如何使用va_args传递参数(可变参数，省略号) [英] How to use va_args to pass arguments on (variadic parameters, ellipsis)

问题描述

我无法理解Objective-C中多个参数的语法.我已经看到了这个问题，但是答案还没有帮助我(至今).

I can't get my head around the syntax for multiple arguments in Objective-C. I have seen this question, but the answer hasn't helped me (yet).

这是我的代码(实际上，我最终希望将其传递给NSString stringWithFormat，但是使NSLog正常工作就足够了):

Here is my code (actually I will want to eventually pass to NSString stringWithFormat, but getting an NSLog to work would be good enough for now):

- (void)applicationDidFinishLaunching:(NSNotification *)aNotification {
     // Insert code here to initialize your application 
     [self log:@"blah blah %d", 32];
}


- (void)log:(NSString *)text, ... {
      va_list args;
      va_start(args, text);
      NSLog(text, args);
}

参数(或某些参数)通过，但是它有一些奇怪的值(输出为blah blah 1606412704).我应该如何传递通过...输入的值?

The argument (or some argument) comes through, but it's got some weird value (output is blah blah 1606412704). How should I pass the values that come in via ...?

推荐答案

有NSLog的一种变体，它接受名为

There's a variant of NSLog that accepts a va_list called NSLogv:

- (void) log:(NSString *)text, ... {
  va_list args;
  va_start(args, text);
  NSLogv(text, args);
  va_end(args);
}

转发实际的...(不是va_list)的唯一方法是使用宏.例如:

The only way to forward the actual ... (not the va_list) is to use a macro. For example:

#define MyLog(f, ...) { \
NSLog(f, ##__VA_ARGS__); \
[someObject doSomething:f, ##__VA_ARGS__]; \
}

但是，应该非常谨慎地使用它，因为宏会使代码确实变得模糊不清.

However, this should be used very sparingly, since macros can make code really obfuscated.

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