为什么我必须调用super -dealloc最后，而不是第一？ [英] Why do I have to call super -dealloc last, and not first?

问题描述

正确的例子：

- (void)dealloc {
    [viewController release];
    [window release];
    [super dealloc];
}

错误示例：

- (void)dealloc {
    [super dealloc];
    [viewController release];
    [window release];
}

Althoug在所有其他情况下覆盖一个方法我会先调用super方法实现，在这种情况下，apple总是调用[super dealloc]。为什么？

Althoug in alsmost all other cases when overriding a method I would first call the super's method implementation, in this case apple always calls [super dealloc] in the end. Why?

推荐答案

它只是一个指南。您可以在 [super dealloc] 后调用其他指令。但是你不能访问超类的变量，因为当你调用 [super dealloc] 时它们被释放。调用最后一行中的超类总是安全的。

Its just a guideline. You can call other instructions after [super dealloc]. however you can not access variables of the superclass anymore because they are released when you call [super dealloc]. It is always safe to call the superclass in the last line.

此外，KVO和依赖（触发）键如果依赖于已发布的成员变量，则可能产生副作用。

Also KVO and depended (triggered) keys can produce side effects if they are depended of already released member variables.

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