From: Markus Fischer <markus@...>
Date: 2009-05-27T18:10:10+09:00
Subject: Re: String representing relative file name, adding (meta) data?

Again, for my own record:

There were actually still problems with the prior approach: my test was 
flawed as I did not test adding two MyStr classes with the same string 
value. It didn't work.

Thanks to the great and friendly guys over at IRC I was able to craft 
this solution: use a clean custom class, but implement custom hash, eql? 
and <=> method so it works they way I need it within the Set (which 
internally uses Hash) and allows sorting, too.

class Resourcename
     attr_accessor :source_file
     def initialize(name, source_file = nil)
         @name = name.to_s
         @source_file = source_file
     end
     def to_s
         @name
     end
     def hash
         @name.hash
     end
     def eql? other
         @name.eql? other.instance_eval { @name }
     end
     def <=> other
         @name.<=> other.instance_eval { @name }
     end
end

The downsize is, of course, it's not a string. So whenever I need a 
string operation, I need to explicitly call .to_s, but I can live with 
that. Would be nice if it could automatically work in string context, 
like concatentation, too.

- Markus