From: Robert Gleeson <rob@...>
Date: 2009-11-01T01:44:15+09:00
Subject: Re: In-place parameter modification

Hello,

Dave Anderson wrote:
> Native to ruby are several methods that change passed-in parameters
> in-place, such as chomp!(somestring). But I don't see any info on
> creating these things myself. Is it possible to write methods that
> change parameters this way?

Yup, you can write your own mutating methods that mutate the 
receiver(like chomp!, gsub!, sub!, and so on), but you can't mutate any 
of the core classes because you cannot reassign self.

If it were your own class, though, you might have:

class MyString

  def initialize str
    @str = str
  end

  def append!
    @str << ' ruby'
  end

  def to_s
    @str
  end

end

str = MyString.new 'I love '
str.append!
puts str # => 'I love ruby'

chomp! takes one argument, and that is a seperator(or what to remove 
from the end of the string)

Hope this helps some,
Rob
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