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Re: Macro challenge with variable arguments
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Re: Macro challenge with variable arguments


  • Subject: Re: Macro challenge with variable arguments
  • From: Greg Parker <email@hidden>
  • Date: Thu, 01 Nov 2012 19:34:38 -0700

On Nov 1, 2012, at 7:15 PM, Graham Cox <email@hidden> wrote:

> Hi all, I'm having trouble figuring this out.
>
> I have a logging function thus:
>
> 	void	GCLogObjCMethod( id obj, SEL selector, NSUInteger lineNumber, NSString* tag, NSString* format, ... );
>
> I'd like to be able to wrap this using a macro that automatically supplies the object, selector, line number and 'tag' (which is usually the class name of the object) and leaves only the format and the variable arguments to be supplied. I haven't been able to come up with a way that works. Can it be done? i.e. what I want is a macro:
>
> GCLOGOC( @"this is a format string: %@, with any number of params: %@", paramA, paramB );
>
> and this expands to:
>
> GCLogObjCMethod( self, _cmd, __LINE__, NSStringFromClass([self class]), @"this is a format string: %@, with any number of params: %@", paramA, paramB );
>
> (or expands to nothing at all if logging has been turned off).
>
> How can I define the macro so it can handle the variable parameter list?

Look up __VA_ARGS__. I think you can build what you want that way.


--
Greg Parker     email@hidden     Runtime Wrangler



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References: 
 >Macro challenge with variable arguments (From: Graham Cox <email@hidden>)

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