How do I handle the actions of a UIAlertController?

Question

How can I link UIAlertController alert action buttons with action handlers using objective-c? I'm using Xcode 7.1.

Here is my code:

- (IBAction)selectbtn:(UIButton *)sender {

    UIAlertController *alert=[ UIAlertController alertControllerWithTitle:@"NEW" message:@"button pressed" preferredStyle:UIAlertControllerStyleActionSheet];
    UIAlertAction *cameraaction=[UIAlertAction actionWithTitle:@"From camera" style:UIAlertActionStyleDefault handler:nil ];
    [alert addAction:cameraaction];
    UIAlertAction *libraryaction=[UIAlertAction actionWithTitle:@"From photo library" style:UIAlertActionStyleDefault handler:nil ];
    [alert addAction:libraryaction];
    UIAlertAction *cancelaction=[UIAlertAction actionWithTitle:@"cancel" style:UIAlertActionStyleDestructive handler:nil];
    [alert addAction:cancelaction];
    [self presentViewController:alert animated:YES
                     completion:nil];
    }

Answer 1

Objective-C

UIAlertController works like this:

UIAlertController *alert = [UIAlertController alertControllerWithTitle:@"Title" message:@"text mssg" preferredStyle:UIAlertControllerStyleAlert];
UIAlertAction *okAction = [UIAlertAction actionWithTitle:@"Ok" style:UIAlertActionStyleDefault handler:^(UIAlertAction * action){
    // Ok action example
}];
UIAlertAction *otherAction = [UIAlertAction actionWithTitle:@"Other" style:UIAlertActionStyleDefault handler:^(UIAlertAction * action){
    // Other action
}];
[alert addAction:okAction];
[alert addAction:otherAction];
[self presentViewController:alert animated:YES completion:nil];

I think you meant that.

Swift 3.0/4.0

let myalert = UIAlertController(title: "Titulo mensaje", message: "Mi mensaje.", preferredStyle: UIAlertControllerStyle.alert)

myalert.addAction(UIAlertAction(title: "Aceptar", style: .default) { (action:UIAlertAction!) in
        print("Selected")
    })
myalert.addAction(UIAlertAction(title: "Cancelar", style: .cancel) { (action:UIAlertAction!) in
        print("Cancel")
    })
    
    self.present(myalert, animated: true)

Swift 5

  let myalert = UIAlertController(title: "Titulo mensaje", message: "Mi mensaje.", preferredStyle: UIAlertController.Style.alert)

    myalert.addAction(UIAlertAction(title: "Aceptar", style: .default) { (action:UIAlertAction!) in
            print("Selected")
        })
    myalert.addAction(UIAlertAction(title: "Cancelar", style: .cancel) { (action:UIAlertAction!) in
            print("Cancel")
        })

        self.present(myalert, animated: true)

Answer 2

You can add any code you want in the handler of the action method, sample code can be like this:

@interface ViewController () <UIImagePickerControllerDelegate, UINavigationControllerDelegate>
@property (weak, nonatomic) IBOutlet UIImageView *imageView;
@property (strong, nonatomic) UIAlertController *alertCtrl;
@property (strong, nonatomic) UIImagePickerController *imagePicker;
@end

@implementation ViewController

- (void)viewDidLoad
{
    [super viewDidLoad];
    [self setupAlertCtrl];
}

- (void) setupAlertCtrl
{
    self.alertCtrl = [UIAlertController alertControllerWithTitle:@"Select Image"
                                                         message:nil
                                                  preferredStyle:UIAlertControllerStyleActionSheet];
    //Create an action
    UIAlertAction *camera = [UIAlertAction actionWithTitle:@"From camera"
                                                     style:UIAlertActionStyleDefault
                                                   handler:^(UIAlertAction *action)
                                                    {
                                                        [self handleCamera];
                                                    }];
    UIAlertAction *imageGallery = [UIAlertAction actionWithTitle:@"From Photo Library"
                                                     style:UIAlertActionStyleDefault
                                                   handler:^(UIAlertAction *action)
                                                    {
                                                        [self handleImageGallery];
                                                    }];
    UIAlertAction *cancel = [UIAlertAction actionWithTitle:@"Cancel"
                                                           style:UIAlertActionStyleCancel
                                                         handler:^(UIAlertAction *action)
                                   {
                                       [self dismissViewControllerAnimated:YES completion:nil];
                                   }];


    //Add action to alertCtrl
    [self.alertCtrl addAction:camera];
    [self.alertCtrl addAction:imageGallery];
    [self.alertCtrl addAction:cancel];


}

- (IBAction)selectImagePressed:(UIButton *)sender
{
    [self presentViewController:self.alertCtrl animated:YES completion:nil];
}

- (void)handleCamera
{
#if TARGET_IPHONE_SIMULATOR
    UIAlertController *alert = [UIAlertController alertControllerWithTitle:@"Error"
                                                                   message:@"Camera is not available on simulator"
                                                            preferredStyle:UIAlertControllerStyleAlert];

    UIAlertAction *ok = [UIAlertAction actionWithTitle:@"OK"
                                                 style:UIAlertActionStyleDefault
                                               handler:^(UIAlertAction *action)
                                                {
                                                    [self dismissViewControllerAnimated:YES completion:nil];
                                                }];

    [alert addAction:ok];
    [self presentViewController:alert animated:YES completion:nil];
#elif TARGET_OS_IPHONE
    //Some code for iPhone
    self.imagePicker = [[UIImagePickerController alloc] init];
    self.imagePicker.delegate = self;
    self.imagePicker.sourceType = UIImagePickerControllerSourceTypeCamera;
    [self presentViewController:self.imagePicker animated:YES completion:nil];

#endif
}

- (void)handleImageGallery
{
    self.imagePicker = [[UIImagePickerController alloc] init];
    self.imagePicker.sourceType = UIImagePickerControllerSourceTypePhotoLibrary;
    self.imagePicker.delegate = self;
    [self presentViewController:self.imagePicker animated:YES completion:nil];
}

- (void)imagePickerController:(UIImagePickerController *)picker didFinishPickingMediaWithInfo:(NSDictionary *)info
{
    NSData *dataImage = UIImageJPEGRepresentation([info objectForKey:@"UIImagePickerControllerOriginalImage"],1);
    UIImage *img = [[UIImage alloc] initWithData:dataImage];
    [self.imageView setImage:img];
    [self.imagePicker dismissViewControllerAnimated:YES completion:nil];

}

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