具有+的Objective-C类名称 [英] Objective-C class names with a +

问题描述

一个类名，例如UIImage+Something或UIImageView+Somethingelse，是否意味着它像自定义的UIImage或UIImageView一样起作用?

Does a class name, say UIImage+Something or UIImageView+Somethingelse, mean that it acts like a custom UIImage or UIImageView?

推荐答案

我认为您正在查看的是类别"而不是类"的文件名.在类名称或Objective-C中的任何其他标识符中，不允许使用加号+.

I think you are looking at the file names of Categories, not Classes. The plus character + is not allowed in class names or any other identifier in Objective-C.

Objective-C类别是一种将方法(但不包括实例变量)添加到您不一定有其来源的类的方法.例如，如果您经常要制作UIImage的上下副本，则可以使用类别将upsideDownImage方法添加到UIImage类上.

An Objective-C category is a way of adding methods (but not instance variables) to a class you don't necessarily have the source to. For example, if you frequently want to make upside-down copies of UIImages, you can use a category to add a upsideDownImage method onto the UIImage class.

通常将此代码保存在名为UIImage+UpsideDown.m的文件中(带有随附的头文件UIImage+UpsideDown.h).

It's common to save this code in a file named UIImage+UpsideDown.m (with an accompanying header file, UIImage+UpsideDown.h).

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