为什么一些Objective-C文件名的名称中有减号或加号 [英] Why do some Objective-C file names have a minus or plus sign in their name

问题描述

在我要添加到我的项目的库中，有一个名为NSString-Base64Extensions.h（带有NSString-Base64Extensions.m）和一个叫NSString + PECrypt.h（带有NSString + PECrypt.m）的文件。 / p>

这是什么意思？

解决方案

文件，其中包含现有类的类别。

你可以期望NSString + PECrypt.m包含一个类别，它添加到 NSString 的方法。同样，NSString-Base64Extensions是 NSString 上的类别方法。

类别是一种将方法添加到现有类在Objective-C中，没有子类化，将在此处中详细讨论。

In a library I want to add to my project, there is a file called NSString-Base64Extensions.h (with NSString-Base64Extensions.m) and one called NSString+PECrypt.h (with NSString+PECrypt.m).

What does this signify?

解决方案

That is the convention for naming files, that contain categories for existing classes. The - and + sign are just different ways of expressing that, no difference other than style.

You can expect NSString+PECrypt.m to contain a Category that adds to the methods of NSString. Likewise, NSString-Base64Extensions are Category methods on NSString.

Categories are a way of adding methods to an existing class in Objective-C, without subclassing, it is discussed in more detail here.

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