From: Kent Dahl <kentda@...>
Date: 2002-03-30T16:13:55+09:00
Subject: Re: Creating an instance of a class without calling initialize()

Harry Ohlsen wrote:
> 
> For reasons that I'll go into if someone's interested,
> I'd like to be able to create an instance of an arbitrary
> class, without having its initialize() method called.

Please do. Curious minds have been intrigued.

> Is there a way to do that in pure Ruby, or, if not, to
> write a C extension that allows me to do it by interacting
> with the VM somehow?

The naive, "thought-it-up-in-2-shakes-of-a-lambs-tail", evil-eval way:

<CODE>
class Class
  def new_without_init( *args )
    self.class_eval %{
      alias :old_initialize_with_args :initialize
      def initialize( *args );end
    }
    result = self.new( *args )
    self.class_eval %{
      undef :initialize
      alias :initialize :old_initialize_with_args
    }
    result
  end
end


# Testing it...
class A
  def initialize( a, b, c )
      print a, b, c
    @a = a; @b = b; @c = c
  end
  attr_reader :a, :b, :c
end

r1 = A.new_without_init(  1,2,3 )
p r1              #=> #<A:0x401dceb0>
r2 = A.new(1,2,3) #=> 123
p r2              #=> #<A:0x401dcd48  @c=3, @b=2, @a=1>
</CODE>

HTH

-- 
(\[ Kent Dahl ]/)_    _~_    __[ http://www.stud.ntnu.no/~kentda/ ]___/~
 ))\_student_/((  \__d L b__/  NTNU - graduate engineering - 4. year  )
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