iOS关联对象

iOSAssociatedObject.m

#import "ViewController.h"
#import <objc/runtime.h>

@interface ViewController () <UIAlertViewDelegate>

@end

static void *MyAlertViewKey = "MyAlertViewKey";

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    // Do any additional setup after loading the view, typically from a nib.
    
    UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"Question"
                                                    message:@"What do you want to do?"
                                                   delegate:self
                                          cancelButtonTitle:@"Cancel"
                                          otherButtonTitles:@"Continue", nil];
    
    void (^block)(NSInteger) = ^(NSInteger buttonIndex){
        if (buttonIndex == 0) {
            NSLog(@"cancel");
        } else {
            NSLog(@"continue");
        }
    };
    
    objc_setAssociatedObject(alert, MyAlertViewKey, block, OBJC_ASSOCIATION_COPY);
    
    [alert show];
}

- (void)didReceiveMemoryWarning {
    [super didReceiveMemoryWarning];
    // Dispose of any resources that can be recreated.
}

#pragma mark - alert view delegate
- (void)alertView:(UIAlertView *)alertView clickedButtonAtIndex:(NSInteger)buttonIndex
{
    void (^block)(NSInteger) = objc_getAssociatedObject(alertView, MyAlertViewKey);
    block(buttonIndex);
}

@end