在Objective-C中#define后的冒号 [英] Colon after #define in Objective-C

问题描述

在Objective-C中，您可以使用#define

In Objective-C you can define macros using the #define

#define kSomeMacro 1024

然后使用该宏执行类似的操作...

and then use that macro for something like this...

if (kSomeMacro == 1024) {
   ....
}

但是，如果您定义的宏末尾带有冒号

However if you define your macro with a colon on the end

#define kSomeMacro 1024;

然后，if语句将不起作用.这背后的原因是什么?为什么在定义宏时放一个;，编译器为什么不抱怨?

Then the if statement won't work. What is the reasoning behind this and why doesn't the complier complain if you put a ; when defining the macro?

推荐答案

宏仅被其定义替换.当您#define k 1024;并编写if(k==1024)...时，编译器实际看到的是:

Macros are just replaced by their definition. When you #define k 1024; and write if(k==1024)... what the compiler actually sees is:

if(1024; == 1024) ...

无法编译.

编译器不会抱怨，因为有时您实际上可能想在宏中添加分号(;称为分号，而不是冒号，即:).

The compiler doesn't complain because sometimes you may actually want to add a semicolon (; is called semicolon, not colon, which is :) to your macro.

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