItemStyleDone];
UIToolbar *keyboardToolbar = [[UIToolbar alloc] init];
[keyboardToolbar setBarStyle:UIBarStyleBlackTranslucent];
[keyboardToolbar sizeToFit];
[keyboardToolbar setItems:[NSArray arrayWithObjects:dummyBarButton, doneBarButton, nil]];

self.searchBar = [[UISearchBar alloc] initWithFrame:CGRectMake(0, 0, 320, 44)];
self.searchBar.delegate = self;
self.searchBar.placeholder = @"Search...";
// Access it subview (UITextField) and set the toolbar to it
// Since self.searchBar.inputAccessoryView = keyboardToolbar; will thrown error
for (UIView *subView in self.searchBar.subviews) {
    if ([subView conformsToProtocol:@protocol(UITextInputTraits)]) {
        UITextField *searchBarField = (UITextField *)subView;
        searchBarField.inputAccessoryView = keyboardToolbar;
        break;
    }
}
[self.view addSubview:self.searchBar];

Reference:

Issue with UISearchBar inputAccessoryView

Change UISearchBar Search button to Done


self.searchBar = [[UISearchBar alloc] initWithFrame:CGRectMake(0, 0, 320, 44)];
self.searchBar.delegate = self;
self.searchBar.placeholder = @"Search...";
// Loop through all subviews in UISearchBar
for (UIView *searchBarSubview in [self.searchBar subviews]) {
    // Check if it is UITextField
    if ([searchBarSubview conformsToProtocol:@protocol(UITextInputTraits)]) {
        @try {
            // Change the title "Search" to "Done"
            [(UITextField *)searchBarSubview setReturnKeyType:UIReturnKeyDone];
            // set the style of keyboard
            [(UITextField *)searchBarSubview setKeyboardAppearance:UIKeyboardAppearanceAlert];
            // Enable the "Done" button eventhough no text in search bar
            [(UITextField *)searchBarSubview setEnablesReturnKeyAutomatically:NO];
        }
        @catch (NSException * e) {
            // ignore exception
        }
    }
}
[self.view addSubview:self.searchBar];

Reference:

iphone UISearchBar Done button always enabled

Remove all subviews from UIScrollView

1	[self.scrollView.subviews makeObjectsPerformSelector:@selector(removeFromSuperview)];

Reference:

Remove all the subviews from a UIScrollView?

Calculate visible “radius” from MKMapView

// get the center coordinate
CLLocationCoordinate2D centerCoor = [self.mapView centerCoordinate];
// get top left coordinate
CLLocationCoordinate2D topLeftCoor = [self.mapView convertPoint:CGPointMake(0, 0) toCoordinateFromView:self.mapView];

// init locations based on coordinates
CLLocation *centerLocation = [[CLLocation alloc] initWithLatitude:centerCoor.latitude longitude:centerCoor.longitude];
CLLocation *topLeftLocation = [[CLLocation alloc] initWithLatitude:topLeftCoor.latitude longitude:topLeftCoor.longitude];

// get the distance between 2 locations
CLLocationDistance radius = [centerLocation distanceFromLocation:topLeftLocation];

NSLog(@"Distance %.9f meters", radius);

Reference:

How to get left-top and right-buttom latitude and longitude of map in MapKit

Draw a circle image

This is basically just to draw a UIImage (circle) from code.

- (UIImage *)drawCircleWithColor:(UIColor *)color andSize:(CGSize)size
{
    CGRect rect = CGRectMake(0, 0, size.width, size.height);
    UIGraphicsBeginImageContext(rect.size);
    
    CGContextRef context = UIGraphicsGetCurrentContext();
    CGContextSetLineWidth(context, 4.0);
    CGContextSetStrokeColorWithColor(context, [UIColor whiteColor].CGColor);
    CGContextSetFillColorWithColor(context, color.CGColor);
    
    CGContextBeginPath(context);
    CGContextAddEllipseInRect(context, rect);
    CGContextDrawPath(context, kCGPathFillStroke); // Or kCGPathFill

    UIImage *circle = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
    
    return circle;
}

References:

Create rectangle UIImage programmatically

- (UIImage *)imageWithColor:(UIColor *)color inSize:(CGSize)size withCornerRadius:(CGFloat)radius
{
    CGRect rect = CGRectMake(0, 0, size.width, size.height);
    UIGraphicsBeginImageContext(rect.size);
    CGContextRef context = UIGraphicsGetCurrentContext();
    CGContextSetFillColorWithColor(context, color.CGColor);
    CGContextFillRect(context, rect);
    UIImage *img = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();

    if (radius > 0) {
        UIGraphicsBeginImageContext(size);
        
        // Add a clip before drawing anything, in the shape of an rounded rect
        [[UIBezierPath bezierPathWithRoundedRect:rect cornerRadius:radius] addClip];
        // Draw your image
        [img drawInRect:rect];
        img = UIGraphicsGetImageFromCurrentImageContext();
        UIGraphicsEndImageContext();
    }
    
    return img;
}

References:

Update text on a specific UITableViewCell

For example update, the fifth row in section 0

1
2
3

NSIndexPath *fifthRow = [NSIndexPath indexPathForRow:4 inSection:0];
UITableViewCell *cell = [tableView cellForRowAtIndexPath:fifthRow];
cell.textLabel.text = @"the updated text";

Reference:

UITableViewCell: How do I update textLabel.text at fifth row?

Remove last 2 character in NSMutableString

1 2	NSMutableString *str = [NSMutableString stringWithString:@"Item 1, Item 2, "]; [str deleteCharactersInRange:NSMakeRange([str length] - 2, 2)];

Result will be Item 1, Item 2

Reference: Removing the last character from an NSMutableString

Get all checked UITableViewCell

// options is the dataSource for the tableView
for (int i = 0; i < [options count]; i++) {
    UITableViewCell *cell = [tableView cellForRowAtIndexPath:[NSIndexPath indexPathForRow:i inSection:0]];
    if (cell.accessoryType == UITableViewCellAccessoryCheckmark) {
        // perform action here
    }
}

Reference:

Selecting multiple rows of a UITableView

UIView get index of subview

Some time you might have some views is overlapping, when tapping a button, the 2 views will interchange, so you need to get the view’s index to do comparison.

UIView *superView = [[UIView alloc] init];

UITableView *listView = [[UITableView alloc] initWithFrame:superView.bounds];
[superView addSubview:listView];

UITableView *gridView = [[UITableView alloc] initWithFrame:superView.bounds];
[superView addSubview:gridView];

int listViewIndex = [superView.subviews indexOfObject:listView];
int gridViewIndex = [superView.subviews indexOfObject:gridView];

// action here

Reference:

How to get UIView hierarchy index ??? (i.e. the depth in between the other subviews)

UINavigationBar change back bar button text

Let say there are 2 viewControllers, FirstViewController and SecondViewController

In FirstViewController.m

...
- (void)viewDidLoad
{
    // This must be put in FirstViewController rather than SecondViewController
    self.navigationItem.backBarButtonItem = [[UIBarButtonItem alloc] initWithTitle:@"Your title"
                                                                             style:UIBarButtonItemStyleBordered
                                                                            target:nil
                                                                            action:nil];
}
- (void)navigateToSecondView
{
    SecondViewController *controller = [[SecondViewController alloc] init];
    [self.navigationController pushViewController:controller animated:YES];
}
...

When you navigate to SecondViewController, you will see Your title text appear in back button.

Reference:

UINavigationController “back button” custom text?

tableView:viewForFooterInSection VS tableView.tableFooterView

If you want the footer to keep at the end of table view (it will scroll together with table cell), then use tableView.tableFooterView

UIView *footerView = [[UIView alloc] initWithFrame:...];
[footerView addSubview:someView];

tableView.tableFooterView = footerView;

If you’re using tableView:viewForFooterInSection, then the view will stay at bottom of your visible screen for that particular section.


- (UIView *)tableView:(UITableView *)tableView viewForFooterInSection:(NSInteger)section
{
    UIView *footerView = [[UIView alloc] initWithFrame:...];
    ...
    [footerView addSubview:someView];

    return footerView;
}

Reference:

UITableView Footer, Stop from floating over content

RSA - Convert `.pem` to `.der` format

NSString *startPublicKey = @"-----BEGIN PUBLIC KEY-----";
NSString *endPublicKey = @"-----END PUBLIC KEY-----";

// read .pem from file
NSString* path = [[NSBundle mainBundle] pathForResource:@"public_key"
                                                     ofType:@"pem"];
// get the content
NSString* content = [NSString stringWithContentsOfFile:path
                                                  encoding:NSUTF8StringEncoding
                                                     error:NULL];
// remove the first line & end line
NSString *publicKey;
NSScanner *scanner = [NSScanner scannerWithString:content];
[scanner scanUpToString:startPublicKey intoString:nil];
[scanner scanString:startPublicKey intoString:nil];
[scanner scanUpToString:endPublicKey intoString:&publicKey];

// now this is in .der format
NSData *data = [NSData base64DataFromString:publicKey];

References:

Storing Custom object to NSUserDefaults

Let say you have an object Foo

Foo.h

#import <Foundation/Foundation.h>

// conform to NSCoding
@interface Foo : NSObject <NSCoding>

@property (nonatomic, strong) NSString *name;
@property (nonatomic, strong) NSString *desc;

@end

Foo.m

#import "Foo.h"

@implementation Foo

@synthesize name = _name;
@synthesize desc = _desc;

// implement this 2 methods
- (void)encodeWithCoder:(NSCoder *)aCoder
{
    [aCoder encodeObject:self.name forKey:@"Name"];
    [aCoder encodeObject:self.desc forKey:@"Desc"];
}

- (id)initWithCoder:(NSCoder *)aDecoder
{
    self.name = [aDecoder decodeObjectForKey:@"Name"];
    self.desc = [aDecoder decodeObjectForKey:@"Desc"];
    
    return self;
}

Now you can save your objects to NSUserDefaults

NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults];
NSMutableArray *arr = ... ; // set value
NSData *data = [NSKeyedArchiver archivedDataWithRootObject:arr];
[defaults setObject:data forKey:@"theKeyInUserDefaults"];

and load it from NSUserDefaults

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NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults];
NSData *data = [defaults objectForKey:@"theKeyInUserDefaults"];
NSArray *arr = [NSKeyedUnarchiver unarchiveObjectWithData:data];

Reference:

Why NSUserDefaults failed to save NSMutableDictionary in iPhone SDK?

Compare NSObject

Override the hash & isEqual methods

- (NSUInteger)hash
{
    NSUInteger prime = 31;
    NSUInteger result = 1;
    
    // for object
    result = prime * result + [self.name hash];

    // for primitive type
    result = prime * result + self.amount;

    // for 64bit
    result = prime * result + (int) (self.data64bit ^ (self.data64bit >>> 32));

    // for boolean
    result = prime * result + (self.isCorrect) ? 1231 : 1237;

    return result;
}

- (BOOL)isEqual:(id)object
{
    if (![object isKindOfClass:[self class]]) {
        return NO;
    }
    return [self hash] == [object hash];
}

Reference:

Best practices for overriding isEqual: and hash

Change textLabel color of UITableViewCell in `selected` state

1	cell.textLabel.highlightedTextColor = [UIColor whiteColor];

Reference:

iPhone: How to change font color in UITableViewCell when selected?

Rate Us: Open in AppStore

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NSURL *rateUrl = [NSURL URLWithString:[NSString stringWithFormat:@"itms-apps://itunes.apple.com/WebObjects/MZStore.woa/wa/viewContentsUserReviews?id=%@&onlyLatestVersion=true&pageNumber=0&sortOrdering=1&type=Purple+Software", @"YOUR_APP_ID_HERE"]];

[[UIApplication sharedApplication] openURL:rateUrl];

Reference:

App store link for “rate/review this app”

Add shadow to view without gradient

alt text

To add a shadow to UINavigationBar like image above

// set shadow below
self.navigationController.navigationBar.layer.shadowRadius = 0;
self.navigationController.navigationBar.layer.shadowOffset = CGSizeMake(0, 4);
self.navigationController.navigationBar.layer.shadowOpacity = 1;
self.navigationController.navigationBar.layer.shadowColor = [UIColor colorWithWhite:0.8 alpha:0.8f].CGColor;
self.navigationController.navigationBar.layer.shadowPath = [UIBezierPath bezierPathWithRoundedRect:self.navigationController.navigationBar.bounds cornerRadius:self.navigationController.navigationBar.layer.cornerRadius].CGPath;

Reference:

Shadow in UIView without gradient ?

Resign any first responder

Some time we just want to hide the keyboard when clicked on a button, but we might not know which textField is currently showing keyboard. The line below will just resign any responder.

1	[self.view endEditing:YES];

Reference:

Get the current first responder without using a private API

Loop through NSDictionary

NSDictionary *dict = ...;
for (NSString *key in dict) {
    id value = [dict objectForKey:key];
    // do stuff
}

Reference:

for each loop in objective c for accessing NSMutable dictionary

UINavigationBar in iOS7 overlap the main content view issue

alt text

In order to fix this, just add the line below

1	navigationController.navigationBar.translucent = NO;

Reference:

Status bar and navigation bar appear over my view’s bounds in iOS 7

Draw UIImage from text

- (UIImage *)imageFromText:(NSString *)text
{
    // set the font type and size
    UIFont *font = [UIFont fontWithName:@"Helvetica" size:12];
    CGSize size  = [text sizeWithFont:font];
    
    // check if UIGraphicsBeginImageContextWithOptions is available (iOS is 4.0+)
    if (UIGraphicsBeginImageContextWithOptions != NULL)
        UIGraphicsBeginImageContextWithOptions(size,NO,0.0);
    else
        // iOS is < 4.0
        UIGraphicsBeginImageContext(size);
    
    // optional: add a shadow, to avoid clipping the shadow you should make the context size bigger
    //
    // CGContextRef ctx = UIGraphicsGetCurrentContext();
    // CGContextSetShadowWithColor(ctx, CGSizeMake(1.0, 1.0), 5.0, [[UIColor grayColor] CGColor]);
    
    // set text color
    [[UIColor colorWithWhite:1 alpha:0.55] set];
    
    // draw in context, you can use also drawInRect:withFont:
    [text drawAtPoint:CGPointMake(0.0, 0.0) withFont:font];
    
    // transfer image
    UIImage *image = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
    
    return image;
}

Reference:

How do I use the NSString draw functionality to create a UIImage from text

Change UINavigationBar style

In AppDelegate.m

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
    ...

    // change the font & text color
    [[UINavigationBar appearance] setTitleTextAttributes:[NSDictionary dictionaryWithObjectsAndKeys:
                      [UIFont fontWithName:@"CustomFont-Bold" size:18], UITextAttributeFont,
                      [UIColor whiteColor], UITextAttributeTextColor,
                      // make the text FLAT
                      [UIColor clearColor], UITextAttributeTextShadowColor,
                      nil]];
    ...
}

This is same to UIBarButtonItem

Reference:

Change UINavigationBar font properties?

UINavigationBar bar button image color for iOS7

In iOS7, even you set an image which is white color, it will automatic become blue color. This can change it by tintColor.

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if ([[UIDevice currentDevice].systemVersion floatValue] >= 7) {
    [[UINavigationBar appearance] setTintColor:[UIColor whiteColor]];
}

Change status bar text color for iOS7

On ViewController

Set the UIViewControllerBasedStatusBarAppearance to YES in the plist.
Edit ViewController.m

- (void)viewDidLoad
{
    [super viewDidLoad];

    // ADD THIS LINE
    [self setNeedsStatusBarAppearanceUpdate];
}

// ADD THIS METHOD
- (UIStatusBarStyle)preferredStatusBarStyle { 
    return UIStatusBarStyleLightContent; 
}

OR Update the UINavigationBar color, then it will follow. Put the code below to application:didFinishLaunchingWithOptions:

// only for iOS7
if ([[UIDevice currentDevice].systemVersion floatValue] >= 7) {
    [[UINavigationBar appearance] setBarTintColor:[UIColor yellowColor]];
}

On splash screen

Edit Info.plist

<dict>
    ...
    <key>UIStatusBarStyle</key>
    <string>UIStatusBarStyleLightContent</string>
    ...
</dict>

References:

UIView autoresizingMask to bottom left

If want to achive the result like this in programmatic way

alt text

1 2	// flexible right & flexible top view.autoresizingMask = UIViewAutoresizingFlexibleRightMargin \| UIViewAutoresizingFlexibleTopMargin;

Reference:

UIView autoresizingMask problem

Check location service enabled for this app

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3

if ([CLLocationManager authorizationStatus] == kCLAuthorizationStatusDenied) {
    // location service is not allowed for this app
}

Reference:

How to check if location services are enabled for a particular app prior to iOS 4.2?

A trigger of after view added to subview

A CustomView want to execute some logic once added to other view

ViewController.m

1 2	CustomView *view = [[CustomView alloc] init]; [self.view addSubview:view];

CustomView.m

- (void)didMoveToSuperview
{
    NSLog(@"Just added to other view");
}

Reference:

iPhone/iOS: Will there be called any method if a UIView is added as a subview

Show static map (Google) on UIImageView

UIImageView *imageView = [[UIImageView alloc] initWithFrame:CGRectMake(position_x, position_y, width, height)];

double latitude = 3.4005, longitude = 101.34888;
int zoomLevel = 11;

NSString *staticMapUrlString = [NSString stringWithFormat:@"http://maps.google.com/maps/api/staticmap?markers=color%%3Ared%%7C%f,%f&zoom=%d&size=%dx%d&sensor=true", latitude, longitude, zoomLevel, (int)imageView.bounds.size.width, (int)imageView.bounds.size.height];
NSURL *staticMapUrl = [NSURL URLWithString:staticMapUrlString];

imageView.image = [UIImage imageWithData: [NSData dataWithContentsOfURL:staticMapUrl]];

String encoding in URL

%%3A - is refer to colon (:), the double percent (%%) is to escape the string parameters
%%7C - is refer to the pipe line (|)

References:

Detect `double tap` event on UIImageView

- (void)viewDidLoad
{
    ...
    ImageView *imageView = [[UIImageView alloc] initWithFrame:frame];
    imageView.image = image;
    imageView.userInteractionEnabled = YES; // must enable

    UITapGestureRecognizer *tap = [[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(imageTapped:)];
    [tap setDelaysTouchesBegan:YES];
    tap.numberOfTapsRequired = 2; // double tap
    tap.numberOfTouchesRequired = 1;
    [imageView addGestureRecognizer:tap];
}

- (void)imageTapped:(UITapGestureRecognizer *)sender
{
    NSLog(@"Double tapped");
}

Reference:

Detect Double tap in UIScrollView

Show character by give ASCII code (int) or vice versa

Integer to alphabet

1 2	int asciiCode = 97; NSString *alphabet = [NSString stringWithFormat:@"%c", asciiCode]; // a

Alphabet to integer

1 2	NSString *alphabet = @"a"; int asciiCode = [alphabet characterAtIndex:0]; // 97

Reference:

How to convert ASCII value to a character in Objective-C?

Change UITabBarController tint color

Change the bar color

1	tabBarController.tabBar.barTintColor = [UIColor blackColor];

Change the icon & text color

1	tabBarController.tabBar.tintColor = [UIColor whiteColor];

Change the text color only

// change the selected text color
[[UITabBarItem appearance] setTitleTextAttributes:@{NSFontAttributeName: [UIFont fontWithName:@"Helvetica" size:10.0f],
                                                    NSForegroundColorAttributeName: [UIColor whiteColor]
                                                    } forState:UIControlStateSelected];


// change the unselected text color
[[UITabBarItem appearance] setTitleTextAttributes:@{NSFontAttributeName: [UIFont fontWithName:@"Helvetica" size:10.0f],
                                                    NSForegroundColorAttributeName: [UIColor whiteColor]
                                                    } forState:UIControlStateNormal];

Reference:

How can I change the text and icon colors for tabBarItems in iOS 7?

Fix the status bar some time not showing text on iOS7

Edit Project-Info.plist file, add the content below

1 2	<key>UIViewControllerBasedStatusBarAppearance</key> <false/>

Or open in Property list

alt text

Extract submatch from string using regular expression

Example here shows extract date from NSDate object

The format we want is YYYY-MM-DD

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NSLog(@"date %@", date);
// this will return (for example)
// 2014-01-27 10:17:00 +0000

So we can extract out the part using regex

NSDate *date = ...;

// extract 4 integers followed by a dash followed by 2 integers followed by a dash followed by 2 integers again
NSRegularExpression *regex = [NSRegularExpression regularExpressionWithPattern:@"(\\d{4}-\\d{2}-\\d{2})"
                                                                       options:NSRegularExpressionCaseInsensitive
                                                                         error:&error];
[regex enumerateMatchesInString:date.description options:0 range:NSMakeRange(0, date.description.length) usingBlock:^(NSTextCheckingResult *result, NSMatchingFlags flags, BOOL *stop) {
    // just get the substring by the range
    NSString *dateStr = [sender.date.description substringWithRange:[result rangeAtIndex:0]];
    NSLog(@"Date only: %@", dateStr);
    // this will show
    // Date only: 2014-01-27
}];

Update

For this case, want to extract out the minutes & seconds

NSString *message = @"Your computer will be shutdown in 3 minutes 25 seconds";

// Only match for the minutes & seconds
NSRegularExpression *regex = [NSRegularExpression regularExpressionWithPattern:@"(\\d+) minutes (\\d+) seconds"
                                                                       options:NSRegularExpressionCaseInsensitive
                                                                         error:&error];
[regex enumerateMatchesInString:date.description options:0 range:NSMakeRange(0, date.description.length) usingBlock:^(NSTextCheckingResult *result, NSMatchingFlags flags, BOOL *stop) {

    // `rangeAtIndex` 0 will be "3 minutes 25 seconds, so we don't take
    // `rangeAtIndex` 1 will be "3"
    // `rangeAtIndex` 2 will be "25"
    int minutes = [[message substringWithRange:[result rangeAtIndex:1]] intValue];
    int seconds = [[message substringWithRange:[result rangeAtIndex:2]] intValue];
    NSLog(@"%dm %ds", minutes, seconds); // 3m 25s
}];

It always matches the main match then only followed by submatch

Reference:

Extract parts from regular expression with NSRegularExpression

Resize UIImage


+ (UIImage *)resizeImage:(UIImage *)image withSize:(CGSize)size retainAspectRatio:(BOOL)aspectRatio
{
    CGSize newSize = size;
    if (aspectRatio) {
        // whether is based on width to calculate or height
        BOOL baseOnWidth = size.width > size.height ? YES : NO;
        
        if (baseOnWidth) {
            newSize.height = (size.width / image.size.width) * image.size.height;
        } else {
            newSize.width = (size.height / image.size.height) * image.size.width;
        }
    }
    UIGraphicsBeginImageContextWithOptions(newSize, NO, 0.0);
    [image drawInRect:CGRectMake(0, 0, newSize.width, newSize.height)];
    UIImage *newImage = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
    return newImage;
}

Reference:

The simplest way to resize an UIImage?

`UISegmentedControl` deselect segment

1	[segmentedControl setSelectedSegmentIndex:UISegmentedControlNoSegment];

Reference:

UISegmentedControl deselect (make none of the segments selected)

`UISegmentedControl` change text & border color

Border color

1	segmentedControl.tintColor =[UIColor colorWithRed:50/255.0f green:150/255.0f blue:100/255.0f alpha:1];

Text color

1	[segmentedControl setTitleTextAttributes:@{UITextAttributeTextColor: [UIColor blueColor]} forState:UIControlStateSelected];

Add `UISegmentedControl` to `UIToolbar`

UISegmentedControl *nextPrevSegment = [[UISegmentedControl alloc] initWithItems:@[@"Previous", @"Next"]];
nextPrevSegment.segmentedControlStyle = UISegmentedControlStyleBar;
[nextPrevSegment addTarget:self action:@selector(nextPrevTouched:) forControlEvents:UIControlEventValueChanged];
UIBarButtonItem *segmentedControlButtonItem = [[UIBarButtonItem alloc] initWithCustomView:(UIView *)nextPrevSegment];
UIToolbar *keyboardToolbar = [[UIToolbar alloc] init];
[keyboardToolbar setTintColor:[UIColor whiteColor]];
[keyboardToolbar sizeToFit];
[keyboardToolbar setItems:[NSArray arrayWithObjects:segmentedControlButtonItem, [[UIBarButtonItem alloc] initWithBarButtonSystemItem:UIBarButtonSystemItemFlexibleSpace target:nil action:nil], nil]];

Use custom font in `UIWebView`

NSString *html = @"<p>This is a paragraph<\/p>";
NSString *htmlString = 
    [NSString stringWithFormat:@"<font face='GothamRounded-Bold' size='2'>%@", html];
[webView loadHTMLString:htmlString baseURL:nil];

Reference:

How to change UIWebView default font

Set delay to perform action

double delayInSeconds = 2.0;
dispatch_time_t popTime = dispatch_time(DISPATCH_TIME_NOW, delayInSeconds * NSEC_PER_SEC);
dispatch_after(popTime, dispatch_get_main_queue(), ^(void){
    //code to be executed on the main queue after delay
    NSLog(@"Action here delayed 2 seconds.");
});

Reference:

how to call a method with delay

Remove section border for iOS6

1	cell.backgroundView = [UIView new];

Reference:

Removing cell borders from a section of grouped-style UITableView

UITableView grouped style change background color for iOS6

transparent background

1	tableView.backgroundView = [UIView new];

for color background

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UIView* bview = [[UIView alloc] init];
bview.backgroundColor = [UIColor yellowColor];
[tableView setBackgroundView:bview];

Reference:

Set background color on UITableView in IOS 6 [duplicate]

Make the UINavigationBar transparent

self.navigationController.navigationBar.shadowImage = [UIImage new];
// remove the inner shadow

// for iOS 7, remove the background image
if ([[UIDevice currentDevice].systemVersion floatValue] >= 7) {
    [self.navigationController.navigationBar setBackgroundImage:[UIImage new] forBarMetrics:UIBarMetricsDefault];
    self.navigationController.navigationBar.shadowImage = [UIImage new];
    self.navigationController.navigationBar.translucent = YES;
    self.navigationController.view.backgroundColor = [UIColor clearColor];
} else { // for iOS 6, set the image filled with color that same as the view's background color
    // see https://github.com/jslim89/js-learning-journey/tree/master/programming/objective-c#create-rectangle-uiimage-programmatically
    [self.navigationController.navigationBar setBackgroundImage:[MyClass imageWithColor:[UIColor yellowColor] inSize:CGSizeMake(320, 44) withCornerRadius:0] forBarMetrics:UIBarMetricsDefault];
}

References:

Set 2 different colors in a view

This can be achieved by using CALayer

CALayer *sublayer = [CALayer layer];
sublayer.backgroundColor = [UIColor yellowColor].CGColor;
sublayer.frame = CGRectMake(0, 300, self.view.frame.size.width, 100);
[self.view.layer addSublayer:sublayer];

This will set the color of view to yellow color in (0, 300, 320, 100)

`UITableView` delegate after `reloadData` is called

-(void) tableView:(UITableView *)tableView willDisplayCell:(UITableViewCell *)cell forRowAtIndexPath:(NSIndexPath *)indexPath
{
    if(indexPath.row == ((NSIndexPath*)[[tableView indexPathsForVisibleRows] lastObject]).row){
        NSLog(@"Finished loaded");
    }
}

Reference:

How to detect the end of loading of UITableView

Bold certain text on `UILabel`

// normal font
NSDictionary *attrs = [NSDictionary dictionaryWithObjectsAndKeys:
                       [UIFont fontWithName:@"Helvetica" size:20], NSFontAttributeName,
                       [UIColor whiteColor], NSForegroundColorAttributeName,
                       nil];
// bold font
NSDictionary *boldAttrs = [NSDictionary dictionaryWithObjectsAndKeys:
                          [UIFont fontWithName:@"Helvetica-Bold" size:20], NSFontAttributeName, nil];

NSString *text = @"The quick brown fox jumps over the lazy dog";

NSRange range = NSMakeRange(4, 15); // bold the text "quick brown fox"
// init with regular attributes
NSMutableAttributedString *textAttr = [[NSMutableAttributedString alloc] initWithString:text attributes:attrs];
[textAttr setAttributes:boldAttrs range:range]; // set specific attributes for range of text
[myLabel setAttributedText:textAttr];

NOTE: This is for iOS6 and above only

Reference:

Bold & Non-Bold Text In A Single UILabel?

Create class dynamically from string

1 2	NSString* className = @"MyClass"; [[NSClassFromString(className) alloc] init...];

Reference:

Create object from NSString of class name in Objective-C

Check is `nib` exists

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if([[NSBundle mainBundle] pathForResource:fileName ofType:@"nib"] != nil) {
    // nib exists
}

Reference:

Checking if a .nib or .xib file exists

- (void)shareText:(NSString *)string andImage:(UIImage *)image
{
    NSMutableArray *sharingItems = [NSMutableArray new];

    if (string) {
        [sharingItems addObject:string];
    }
    if (image) {
        [sharingItems addObject:image];
    }

    UIActivityViewController *activityController = [[UIActivityViewController alloc] initWithActivityItems:sharingItems applicationActivities:nil];
    [self presentViewController:activityController animated:YES completion:nil];
}

Reference:

How to display the default iOS 6 share action sheet with available share options?

Sort CoreData children objects

In MyParent.h

...
@property (nonatomic, retain) NSSet *children;

// add this
- (NSArray *)sortedChildren;

In MyParent.m

...
- (NSArray *)sortedChildren
{
    NSSortDescriptor *timestamp = [NSSortDescriptor sortDescriptorWithKey:@"timestamp" ascending:YES];
    return [[self.conversations allObjects] sortedArrayUsingDescriptors:[NSArray arrayWithObject:timestamp]];
}

Then you can now invoked by [myparent sortedChildren]

Reference:

Core data, sorting one-to-many child objects

Long press event on table row

- (void)viewDidLoad
{
    ...
    // add to the tableView instead of tableViewCell
    UILongPressGestureRecognizer *longPress = [[UILongPressGestureRecognizer alloc] initWithTarget:self action:@selector(tableViewPressed:)];
    [self.tableView addGestureRecognizer:longPress];
}

- (void)tableViewPressed:(UILongPressGestureRecognizer *)sender
{
    if (sender.state == UIGestureRecognizerStateBegan) { // only take action in this state
        CGPoint point = [sender locationInView:self.tableView]; // get the point (x, y)
        NSIndexPath *indexPath = [self.tableView indexPathForRowAtPoint:point]; // look for correct indexPath
        // in case you have section header
        CGFloat headerHeight = [self tableView:self.tableView heightForHeaderInSection:indexPath.section];
        
        // first row should be at the offset y which between (height of header view) and rowHeight + header for header view
        if ((point.y < headerHeight || point.y > (self.tableView.rowHeight + headerHeight)) && indexPath.row == 0) return;

        // do action here
    }
}

Clear CoreData tables

AppDelegate.m

- (void)flushDatabase
{
    [__managedObjectContext lock];
    NSArray *stores = [__persistentStoreCoordinator persistentStores];
    for(NSPersistentStore *store in stores) {
       [__persistentStoreCoordinator removePersistentStore:store error:nil];
       [[NSFileManager defaultManager] removeItemAtPath:store.URL.path error:nil];
    }
    [__managedObjectContext unlock];
    __managedObjectModel    = nil;
    __managedObjectContext  = nil;
    __persistentStoreCoordinator = nil;
}

Reference:

Clearing CoreData and all that inside

Compare `CGAffineTransform`

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if (CGAffineTransformEqualToTransform(transform, CGAffineTransformIdentity)) {
    // is equal
}

Reference:

How to Compare CGAffinetransform?

`UILabel` justify text to fit left & right

NSMutableParagraphStyle *paragraphStyles = [[NSMutableParagraphStyle alloc] init];
paragraphStyles.alignment = NSTextAlignmentJustified;
paragraphStyles.firstLineHeadIndent = 0.05;    // Very IMP

NSDictionary *attrs = [NSDictionary dictionaryWithObjectsAndKeys:
                       paragraphStyles, NSParagraphStyleAttributeName,
                       nil];

NSString *content = @"Lorem ipsum dolor sit amet, consectetur adipisicing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat. Duis aute irure dolor in reprehenderit in voluptate velit esse cillum dolore eu fugiat nulla pariatur. Excepteur sint occaecat cupidatat non proident, sunt in culpa qui officia deserunt mollit anim id est laborum.";
// Create the attributed string (text + attributes)
NSMutableAttributedString *textAttrs = [[NSMutableAttributedString alloc] initWithString:content attributes:attrs];

UILabel *justifiedLabel = [[UILabel alloc] initWithFrame:...];
justifiedLabel.numberOfLines = 0;
justifiedLabel.lineBreakMode = NSLineBreakByWordWrapping;
[justifiedLabel setAttributedText:textAttrs];
[justifiedLabel sizeToFit];
...

Reference:

NSTextAlignmentJustified to UILable textAligment on iOS6 will crash

`application:didReceiveRemoteNotification:` not called on app launching

During the first launch, this method will not be called, thus have to handle this manually

NSDictionary *remoteNotification = [launchOptions objectForKey: UIApplicationLaunchOptionsRemoteNotificationKey];
if (remoteNotification) {
    // call the method manually
    [self application:application didReceiveRemoteNotification:remoteNotification];
}

Reference:

Calling didReceiveRemoteNotification when app is launching for the first time

Both lines are required

1 2	[[UIApplication sharedApplication] setApplicationIconBadgeNumber: 0]; [[UIApplication sharedApplication] cancelAllLocalNotifications];

Reference:

iOS application: how to clear notifications?

Get version number

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2

NSString *version = [[NSBundle mainBundle] objectForInfoDictionaryKey: @"CFBundleShortVersionString"];
NSString *build = [[NSBundle mainBundle] objectForInfoDictionaryKey: (NSString *)kCFBundleVersionKey];

Reference:

How do I get the current version of my ios project in code?

`UISearchBar` flat color

// only apply for iOS 6
if ([[UIDevice currentDevice].systemVersion floatValue] < 7) {
    // go through the subview
    for (UIView *subview in self.searchBar.subviews) {
        if ([subview isKindOfClass:NSClassFromString(@"UISearchBarBackground")]) {
            // add a view filled with flat color to the background view
            UIView *flatView = [[UIView alloc] initWithFrame:subview.bounds];
            flatView.backgroundColor = [UIColor greenColor];
            [subview addSubview:flatView];
            break;
        }
    }
}

Reference:

How to apply a solid color to a UISearchBar

Add tap event to `UINavigationBar` title

UITapGestureRecognizer *titleViewTap = [[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(titleViewTapped:)];
UILabel *titleLabel = [[UILabel alloc] initWithFrame:CGRectMake(0, 0, 200, 40)];
// adjust to center
titleLabel.textAlignment = NSTextAlignmentCenter;
// standardize the text color, font
titleLabel.textColor = [[UINavigationBar appearance].titleTextAttributes valueForKey:UITextAttributeTextColor];
titleLabel.font = [[UINavigationBar appearance].titleTextAttributes valueForKey:UITextAttributeFont];
titleLabel.userInteractionEnabled = YES;
titleLabel.text = @"My awesome title";
[titleLabel addGestureRecognizer:titleViewTap];
self.navigationItem.titleView = titleLabel;

Then add a method

- (void)titleViewTapped:(UITapGestureRecognizer *)sender
{
    NSLog(@"user tapped");
}

Reference:

UINavigationBar Touch

UITableView separator on iOS7 show full width

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3

if ([tableView respondsToSelector:@selector(setSeparatorInset:)]) {
    [tableView setSeparatorInset:UIEdgeInsetsZero];
}

Reference:

How to fix UITableView separator on iOS 7? [duplicate]

Change UIImage default image color

UIImage *whiteIcon = [[UIImage imageNamed:@"WhiteIcon"] imageWithRenderingMode:UIImageRenderingModeAlwaysTemplate];

UIImageView *iconImageView = [[UIImageView alloc] initWithImage:whiteIcon];
iconImageView.tintColor = [UIColor grayColor];

Reference:

How can I change every color in a UIImage to gray? [closed]

Detect a shake event

Add the code below to your ViewController

-(void)motionBegan:(UIEventSubtype)motion withEvent:(UIEvent *)event
{
    if (motion == UIEventSubtypeMotionShake )
    {
        NSLog(@"Shake begin");
    }
}


-(void)motionEnded:(UIEventSubtype)motion withEvent:(UIEvent *)event
{
    if (motion == UIEventSubtypeMotionShake )
    {
        NSLog(@"Shake ended");
    }
}

Reference:

Objective C: Detecting a shake

Remove 1px gradient on top of `UITabBar`

1	[[UITabBar appearance] setShadowImage:[[UIImage alloc] init]];

Reference:

iOS UITabBar : Remove top shadow gradient line

Vibrate device

Import this AudioToolbox.framework from Link Binary With Library

1	#import <AudioToolbox/AudioServices.h>

Then, use either 1 of the following

1 2	AudioServicesPlayAlertSound(kSystemSoundID_Vibrate); AudioServicesPlaySystemSound(kSystemSoundID_Vibrate);

Reference:

Making the iPhone vibrate

Get reference counter in ARC mode

1	NSLog(@"Retain count is %ld", CFGetRetainCount((__bridge CFTypeRef)myObject));

Reference:

How do I verify reference count in ARC mode?

Hide the `UINavigationBar` back button

1	[self.navigationItem setHidesBackButton:YES animated:YES];

Reference:

How to hide the “back” button in UINavigationController?

Change `UIAlertView` keyboard type to numpad

1
2
3

alert.alertViewStyle = UIAlertViewStylePlainTextInput;
[[alert textFieldAtIndex:0] setKeyboardType:UIKeyboardTypeNumberPad];
[alert show];

The sequence is important

Reference:

UIAlertView: UIAlertViewStyleSecureTextInput: Numeric keyboard

Bad performance after adding shadow

When adding shadow effect to tableView/collectionView cell, the performance will drop significantly.

1	view.layer.shouldRasterize = YES;

Set the property above solve the issue

Reference:

I Have bad performance on using shadow effect

`UICollectionViewCell` subclass init never run

Implement in initWithFrame: instead

Reference:

UICollectionViewCell subclass init never run

Take screenshot from UIView

- (UIImage *)screenshotImageFromView:(UIView *)view {
    
    UIGraphicsBeginImageContextWithOptions(view.bounds.size, 1, 0.0f);
    
    [view.layer renderInContext:UIGraphicsGetCurrentContext()];
    
    UIImage *image = UIGraphicsGetImageFromCurrentImageContext();
    
    UIGraphicsEndImageContext();

    return image;
}

// usage
UIImage *img = [self screenshotImageFromView:self.view];

`UIColor` from hex string

Add a macro in <Project>-Prefix.pch

#define UIColorFromRGB(rgbValue) [UIColor \
colorWithRed:((float)((rgbValue & 0xFF0000) >> 16))/255.0 \
green:((float)((rgbValue & 0xFF00) >> 8))/255.0 \
blue:((float)(rgbValue & 0xFF))/255.0 alpha:1.0]

Then add a helper function

- (unsigned int)intFromHexString:(NSString *) hexStr
{
    unsigned int hexInt = 0;

    // Create scanner
    NSScanner *scanner = [NSScanner scannerWithString:hexStr];

    // Tell scanner to skip the # character
    [scanner setCharactersToBeSkipped:[NSCharacterSet characterSetWithCharactersInString:@"#"]];

    // Scan hex value
    [scanner scanHexInt:&hexInt];

    return hexInt;
}

Usage

1	UIColor *color = UIColorFromRGB([self intFromHexString:@"#ff3366"]);

References:

LocationService not working on iOS8

1
2
3

if ([_locationManager respondsToSelector:@selector(requestWhenInUseAuthorization)]) {
    [_locationManager requestWhenInUseAuthorization];
}

Call this method before startUpdatingLocation.

In the Info.plist, add

1 2	<key>NSLocationWhenInUseUsageDescription</key> <string>You are required to enable the location service to get accurate results.</string>

Reference:

iOS 8 : Location Services not working

`CLPlacemark.administrativeArea` Malaysia list

Selangor
Negri Sembilan
KL
Kedah
Pinang
Perak
Perlis
Malacca
Johore
Pahang
Terengganu
Kelantan
Sabah
Sarawak
Wilayah Persekutuan Labuan

Change `UITextField` placeholder color

if ([textField respondsToSelector:@selector(setAttributedPlaceholder:)]) {
    UIColor *color = [UIColor colorWithWhite:1 alpha:0.7];
    textField.attributedPlaceholder = [[NSAttributedString alloc] initWithString:@"Placeholder text" attributes:@{NSForegroundColorAttributeName: color}];
} else {
    TSLog(@"Cannot set placeholder text's color, because deployment target is earlier than iOS 6.0");
}

Reference:

iPhone UITextField - Change placeholder text color

Underline text on `UIButton`

UIButton *button = [UIButton buttonWithType:UIButtonTypeCustom];
button.titleLabel.textColor = [UIColor whiteColor];
button.backgroundColor = [UIColor clearColor];
NSMutableAttributedString *buttonStr = [[NSMutableAttributedString alloc] initWithString:@"or do other stuff"];
[buttonStr addAttribute:NSUnderlineStyleAttributeName value:[NSNumber numberWithInteger:NSUnderlineStyleSingle] range:NSMakeRange(3, [buttonStr length] - 3)];
[button setAttributedTitle:buttonStr forState:UIControlStateNormal];

The code above will underline do other stuff.

Reference:

UIButton Or UILabel with underlined text. iOS 6 or iOS 7

Loop through `NSDate`

- (void)dateRangeFrom:(NSDate *)fromDate to:(NSDate *)toDate
{
    // add 1 day to them, e.g.
    // fromDate = 2014-11-05 ; toDate = 2014-10-30, without adding 1 day, it will loop from 2014-11-04 to 2014-10-29
    fromDate = [fromDate dateByAddingTimeInterval:24 * 60 * 60];
    toDate = [toDate dateByAddingTimeInterval:24 * 60 * 60];

    NSDateComponents *component = [NSDateComponents new];
    
    // if fromDate is greater than toDate, then loop decending, ascending otherwise
    NSComparisonResult compareResult;
    if ([fromDate compare:toDate] == NSOrderedAscending) {
        compareResult = NSOrderedAscending;
        component.day = 1; // loop through day by day
    } else {
        compareResult = NSOrderedDescending;
        component.day = -1;
    }
    
    NSCalendar *currentCalendar = [NSCalendar currentCalendar];
    
    while ([fromDate compare:toDate] == compareResult) {
        fromDate = [currentCalendar dateByAddingComponents:component toDate:fromDate options:0];
        NSLog(@"Date %@", fromDate);
    }
}

Reference:

Loop between two NSDates in Objective C [closed]

Add touch event on `UIStatusBar`

AppDelegate.h

1	static NSString * const kStatusBarTappedNotification = @"statusBarTappedNotification";

AppDelegate.m

#pragma mark - Status bar touch tracking
- (void) touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event {
    [super touchesBegan:touches withEvent:event];
    CGPoint location = [[[event allTouches] anyObject] locationInView:[self window]];
    CGRect statusBarFrame = [UIApplication sharedApplication].statusBarFrame;
    if (CGRectContainsPoint(statusBarFrame, location)) {
        [self statusBarTouchedAction];
    }
}

- (void)statusBarTouchedAction {
    [[NSNotificationCenter defaultCenter] postNotificationName:kStatusBarTappedNotification
                                                        object:nil];
}

AnyViewController.m

- (void)viewWillAppear:(BOOL)animated
{
    [super viewWillAppear:animated];
    
    [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(statusBarTappedAction:) name:kStatusBarTappedNotification object:nil];
}

- (void)viewWillDisappear:(BOOL)animated
{
    [super viewWillDisappear:animated];
    
    [[NSNotificationCenter defaultCenter] removeObserver:self name:kStatusBarTappedNotification object:nil];
}

- (void)statusBarTappedAction:(NSNotification*)notification
{
    NSLog(@"StatusBar tapped");
}

Reference:

How to detect touches in status bar

Detect link on `UITextView`

textView.editable = NO;
textView.dataDetectorTypes = UIDataDetectorTypeAll;
if ([textView respondsToSelector:@selector(setLinkTextAttributes:)]) {
    textView.linkTextAttributes = @{NSForegroundColorAttributeName: [UIColor redColor]};
}

Reference:

How to make URL/Phone-clickable UILabel?

Get rotation angle from `CGAffineTransform`

1	atan2(transform.b, transform.a);

NOTE: The value are in radian

Reference:

iphone sdk CGAffineTransform getting the angle of rotation of an object

Update status bar background color, fade when scroll

@implementation ViewController {
    UIView *_statusBarBackgroundView;
}

- (void)viewDidLoad {
    ...
    _statusBarBackgroundView = [[UIView alloc] initWithFrame:[[UIApplication sharedApplication] statusBarFrame]];
    _statusBarBackgroundView.backgroundColor = [UIColor clearColor];
    [self.view addSubview:_statusBarBackgroundView];
}

#pragma mark - UIScrollViewDelegate
- (void)scrollViewDidScroll:(UIScrollView *)scrollView
{
    CGFloat offset = scrollView.contentOffset.y;
    CGFloat initialPoint = 40;
    CGFloat endPoint = 80;
    
    if (offset > initialPoint) {
        CGFloat opacity = (offset - initialPoint) / (endPoint - initialPoint);
        opacity = MIN(opacity, 1);
        _statusBarBackgroundView.backgroundColor = UIColorFromRGBA(0xfc8d8d, opacity);
    } else {
        _statusBarBackgroundView.backgroundColor = [UIColor clearColor];
    }
    self.navigationController.navigationBar.backgroundColor = _statusBarBackgroundView.backgroundColor;
}

Reference:

iOS7 Side menu status bar color transition. As in the iOS7 Facebook App

`UIWebView` inject css

- (void)webViewDidFinishLoad:(UIWebView *)webView
{
    NSString* css = @"\"@font-face { font-family: 'Chalkboard'; src: local('ChalkboardSE-Regular'); } body { background-color: #F0F0FC; color: #572B00; font-family: Chalkboard;} a { color: #A00; text-decoration: none;}\"";
    NSString* js = [NSString stringWithFormat:
                @"var styleNode = document.createElement('style');\n"
                 "styleNode.type = \"text/css\";\n"
                 "var styleText = document.createTextNode(%@);\n"
                 "styleNode.appendChild(styleText);\n"
                 "document.getElementsByTagName('head')[0].appendChild(styleNode);\n",css];
    NSLog(@"js:\n%@",js);
    [self.webView stringByEvaluatingJavaScriptFromString:js];
}

Reference:

UIWebView CSS injection using JavaScript

`UIImagePickerControllerOriginalImage` orientation issue

+ (UIImage*)removeOrientationForImage:(UIImage*)image {
    CGSize size = image.size;
    UIGraphicsBeginImageContext(size);
    [image drawInRect:CGRectMake(0,0,size.width ,size.height)];
    UIImage* newImage = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();

    return newImage;
}

Reference:

How to Rotate a UIImage 90 degrees?

`DAKeyboardControl` issue with UITabBar

[contentView addKeyboardPanningWithActionHandler:^(CGRect keyboardFrameInView, BOOL opening, BOOL closing) {
    
    CGRect toolBarFrame = toolBar.frame;
    toolBarFrame.origin.y = MIN(keyboardFrameInView.origin.y, contentView.bounds.size.height) - toolBarFrame.size.height;
    toolBar.frame = toolBarFrame;
    
    CGRect tableViewFrame = tableView.frame;
    tableViewFrame.size.height = toolBarFrame.origin.y;
    tableView.frame = tableViewFrame;
}];

Reference:

Dismissing the keyboard with tab bar layout makes the input view disappear #42

`NSArray` extract a single column into another array

e.g.

[
    {
        "id": "1",
        "name": "Foo"
    },
    {
        "id": "2",
        "name": "Bar"
    },
    {
        "id": "3",
        "name": "Foo Bar"
    },
]

After calling

1	[myArr mutableArrayValueForKey:@"name"]

New result

1	["Foo", "Bar", "Foo Bar"]

`MKMapView` event after dragged/zoomed

1	- (void)mapView:(MKMapView *)mapView regionDidChangeAnimated:(BOOL)animated;

Reference:

determine if MKMapView was dragged/moved

Custom `UIResponder` trigger event

Example, create a CustomCheckbox, want to perform ValueChanged event when touched on the checkbox

CustomCheckbox.m

- (BOOL)beginTrackingWithTouch:(UITouch *)touch withEvent:(UIEvent *)event
{
    self.checked = !_checked;
    // trigger value changed event
    [self sendActionsForControlEvents:UIControlEventValueChanged];
    return YES;
}

ViewController.m

1	[checkbox addTarget:self action:@selector(checkboxChecked:) forControlEvents:UIControlEventValueChanged];

Reference:

Custom Controls

Print out properties of an object

#import <objc/message.h>

- (NSString *)descriptionForObject:(id)objct
{
    unsigned int varCount;
    NSMutableString *descriptionString = [[NSMutableString alloc]init];
    
    
    objc_property_t *vars = class_copyPropertyList(object_getClass(objct), &varCount);
    
    for (int i = 0; i < varCount; i++)
    {
        objc_property_t var = vars[i];
        
        const char* name = property_getName (var);
        
        NSString *keyValueString = [NSString stringWithFormat:@"\n%@ = %@",[NSString stringWithUTF8String:name],[objct valueForKey:[NSString stringWithUTF8String:name]]];
        [descriptionString appendString:keyValueString];
    }
    
    free(vars);
    return descriptionString;
}

Usage: NSLog(@"obj %@", [self descriptionForObject:obj]);

Reference:

Github: arundevma/ICHObjectPrinter

AFNetworking

Check is offline

[[AFNetworkReachabilityManager sharedManager] startMonitoring];
[[AFNetworkReachabilityManager sharedManager] setReachabilityStatusChangeBlock:^(AFNetworkReachabilityStatus status) {
    NSLog(@"Reachability: %@", AFStringFromNetworkReachabilityStatus(status));
    switch (status) {
        case AFNetworkReachabilityStatusReachableViaWWAN:
        case AFNetworkReachabilityStatusReachableViaWiFi:
            NSLog(@"online");
            break;
        case AFNetworkReachabilityStatusNotReachable:
        default:
            NSLog(@"offline");
            break;
    }
}];

Reference:

AFNetworking 2.0 queue request when device is offline with setReachabilityStatusChangeBlock does nothing

Animation

Flip animation between view controllers

Present

1 2	viewController.modalTransitionStyle = UIModalTransitionStyleFlipHorizontal; [self presentViewController:viewController animated:YES completion:nil];

Dismiss

1	[self dismissViewControllerAnimated:YES completion:nil];

Reference:

How to do the flip animation between two UIViewControllers while clicking info button?

Move object from bottom to top

// set the initial position
UIImageView *imageView = [[UIImageView alloc] initWithFrame:CGRectMake(40, 320, 240, 100)];
...

[UIView animateWithDuration:1.0 // 1 second
                      delay:0.0
                    options:UIViewAnimationOptionCurveLinear
                 animations:^{
                     // move the image to top
                     imageView.center = CGPointMake(imageView.center.x, 100);
                 }
                 completion:nil];

Fade in UIButton

UIButton *fooButton = [UIButton buttonWithType:UIButtonTypeCustom];
fooButton.frame = ...;
fooButton.alpha = 0; // set to transparent first

[UIView animateWithDuration:0.5 // 0.5 second
                      delay:0.0
                    options:UIViewAnimationOptionCurveLinear
                 animations:^{
                     fooButton.alpha = 1.0; // slowly fade in
                 }
                 completion:nil];

Reference:

Fading in and out UIButton in view

Flip animation between 2 views

[UIView beginAnimations:nil context:NULL];
[UIView setAnimationDuration:1.0];
[UIView setAnimationTransition:UIViewAnimationTransitionFlipFromRight forView:self.view cache:NO];

// optional: event handler after animation
[UIView setAnimationDelegate:self];
[UIView setAnimationDidStopSelector:@selector(viewFlipped)];

int listViewIndex = [self.view.subviews indexOfObject:self.tableView];
int mapViewIndex = [self.view.subviews indexOfObject:self.mapView];

if (listViewIndex > mapViewIndex)
{
    sender.title = @"List";
    [self.view bringSubviewToFront:self.mapView];
}
else
{
    sender.title = @"Map";
    [self.view bringSubviewToFront:self.tableView];
}

[UIView commitAnimations];

If you added the event handler, just add the code below

- (void)viewFlipped
{
    NSLog(@"Flip animation completed.");
}

References:

Facebook

Force user to allow `publish_actions` permission

@implementation MyViewController {
    NSString *fbToken;
}

...

// when tapped on facebook button
- (IBAction)facebookTouched:(UIButton *)sender
{
    // We will request the user's public profile and the user's birthday
    // These are the permissions we need:
    NSArray *permissionsNeeded = @[@"publish_actions", @"email"];
    
    // don't cache the token
    FBSession *mySession = [[FBSession alloc] initWithAppID:nil permissions:permissionsNeeded urlSchemeSuffix:nil tokenCacheStrategy:[FBSessionTokenCachingStrategy nullCacheInstance]];
    
    [mySession openWithCompletionHandler:^(FBSession *session,
                                                     FBSessionState status,
                                                     NSError *error) {
        
        UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"Facebook Error" message:@"You must allow Facebook permissions" delegate:nil cancelButtonTitle:@"OK" otherButtonTitles:nil];

        if (error) { // user not allow "email"
            [alert show];
        } else {
            
            // i don't know what is this for, if without this line, this block will be executed 2 times and get error
            if (status == 258) return;
            
            [FBSession setActiveSession:session];
            
            // Request the permissions the user currently has
            [FBRequestConnection startWithGraphPath:@"/me/permissions"
                                  completionHandler:^(FBRequestConnection *connection, id result, NSError *error) {
                                      if (!error) {
                                          // These are the current permissions the user has:
                                          NSDictionary *currentPermissions = [(NSArray *)[result data] objectAtIndex:0];
                                          
                                          // We will store here the missing permissions that we will have to request
                                          NSMutableArray *requestPermissions = [[NSMutableArray alloc] initWithArray:@[]];
                                          
                                          // Check if all the permissions we need are present in the user's current permissions
                                          // If they are not present add them to the permissions to be requested
                                          for (NSString *permission in permissionsNeeded){
                                              if (![currentPermissions objectForKey:permission]){
                                                  [requestPermissions addObject:permission];
                                              }
                                          }
                                          
                                          // If we have more permissions to request
                                          if ([requestPermissions count] > 0) { // user haven't allow publish_actions
                                              [alert show];
                                          } else {
                                              fbToken = session.accessTokenData.accessToken;
                                          }
                                          
                                      } else {
                                          // An error occurred, we need to handle the error
                                          // See: https://developers.facebook.com/docs/ios/errors
                                          NSLog(@"error %@", error.description);
                                      }
                                  }];
        }
    }];
}

Get profile picture

// set image & user name
[FBSession setActiveSession:self.session];
[[FBRequest requestForMe] startWithCompletionHandler:^(FBRequestConnection *connection, NSDictionary<FBGraphUser> *FBuser, NSError *error) {
    if (error) {
        NSLog(@"error %@", error.description);
    } else {
        self.usernameLabel.text = [FBuser name];
        [self.avatarImageView setImageWithURL:[NSURL URLWithString:[NSString stringWithFormat:@"https://graph.facebook.com/%@/picture?height=100&type=normal&width=100", [FBuser username]]]];
    }
}];

Reference:

Getting username and profile picture from Facebook iOS 7

FacebookSDK 4.x

ViewController.m

#import <FBSDKCoreKit/FBSDKCoreKit.h>
#import <FBSDKLoginKit/FBSDKLoginKit.h>

- (void)facebookButtonTapped:(id)sender
{
    FBSDKLoginManager *loginManager = [[FBSDKLoginManager alloc] init];
    [loginManager logInWithReadPermissions:@[@"email"] handler:^(FBSDKLoginManagerLoginResult *result, NSError *error) {
        if (error) {
            NSLog(@"Facebook error: %@", [error localizedDescription]);
            return;
        }
        NSLog(@"Facebook token: %@", result.token.tokenString);
    }];
}

AppDelegate.m

#import <FBSDKCoreKit/FBSDKCoreKit.h>

...
- (void)applicationDidBecomeActive:(UIApplication *)application
{
    // Restart any tasks that were paused (or not yet started) while the application was inactive. If the application was previously in the background, optionally refresh the user interface.
    [FBSDKAppEvents activateApp];
}

- (BOOL)application:(UIApplication *)application openURL:(NSURL *)url sourceApplication:(NSString *)sourceApplication annotation:(id)annotation {
    return [[FBSDKApplicationDelegate sharedInstance] application:application
                                                          openURL:url
                                                sourceApplication:sourceApplication
                                                       annotation:annotation];
}

Objective-C

String casting

Reference:

Dump object in console

Reference:

Type casting

Reference:

Accessing a deep element in JSON

Clear all cookies

Reference:

Clear all NSUserDefaults

Reference:

Define global constant

Reference:

Add objects into NSMutableArray

Reference:

Add objects into NSMutableDictionary

Reference:

set border to image

Reference:

NSDate & Unix timestamp

References:

Hide the navigation bar

Reference:

Property creation

Dismiss presentModalViewController

Reference:

UILabel setFont

Reference:

UILabel center text alignment

Reference:

Get device model

Reference:

Get user location

Reference:

Add beep sound

Reference:

Bind Return button to UITextField

Reference:

Change keyboard Return key to Go

Reference:

Delegate multiple UITextField

Reference:

UIScrollView scroll as page

Change the height of UITableViewCell

Reference:

Set UITableViewCell background image

Set background on UIButton

Remove UITableView cell separator

Reference:

Reset UIBarButtonItem background to default

Get Day, Month, Year from NSDate

Reference:

Create UITableView programmatically

Validate phone number via Regex

Validate required text field

Reference:

Disable sleep

Reference:

Adding criteria to CoreData

Reference:

Sentence to CamelCase

Reference:

Add touch event to UIImageView

NSArray check is object in array

Reference:

Set timeout interval

Reference:

Compare CGRect

Reference:

Open browser when click on hyperlink in UIWebView

Reference:

Access property variable in closure

Reference:

Add a Done button to UISearchBar

Reference:

Change UISearchBar Search button to Done

Reference:

Remove all subviews from UIScrollView

Accessing a `deep` element in JSON

Dismiss `presentModalViewController`

Bind `Return` button to UITextField

Change keyboard `Return` key to `Go`

Get `Day`, `Month`, `Year` from NSDate

RSA - Convert `.pem` to `.der` format

Change textLabel color of UITableViewCell in `selected` state

Detect `double tap` event on UIImageView

`UISegmentedControl` deselect segment

`UISegmentedControl` change text & border color

Add `UISegmentedControl` to `UIToolbar`

Use custom font in `UIWebView`