From: Robert Klemme <shortcutter@...>
Date: 2006-08-08T17:25:10+09:00
Subject: Re: How to make objects that can set $1 when obj =~ /(.)/ is called ?

Tomasz Wegrzanowski wrote:
> Something like that would be a reasonable thing to do:
> 
> class Foo
>  def initialize(t)
>    @text = t
>  end
>  def =~(x)
>    @text =~ x
>  end
> end
> 
> And it works for non-capturing regexps,
> but when we want to capture something
> $1 etc. are bound only within the =~ method,
> and when the method returns they are
> restored to their previous values.
> 
> Foo.new("Hello") =~ /(e)/ # => 1
> $1 # => nil
> 
> Is it possible to somehow get =~ like that work,
> even if it takes heavy metaprogramming hackery ?

The simplest solution might be to use #match:

class Foo
  def initialize(t)
    @text = t
  end
  def =~(x)
    x.match @text
  end
end

 >> md = Foo.new("Hello") =~ /(e)l/
=> #<MatchData:0x3a40c0>
 >> md.to_a
=> ["el", "e"]

You can do more of course, like storing MatchData along with your Foo 
instance etc.  What problem are you trying to solve?

Kind regards

	robert