我是否必须手动删除KVO中的Observer [英] Do I have to removeObserver in KVO manually

问题描述

我已经阅读了苹果文档

I have read the apple document about KVO, and it said:

注意:键值遵循addObserver:forKeyPath:options:context: 方法不维护对观察对象的强引用， 观察到的对象或上下文.你应该确保你 保持对观察对象和被观察对象的强烈引用， 以及必要的上下文.

Note: The key-value observing addObserver:forKeyPath:options:context: method does not maintain strong references to the observing object, the observed objects, or the context. You should ensure that you maintain strong references to the observing, and observed, objects, and the context as necessary.

观察者对象没有对观察对象的强引用.

The observer object not have a strong references to the observered object.

这个人我不能在dealloc方法中调用removeObserver:forKeyPath:吗?它可以自动删除观察者吗?

Does this man I can not call removeObserver:forKeyPath: in the dealloc method? Can it remove the observer automatically?

推荐答案

您必须手动调用-removeObserver:forKeyPath:. iOS不会自动执行此操作.

You must call -removeObserver:forKeyPath: manaully. iOS will not do it automatically.

Apple说 does not maintain strong references to the observing object .我认为这意味着，如果要为超出temp var范围的temp var移除RemoveObserver，则应将temp var设为ivar，以便维护ivar的强引用.

Apple said does not maintain strong references to the observing object. I think it means, if you want to removeObserver for a temp var out off the temp var's scope, you should make the temp var as ivar, so you maintain the ivar's strong references.

如果您不拨打-removeObserver:forKeyPath:.您将做出以下操作:1)东西泄漏

If you do not call -removeObserver:forKeyPath:. You will make : 1) Something leak

例如您这样的代码:

[self addObserver:a forKeyPath:@"name" options:NSKeyValueObservingOptionNew context:nil];

(如果您不呼叫-removeObserver:forKeyPath:).它将控制台:

if you do not call -removeObserver:forKeyPath:. It will console that :

An instance 0x756a1d0 of class MyClass was deallocated while key value observers were still registered with it. Observation info was

泄漏，甚至可能错误地附着在其他物体上. 在NSKVODeallocateBreak上设置一个断点以在调试器中停止. 这是当前的观察信息: [NSKeyValueObservationInfo 0x7574f60]( [NSKeyValueObservance 0x7574f20:观察者:0x7568280，键路径:pageCount，选项:[新:是，旧:否，优先:否]上下文:0x0， 属性:0x7574fa0] )

leaked, and may even become mistakenly attached to some other object. Set a breakpoint on NSKVODeallocateBreak to stop here in the debugger. Here's the current observation info: [NSKeyValueObservationInfo 0x7574f60] ( [NSKeyValueObservance 0x7574f20: Observer: 0x7568280, Key path: pageCount, Options: [New: YES, Old: NO, Prior: NO] Context: 0x0, Property: 0x7574fa0] )

调试时，您会发现:self和a没有泄漏.泄漏的是NSKeyValueObservationInfo object

When you debug it, you will find : The self and the a are not leaking. The leaking thing is the NSKeyValueObservationInfo object

如果您不拨打-removeObserver:forKeyPath:.您将获得:2)中级课程永远不会破坏&&无限通知

If you do not call -removeObserver:forKeyPath:. You will make : 2) Intermediate class never destroy && Infinity notification

正如苹果公司有关KVO的文件所述:

As the Apple document about KVO says:

注册观察者以获取对象的属性时，isa 观察对象的指针被修改，指向 中产阶级而不是真正的阶级.

When an observer is registered for an attribute of an object the isa pointer of the observed object is modified, pointing to an intermediate class rather than at the true class.

当您删除Observer时，如果未注册任何观察者，则中间类将销毁.而且，如果不调用removeObserver，则中间类将永远不会销毁，并且当您更改属性时，中间类的setter方法将继续发送通知.

When you removeObserver, if no observer is registered, the intermediate class will destroy. And If you not call removeObserver, the intermediate class will never destroy and when you change the property, the setter method of intermediate class will continue to send notifications.

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