From: "Hal E. Fulton" <hal9000@...>
Date: 2002-09-20T09:47:34+09:00
Subject: Thoughts on improving usage of Regexp#match

Please feel free to point out obvious things 
that I'm not seeing here.

I was looking at a piece of code like this:

  sub1 = ""
  if str =~ regex
    sub1 = $1
  end

and I thought three things:
  1. I've never liked the $1 -- I usually avoid 
     Perlish variables, even the common ones.
  2. I don't like the if.
  3. I don't like having to assign sub1 twice.

So I tried writing:

  sub1 = regex.match(str)[1] || ""

In theory this should be the same as the other
four lines of code.

But it doesn't work because if the match
fails, #match returns nil and I can't call
[] on nil.

So I thought: Why don't I make a special
MatchData object that will just return nil 
for any [] call?

<side_note>
Did you know that MatchData doesn't have a 
'new' method?? I had to do a silly hack to 
create a MatchData object before adding a 
singleton method to it.
</side_note>

Here's my code:

  class Regexp
    alias :oldmatch :match
  
    def match(str)
      result = self.oldmatch(str)
      if not result
        null = /x/.match("x") # No new
        def null.[](index); nil; end
        result = null
      end
      result
    end
  end

Thoughts?

Hal