From: Jacob Fugal <lukfugl@...>
Date: 2006-02-03T02:16:11+09:00
Subject: Re: Chomping and stomping

On 2/2/06, John Maclean <info@jayeola.org> wrote:
> #!/usr/bin/ruby -w
> def chomper
>   xx = gets.chomp!
>   until $_ == "qq"
>     puts "hit me with a squirell!"
>     xx = gets.chomp!
>     xx
>   end
> end
>
> chomper
>
> # this works but surely there must be a way to incoporate a variable
> in there?
>
> #!/usr/bin/ruby -w
> def chomper
>   xx = gets.chomp!
>   until xx == "qq"
>     puts "hit me with a squirell!"
>     xx
>   end
> end
>
> #this don't work.

String#chomp! is a "destructive" operation. This means that it acts in
place on its receiver and, in this case, returns nil. So what's
happening here is that Kernel#gets creates a String object, chomp! is
sent to that object, the object is modified in place and nil returned.
That's why xx is nil. As you discovered in your first example, the
String object returned by Kernel#gets is stored in $_. Accessing it
this way isn't a bset practice however.

What you probably want instead is to use the non-destructive twin (the
Good Twin) of String#chomp!, namely String#chomp. Notice the lack of
the bang (!). The bang is generally (but not always) an indicator that
the method is destructive. String#chomp creates a chomped copy of it's
receiver and returns it. Replacing chomp! with chomp it should work:

  #!/usr/bin/ruby -w
  def chomper
    xx = gets.chomp
    until xx == "qq"
      puts "hit me with a squirell!"
      xx
    end
  end

  puts chomper

Jacob Fugal