宏还可以生成方法名称吗? [英] Can a macro also generate a method name?

问题描述

使用宏来创建方法名通常是否有效?我的意思是……实际上，这只是在编译器实际运行之前进行简单的文本替换，对吗?

Is it generally valid that a macro is used to create a method name? I mean...actually it's just simple text replacement before the compiler actually runs, right?

推荐答案

是的，它是有效的；宏扩展发生在编译器甚至没有读取代码之前.主要限制是不能将预处理器指令嵌入到预处理器指令中.因此，例如:

Yes, it is valid; macro expansion occurs before the compiler even reads the code. The main limitation is that one cannot embed a preprocessor directive within a preprocessor directive. So, for example:

// This is ok:
#define PREFIX(X) this_name_is_prefixed_ ## X
// ...
- (void) PREFIX(doSomething):id;
// ...

// But this isn't:
#define IMPORT(X) #import X
IMPORT(<Foundation/Foundation.h>) // <= Don't expect this to work

除"#import"指令外，Objective-C的预处理器基本上与 C预处理器. ("#import"类似于"#include"，除了#import意味着仅包含一次，因此仅包含在#import中的标头不需要预处理器保护).

With the exception of the "#import" directive, Objective-C's preprocessor is basically the same as the C preprocessor. (The "#import" is like "#include", except that #import implies include only once, so preprocessor guards are not required for headers that are included only with #import).

这篇关于宏还可以生成方法名称吗?的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！