Objective-C设置nil和释放之间的差异 [英] Objective-C Difference between setting nil and releasing

问题描述

我知道在 dealloc 中你可以 [object release]; > viewDidUnload （在UIViewController子类中） self.object = nil 。真正的区别是因为 self.object = nil （我们假设对象是（nonatomic，retain）属性）保留 nil （不做任何操作），然后释放旧值，然后引用计数为0对吧？

I've learned that in dealloc you do [object release]; but in viewDidUnload (in a UIViewController subclass) you do self.object = nil. What is really the difference because self.object = nil (we're assuming object is a (nonatomic, retain) property) retains nil (which does nothing) and then releases the old value and then the reference count is 0 right?

推荐答案

self.object = nil 调用您的setter，将释放旧值，将成员设置为 nil ，可能做其他事情（这是一个方法，所以它可以做任何事情）。 任何东西部分是潜在的危险;请参阅此问题，例如

self.object = nil calls your setter, which will release the old value, set the member to nil, and possibly do other things (it's a method, so it could do anything). The "anything" part of that is potentially dangerous; see this question, for example.

[object release] 释放旧值，但将成员保留为现在悬停指针，这是一个很好的食谱的bug。在 dealloc 它没有什么关系，因为指针本身即将消失，但在任何其他情况下，释放一个成员没有设置它是一个非常糟糕的主意到 nil 。

[object release] releases the old value, but leaves the member as a now-dangling pointer, which is a good recipe for bugs. In dealloc it doesn't really matter, since the pointer itself is about to go away too, but in any other case it's a very bad idea to release a member without setting it to nil.

（作为一个旁注，你不应该假设释放一个对象给它一个引用计数0.它释放你的引用，但其他对象可能仍然引用它。）

(As a sidenote, you should never assume that releasing an object gives it a reference count of 0. It releases your reference, but other objects may still have references to it.)

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