objective-c - 嵌套块和对自身的引用

Question

我有一个我使用的块，self所以我声明了一个对 self 的弱引用：

__weak MyClass *weakSelf = self;

现在我的问题：

1. 我在定义的地方出现错误，我weakSelf不明白这应该是什么意思。：

   无法在自动变量上指定弱属性

2. 在我的街区内，我传递weakSelf到另一个街区，我不确定我现在是否必须像这样再次做同样的事情：

   __weak MyClass *weakWeakSelf = weakSelf;
   

   然后传到weakWeakSelf那个街区？

Answer 1

这很可能发生在您针对 iOS 4 时。您应该将其更改为

__unsafe_unretained MyClass *weakWeakSelf = weakSelf;

Answer 2

带弧

__weak __typeof__(self) wself = self;

没有ARC

__unsafe_unretained __typeof__(self) wself = self;

Answer 3

使用libextobjc，它将易于阅读且易于阅读：

- (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];

        }];
    }];
}