为什么委托不起作用？ iOS - 目标 C

Question

I have the following class:

@interface myClass : NSObject <UIAlertViewDelegate>

@property (strong) UIAlertView *alert;

-(void) displayAlert;
@end

And here the implementation:

#include "myClass.hpp"

@implementation myClass


- (instancetype)init
{
    self = [super init];
    if (self) {
       [self displayAlert];
    }
    return self;
}

- (void)displayAlert{
    dispatch_async(dispatch_get_main_queue(), ^(void){

_alert = [[UIAlertView alloc] initWithTitle:@"title"
                                                                       message:@"body"
                                                                      delegate:self
                                                             cancelButtonTitle:@"YES"
                                                             otherButtonTitles:nil,nil];
                       [_alert show];
    });

}

- (void)alertView:(UIAlertView *)alertView didDismissWithButtonIndex:(NSInteger)buttonIndex {
   //This method is never called
}
@end

And I create obj of this class this way:

MyClass *myClass = [MyClass new];

It displays the alert but it don't call the callback function after button click.

Answer 1

You need to retain the "myClass" variable until at least after the button is tapped, else it will be deallocated and the delegate method would then not be triggered.