Block如何避免self retain

来源：互联网发布：计算圆周率的算法编辑：程序博客网时间：2024/06/05 15:51

http://stackoverflow.com/questions/3975675/objective-c-blocks-is-there-a-way-to-avoid-self-being-retained

从以上的讨论中,我没没有办法让block引用参数而不导致selfretain的方法,但是提到了三种方式来实现在block中引用参数而不导致self retain的解决方案:

1 将当前对象当做block的参数传进去,其形式:

[request getRaidersFrompageNum:pageNum finished:^(id target,id result, ServerResponseState state)

{

[(RaidersViewController *)target getRaidersInfoAndShow:state response:result pageNum:pageNum];

}];

其中target就是当前对象self,这种调用的方法完全类似于delegate的调用,target(self)被当成局部变量来使用,所以self不会retain

2. 调用大度的方法来调用(release/dealloc),类似于timer 的 invalidate 方法(不过我还没想通怎么使用这种方法,所以不再举例子)

3. 使用__block转换变量,形式:

- (void)blockTimer

{

__block TestViewController *blockSelf = self;

dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{

blockSelf->_timer=[NSTimer scheduledTimerWithTimeInterval:1.0

target:blockSelf

selector:@selector(caculateLeftTimeForTomorrow)

userInfo:nil

repeats:YES] ;

[[NSRunLoop currentRunLoop] addTimer:blockSelf->_timer forMode:NSDefaultRunLoopMode];

[[NSRunLoop currentRunLoop] run];

});

}

将self手动转化为__block类型,这样即可使block不在retain self

0 0