From: Trans <transfire@...>
Date: 2005-10-31T12:12:07+09:00
Subject: Re: C# attributes in Ruby?


zdennis wrote:
> Stephan Mueller wrote:
> > Hi,
> >
> > sorry if this has been discussed before (in this case please point me in
> > the right direction :). I am wondering if there is a mechanism in Ruby to
> > get something as C# does with its attributes. In C# attributes are a way
> > to tag namespaces, classes, methods etc. with metadata which can be quite
> > usefull in combination with reflection.
> >
> > exmpl:
> >
> >  ...
> >  [SomeFancyAttribute(EvenMoreFancyValue)]
> >  public int GetValue()
> >  {
> >   ...
> >  }
> >
> > This would associate the attribute SomeFancyAttribute with its value
> > EvenMoreFancyValue with (to?) the method GetValue. Later this information
> > could be retrieved via reflection and used for whatsoever.
> >
> > Is there a way to achieve something comparable with ruby?
> >
> >
> > Thanks for your thoughts!
>
> Steph,
>
> I am trying to see where you would use? Is the below example valid of how-you would use it?
>
> arr = [ obj1, obj2, obj3, obj4 ]
> arr.each do |x|
>     puts obj1.value if obj1.ann.fancy_attribute =~ /fancy_value/
> end
>
> OR
>
> fancy_objects = 0
> ObjectSpace.each_object{ |obj| fancy_objects += 1 if obj.ann.fancy_attribute =~ /fancy_value }
> puts "YOu had #{fancy_object} fancy objects"
>

Yes. That's about right. Keep in mind though that #ann works
differently for classes and modules than it does for other objects b/c
it is used for method annotations in those cases. So use #annotation
instead in this last example. I may change #ann for objects to reflect
the same functionality so there won't be any possible confusio. I
suppose obj#ann could apply to singleton methods --but I'm not sure
yet.

T.