From: Alan Chen <alan@...>
Date: 2002-06-07T05:38:20+09:00
Subject: Re: Returning an instance from a different class from new

On Fri, Jun 07, 2002 at 04:53:23AM +0900, Jos Backus wrote:
> [For some reason I am no longer subscribed to ruby-talk and I don't get any
> mail back from the ctl address, which is why I have to use my provider's
> crappy newsserver :-(]
> 
> How do I make the following return Bar instead of Foo?
> 
> class Foo
>   def initialize(sel)
>     case sel
>       when "1"
>         return Bar.new
>       when "2"
>         return Baz.new
>     end
>   end
> end
> 
> class Bar < Foo
>   def initialize
>     self
>   end
> end
> 
> class Baz < Foo
>   def initialize
>     self
>   end
> end
> 
> o = Foo.new("1")
> p o.type
> 
> Thanks,
> Jos

I would recommend breaking out the functionality in
Foo's initialize into a factory function.

module FooFactory
  def build(sel)
    case sel
    when "1"
      return Bar.new
    when "2"
      return Baz.new
    end
  end

  class Foo
# ...
  end

  class Bar < Foo
# ...
  end
end

o = FooFactory.build('1')
p o.type

-- 
Alan Chen
Digikata LLC
http://digikata.com