当变量为控制器的实例时 也会出现循环引用例如abc @interface ViewController ()<UITableViewDelegate,UITableViewDataSource> { UITableView *_tableView; NSString *abc; }

1.如果此时的block不属于self 则直接赋值(在VC在dealloc前 必须要销毁block回调 否则内存泄漏) 例如添加在keywindow上的View：

• (void)viewDidLoad { [super viewDidLoad];

  AView *view = [[AView alloc] init]; view.frame = CGRectMake(100, 100, 100, 100); view.backgroundColor = [UIColor redColor]; view.abc = ^(NSString *aaa){

  abc = aaa;复制代码

  }; AppDelegate *delegate = (AppDelegate *)[UIApplication sharedApplication].delegate; UIWindow *keywindow = delegate.window; [keywindow addSubview:view]; [view removeFromSuperview];

//这样写block也不属于self void(^foo)(NSStringstr)= ^(NSString str){

abc = str;};foo(@"1111");复制代码

}

2.如果此时的block属于self 则要写方法赋值赋值 例如添加在self.view上的View：

• (void)viewDidLoad { [super viewDidLoad];

  __weak typeof(self) weakSelf = self; AView *view = [[AView alloc] init]; view.frame = CGRectMake(100, 100, 100, 100); view.backgroundColor = [UIColor redColor]; view.abc = ^(NSString *aaa){ [weakSelf setAbc:aaa]; }; [self.view addSubview:view]; }

-(void)setAbc:(NSString *)a{

abc = a;复制代码

}