嵌套块和引用自我

我有一个块，我使用self所以我宣布对自我的一个弱引用：

 __weak MyClass *weakSelf = self; 

现在我的问题：

1. 我在定义weakSelf遇到一个错误，我不明白这应该是什么意思。

   无法在自动variables上指定弱属性

2. 在我的街区里面，我将weakSelf传递给另一个街区，我不知道现在是否必须再次做同样的事情：

    __weak MyClass *weakWeakSelf = weakSelf; 

   然后把weakWeakSelf传给那个块？

Answer 1

这是最有可能发生，因为你是针对iOS 4。你应该改变它

 __unsafe_unretained MyClass *weakWeakSelf = weakSelf; 

Answer 2

用ARC

 __weak __typeof__(self) wself = self; 

没有弧

 __unsafe_unretained __typeof__(self) wself = self; 

Answer 3

使用libextobjc它将是可读和容易的：

 - (void)doStuff { @weakify(self); // __weak __typeof__(self) self_weak_ = self; [self doSomeAsyncStuff:^{ @strongify(self); // __strong __typeof__(self) self = self_weak_; // now you don't run the risk of self being deallocated // whilst doing stuff inside this block // But there's a chance that self was already deallocated, so // you could want to check if self == nil [self doSomeAwesomeStuff]; [self doSomeOtherAsyncStuff:^{ @strongify(self); // __strong __typeof__(self) self = self_weak_; // now you don't run the risk of self being deallocated // whilst doing stuff inside this block // Again, there's a chance that self was already deallocated, so // you could want to check if self == nil [self doSomeAwesomeStuff]; }]; }]; }