block重新赋值后判断是否相等

@property (nonatomic, copy)  void(^block)();

- (void)viewDidLoad {
    [super viewDidLoad];
    self.block = ^{
        NSLog(@"123");
    };
    void * a = (__bridge void *)(_block);
    dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(1 * NSEC_PER_SEC)), dispatch_get_main_queue(), ^{
        if (a == _block) {
            self.block();
        }
    });
    self.block = ^{
        NSLog(@"456");
    };
}

不输出

@property (nonatomic, copy)  void(^block)();

- (void)viewDidLoad {
    [super viewDidLoad];
    self.block = ^{
        NSLog(@"123");
    };
    void * a = (__bridge void *)(_block);
    dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(1 * NSEC_PER_SEC)), dispatch_get_main_queue(), ^{
        if (a == _block) {
            self.block();
        }
    });
}

输出 123