为什么Cocoa-Touch类的ivars具有前导下划线字符？ [英] Why do Cocoa-Touch class ivars have leading underscore character?

问题描述

这个约定有什么目的吗？

Is there some purpose for this convention?

推荐答案

Apple喜欢使用下划线来表示 Cocoa的编码指南：

Apple likes to use underscores to mean "private", according to the Coding Guidelines for Cocoa:

避免使用下划线字符作为前缀，方法。苹果保留使用这个约定。第三方使用可能导致命名空间冲突;他们可能会不小心使用自己的方法覆盖现有的私有方法，造成灾难性的后果。

Avoid the use of the underscore character as a prefix meaning private, especially in methods. Apple reserves the use of this convention. Use by third parties could result in name-space collisions; they might unwittingly override an existing private method with one of their own, with disastrous consequences.

以下划线开头的方法名称 Objective-C编程语言（这意味着即使你不使用Cocoa也可以保留它们）：

Method names beginning with underscores are reserved according to The Objective-C Programming Language (which means they're reserved even if you don't use Cocoa, presumably):

以_开头的方法名称，单个下划线字符保留供Apple使用。

Method names beginning with "_", a single underscore character, are reserved for use by Apple.

C / C ++约定是（通常）保留用于实现的前导下划线。很多人误解了这一点，并使用_任何私人;导致_FooLog（）调用在我们的代码库的一个大块中的扩散，即使它调用未定义的行为。

Additionally, the C/C++ convention is that leading underscores are (often) reserved for the implementation. A lot of people misinterpret this and use _ for anything "private"; leading to the proliferation of _FooLog() calls in a large chunk of our codebase, even though it invokes undefined behaviour.

这么做的唯一原因是阻止直接ivar访问在您自己的类。使用 @private 阻止其他类的ivar访问。

The only reason to do it is to discourage direct ivar access in your own class. Prevent ivar access from other classes with @private.

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