NSCFString和NSConstantString有什么区别? [英] What is the different between NSCFString and NSConstantString?

问题描述

我将对象变量声明为NSString 但是当我使用XCode来查看对象时，我看到有两种类型的String，看来系统会自动转移到另一种类型:

I declare the object variable as a NSString But when I use the XCode to look into my object, I saw there are two type of String, it seems that the system automatically transfer to another:

它们之间有什么区别?它们可以彼此互换吗?另外，两个条件变为另一个条件是什么?

What are the different between them? Are they interchangeable to one and others. Also, what is the condition two change to another?

谢谢.

推荐答案

它们都是NSString的具体子类. __NSCFString是在运行时通过Foundation或Core Foundation创建的，而__NSCFConstantString是在编译时创建的CFSTR("...")常量或@"..."常量.

They're both concrete subclasses of NSString. __NSCFString is one created during runtime via Foundation or Core Foundation, while __NSCFConstantString is either a CFSTR("...") constant or an @"..." constant, created at compile-time.

它们的接口是私有的.将它们都视为NSString，您应该不会遇到麻烦.

Their interfaces are private. Treat them both as NSString and you should have no trouble.

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