目标c中的ARC循环引用使用委托 [英] ARC circular reference in objective-c uses delegate

问题描述

您好！

我试图在我的应用程序中使用委托。我的项目使用 ARC

I tried to use a delegate in my app. My project uses ARC

例如，我有协议X​​和两个使用它的对象。
在对象 B 中，我创建了一个对象 A 的实例，并设置委托自身（A.delegate = self）
在运行时，我调用一个方法callBack （在这一点上，我的委托对象是 B ）。之后，他们都执行 -showResult 方法。

For example, I have protocol X and two object which uses it. In object B I created an instance for object A and set delegate self (A.delegate = self) In runtime I invoke a method callBack (in this point my delegate object is B). After that they all execute the -showResult method.

在什么点创建循环引用？我明白这是说明者 strong 的问题，但我不明白发生了什么时间，以及如何追踪。

At what point is a circular reference formed? I understand that this is a problem with the specifier strong, but I don't understand what time it happened, and how to track it.

谢谢！

推荐答案

如果两个对象都保持强烈的引用（即彼此保持一致），则可以在你手上有所谓的保留周期。两个对象都不会被释放，因为另一个对象有很强的引用（保留它），所以它永远不会放弃其引用（释放）另一个对象。

If two objects both maintain strong references to each other (that is, they retain each other), you may have what's known as a 'retain cycle' on your hands. Neither object will ever be deallocated because the other has a strong reference to it (retains it), and so it will never give up its reference (release) the other object.

这种情况与代表很常见，其中一个对象（称为A）创建另一个对象（B）并将其设置为B的委托。如果A对B有很强的引用，所以B不会被释放，而B也有很强的参考A，你有一个参考周期。为了避免这种情况，对于不保留或强烈引用其代表的对象来说，这是常见的。让B参考一个弱而不是强者，问题就会消失。

This situation is common with delegates, where one object (call it A) creates another (B) and sets itself as B's delegate. If A has a strong reference to B so that B won't get deallocated, and B also has a strong reference to A, you have a reference cycle. In order to avoid that, it's common for objects not to retain or keep strong references to their delegates. Make B's reference to A weak instead of strong and the problem goes away.

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