Xcode上未声明的标识符__bridge

问题描述

我正在尝试将CFUUIDRef转换为NSString *.

I am trying to convert a CFUUIDRef to a NSString *.

之前，我使用以下代码，并且工作正常.

Before, I used the following code, and worked fine.

CFStringRef str = CFUUIDCreateString(NULL, _uuid); # _uuid is of type CFUUIDRef
return (__bridge NSString *) str;

但是，在最近更新了Xcode(或其他我没有注意到的东西)之后，上面的代码给了我错误:

However, after a recent update on Xcode (or other thing that I didn't notice?), the above code gives me the error:

使用未声明的标识符'__bridge'

那么我做错了什么吗?我该怎么解决?

So have I did something wrong? How could I solve it?

===更新===

完整代码:

+ (NSString *)uuidToString:(CFUUIDRef)_uuid {
  CFStringRef str = CFUUIDCreateString(NULL, _uuid); # _uuid is of type CFUUIDRef
  return (__bridge NSString *) str;
}

uuid由以下方式生成:

The uuid is generated by:

uuid = CFUUIDCreate(NULL);

推荐答案

__bridge仅在启用ARC(自动引用计数)的情况下定义.它用于将对象移入和移出ARC控制". (源)

__bridge is only defined with ARC (Automatic Reference Counting) enabled. It is used to "transfer objects in and out of ARC control". (Source)

要打开ARC，请转到您的构建设置，然后将Objective-C Automatic Reference Counting设置为Yes.

To turn on ARC, go to your build settings and set Objective-C Automatic Reference Counting to Yes.

或者，如果您不想使用ARC，只需删除__bridge，它就可以正常工作.

Or, if you do not want to use ARC, simply remove __bridge and it should work fine.

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