From: Joel VanderWerf <vjoel@...>
Date: 2005-01-09T03:28:49+09:00
Subject: Re: Seeking info on keyword parameters

Stefan Lang wrote:

> That reminds me a bit of C# attributes. Attributes are
> available to reflection and can be attached to methods, classes
> and other type definitions.
> 
> So one can write:
> [ConditionalAttribute("DEBUG")]
> void debug_method(string msg)
> {
> ....
> }
> 
> to tell the compiler, development tools and other
> developers that this method is intended for debugging.
> (One effect of the example above is, that the C# compiler
> compiles the method only if the DEBUG symbol is set.)
> 
> New attributes can be defined like classes, so you
> can attach any meta data you like to classes, methods etc.
> 
> I think this could be useful for Ruby too.
> 

Could be done...

$meta = {}

def meta_set(tag, obj=self)
   case obj
   when Symbol # designates a method
     $meta[instance_method(obj)] = tag
   when Module
     $meta[obj] = tag
   else
     # ...
   end
end

module M
   meta_set("a module")
   class C
     meta_set("a class")
     def foo; end
     meta_set("a method", :foo)
   end
end

p $meta

__END__

Output:

{M=>"a module", #<UnboundMethod: M::C#foo>=>"a method", M::C=>"a class"}