UIAlertViewDelegate on Category for UIViewController

----------- .h file ------------------------------------------------

static void *MCDAlertViewCodeBlockKey = &MCDAlertViewCodeBlockKey;

@interface UIViewController (MCDAlertViewDelegate) <UIAlertViewDelegate>

@end

---------- .m file -------------------------------------------------
#import <objc/runtime.h>

@implementation UIViewController (MCDAlertViewDelegate)

# pragma mark - UIAlertViewDelegate instance methods (UIALERTVIEWDELEGATE)

- (void)alertView:(UIAlertView *)alertView clickedButtonAtIndex:(NSInteger)buttonIndex
{
    void (^block)(NSInteger) = objc_getAssociatedObject(alertView, MCDAlertViewCodeBlockKey);
    // 'block' is always NULL so the delegate is called by the 'alertView' does not have the block of code any longer
    if (block) {
        block(buttonIndex);
    }
}

@end

-------- Some UIViewController .m file -----------------------------------------------------
#import "UIViewController+MCDAlertViewDelegate"


- (void)showAlert
{
UIAlertView *alert = [[UIAlertView alloc]
                          initWithTitle:NSLocalizedString(@"Report Data Loss", nil)
                          message:NSLocalizedString(@"You will lose all report data. Are you sure?", nil)
                          delegate:self
                          cancelButtonTitle:NSLocalizedString(@"No", nil)
                          otherButtonTitles:NSLocalizedString(@"Yes", nil),
                          nil];

    objc_setAssociatedObject(alert, MCDAlertViewCodeBlockKey, ^(NSInteger buttonIndex) {
        if (buttonIndex == 1) {
            // Do something since they clicked "YES" button
            
            // Never getting into this portion of the code
        }
    }, OBJC_ASSOCIATION_COPY);
    [alert show];
}