From: Tim Becker <a2800276@...>
Date: 2007-03-14T20:25:38+09:00
Subject: Re: A simple question regarding ruby method argument

> Can anyone point me how to pass
> argument to method by reference? I mean that the methods/function able
> to change the value of the argument.

Values are always passed by reference:

irb(main):011:0> class Test
irb(main):012:1> attr_accessor :a
irb(main):013:1> end

irb(main):014:0> def modify x
irb(main):015:1> x.a="hello"
irb(main):016:1> end

irb(main):017:0> t = Test.new
irb(main):018:0> t.a="there"

irb(main):019:0> modify t
irb(main):020:0> t.a
=> "hello"


what doesn't work is passing in a parameter `x`, assigning a new value
to x within a function and expecting that assignment to be
'transfered' outside the function scope:

  def modify x
     x=2 # this doesn't work, because it modifies the reference and not
             # the referenced value
  end

  tmp=1
  modify tmp # doesn't work as you'd like, tmp is still 1
  puts tmp
  => 1


If you're familiar with Java, it's more or less the same behaviour.
   -Tim