From: James Edward Gray II <james@...>
Date: 2006-12-03T08:39:12+09:00
Subject: Re: Factory pattern, abstract base class

On Dec 2, 2006, at 5:15 PM, Daniel Berger wrote:

> Perhaps my whole approach is wrong.  What is the proper way to achieve
> what I'm after (without resorting to making Bar a module)?

This works, but is probably poor style:

module Foo
   class Bar
     def initialize(arg)

     end

     class << self
       alias_method :__new__, :new
       def new(arg)
         return if self != Foo::Bar
         case arg.downcase
         when 'baz'
           return Baz.__new__(arg)
         when 'zap'
           return Zap.__new__(arg)
         end
       end
     end
   end

   class Baz < Bar; end
   class Zap < Bar; end
end

fb = Foo::Bar.new('baz')  # => #<Foo::Baz:0x1e2c0c>

__END__

I prefer somthing like this though:

module Foo
   class Bar
     def self.factory(arg)
       return if self != Foo::Bar
       Foo.const_get(arg.capitalize).new(arg)
     end

     def initialize(arg)

     end
   end

   class Baz < Bar; end
   class Zap < Bar; end
end

fb = Foo::Bar.factory('baz')  # => #<Foo::Baz:0x1e2f2c>

__END__

Hope that helps.

James Edward Gray II