RELEASE_SAFELY 是什么意思，为什么它在 xcode4 中不起作用? [英] What does RELEASE_SAFELY mean and why does it not work in xcode4?

问题描述

RELEASE_SAFELY 或 RELEASE_CF_SAFELY 是什么意思?好吧，它是为了释放对象，但为什么不使用 [obj release] ?

what does RELEASE_SAFELY or RELEASE_CF_SAFELY mean? Ok, it's for releasing objects but why not use [obj release]?

此外，我尝试在 xcode 4 中使用它，但遇到了错误:

Besides I tried to use it in xcode 4 but I am running into buid errors:

Undefined symbols for architecture i386:
  "_RELEASE_SAFELY", referenced from:
      -[AdressBookModel search:] in AdressBookModel.o
ld: symbol(s) not found for architecture i386
collect2: ld returned 1 exit status

我可以只做 [obj release] 吗?你会考虑什么?

Can I do just [obj release] instead? What would you consider?

推荐答案

RELEASE_SAFELY 不是函数而是宏，通常是这样定义的:

RELEASE_SAFELY is not a function but a macro and is usually defined like this:

#define RELEASE_SAFELY(__POINTER) { [__POINTER release]; __POINTER = nil; }

(我认为它不是 SDK 的一部分，而是必须在每个项目中单独声明.我认为它与 XCode 版本没有任何关系.)

(I think it's not part of the SDK but has to be declared in each project separately. And I don't think it has anything to do with the XCode version.)

所以它首先调用release，然后另外将变量设置为nil.这是一种很好的做法，因为它可以防止重复释放或访问已释放的实例.

So it first calls release and then additionally sets the variable to nil. That's good practice because it prevents double releases or access to a deallocated instance.

您的代码似乎认为它是一个函数(而不是宏).可能编译器会警告您它尚未声明.

It seems that your code believes it's a function (instead of a macro). Probably the compiler warns you that it hasn't been declared.

解决方法是将上述宏定义放在适当的头文件中.

The fix is to put the above macro definition in an appropriate header file.

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