保持ARC的周期 [英] Retain Cycle in ARC

问题描述

我从未从事过非基于ARC的项目.我刚在基于ARC的项目中遇到了一个僵尸.我发现这是因为保留周期.我只是想知道什么是保留周期.可以

I have never worked on non ARC based project. I just came across a zombie on my ARC based project. I found it was because of retain cycle.I am just wondering what is a retain cycle.Can

能给我一个保留周期的例子吗?

Could you give me an example for retain cycle?

推荐答案

当对象A保留对象B，而对象B同时保留对象A时，保留周期是一种情况. > * .这是一个示例:

A retain cycle is a situation when object A retains object B, and object B retains object A at the same time^*. Here is an example:

@class Child;
@interface Parent : NSObject {
    Child *child; // Instance variables are implicitly __strong
}
@end
@interface Child : NSObject {
    Parent *parent;
}
@end

您可以通过为<反向链接>使用__weak变量或weak属性来修复ARC中的保留周期，即指向对象层次结构中直接或间接父级的链接:

You can fix a retain cycle in ARC by using __weak variables or weak properties for your "back links", i.e. links to direct or indirect parents in an object hierarchy:

@class Child;
@interface Parent : NSObject {
    Child *child;
}
@end
@interface Child : NSObject {
    __weak Parent *parent;
}
@end

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^* 这是保留周期的最原始形式；可能有很长的物体将它们彼此围成一圈.

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^* This is the most primitive form of a retain cycle; there may be a long chain of objects that retain each other in a circle.

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