Objective C - 为什么常量以 k 开头

Objective C - Why do constants start with k(Objective C - 为什么常量以 k 开头)

问题描述

为什么我见过的所有例子中的常量总是以 k 开头?我应该在头文件或 .m 文件中#define 常量吗?

Why do constants in all examples I've seen always start with k? And should I #define constants in header or .m file?

我是 Objective C 的新手，我不知道 C.是否有一些教程可以在不假设 C 知识的情况下解释这些事情?

I'm new to Objective C, and I don't know C. Is there some tutorial somewhere that explains these sorts of things without assuming knowledge of C?

推荐答案

以k"开头的常量是 Mac OS X 之前的遗留问题.事实上，我认为这种做法甚至可能来自当时的方式，当时 Mac OS 主要是用 Pascal 编写的，主要的开发语言是 Pascal.在 C 中，#define 的常量通常以全大写形式编写，而不是以k"为前缀.

Starting constants with a "k" is a legacy of the pre-Mac OS X days. In fact, I think the practice might even come from way back in the day, when the Mac OS was written mostly in Pascal, and the predominant development language was Pascal. In C, #define'd constants are typically written in ALL CAPS, rather than prefixing with a "k".

至于在哪里#define 常量:#define 它们你将在哪里使用它们.如果您希望 #import 您的代码的人使用这些常量，请将它们放在头文件中；如果常量只在内部使用，请将它们放在 .m 文件中.

As for where to #define constants: #define them where you're going to use them. If you expect people who #import your code to use the constants, put them in the header file; if the constants are only going to be used internally, put them in the .m file.

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