Question

I have a function that shows a UIAlertView with YES/NO buttons, and it is used only inside the function’s scope so I dont want to implement a delegation to catch the user feedback.

Is there any way to know what button users clicked without implement UIAlertViewDelegate, something like:

[alert show];
if([alert indexOfClickedButton] == indexOfYes)
{
....
}

Or lambda expression as in Animation

Answer 1

There is no way to avoid delegation completely, but you could create a wrapper to that effect along these lines:

@interface MyAlertViewDelegate : NSObject<UIAlertViewDelegate>

typedef void (^AlertViewCompletionBlock)(NSInteger buttonIndex);
@property (strong,nonatomic) AlertViewCompletionBlock callback;

+ (void)showAlertView:(UIAlertView *)alertView withCallback:(AlertViewCompletionBlock)callback;

@end


@implementation MyAlertViewDelegate
@synthesize callback;

- (void)alertView:(UIAlertView *)alertView clickedButtonAtIndex:(NSInteger)buttonIndex {
    callback(buttonIndex);
}

+ (void)showAlertView:(UIAlertView *)alertView
         withCallback:(AlertViewCompletionBlock)callback {
    __block MyAlertViewDelegate *delegate = [[MyAlertViewDelegate alloc] init];
    alertView.delegate = delegate;
    delegate.callback = ^(NSInteger buttonIndex) {
        callback(buttonIndex);
        alertView.delegate = nil;
        delegate = nil;
    };
    [alertView show];
}

@end

(ARC is assumed, if you are not using it change delegate = nil to [delegate release].)

Usage would be something like:

UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"Confirm" message:@"Yes or No?" delegate:nil cancelButtonTitle:@"Cancel" otherButtonTitles:@"Yes",@"No", nil];
[MyAlertViewDelegate showAlertView:alert withCallback:^(NSInteger buttonIndex) {
    // code to take action depending on the value of buttonIndex
}];