Capturing self strongly in this block is likely to lead to retain cycle

Capturing self strongly in this block is likely to lead to retain cycle

block 是代码块的意思。
甲里引用乙，乙里引用甲，就会导致 “retain cycle” -- “形成怪圈”的错误。
网上资料：
解决的办法是 创建一个本地变量 指向 自己(self).
例如：_items 实际上是 self->items,
_block 对象在创建的时候会被retain一次
改成：
__block ViewController *blockSelf = self;
_block = ^{
[blockSelf->_items addObject:@"Hello!"];
};
就可以了。
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DoSomethingManager *manager = [[DoSomethingManager alloc] init];

manager.complete = ^{

//...complete actions

[manager otherAction];

manager.complete = nil; // Objective-C 用这种方法破坏怪圈。

[manager release];

};
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