From: Robert Klemme <shortcutter@...>
Date: 2011-04-12T16:00:11+09:00
Subject: Re: Copying parameters to singleton class

On Tue, Apr 12, 2011 at 4:48 AM, 7stud -- <bbxx789_05ss@yahoo.com> wrote:
> ...but then you could do this:
>
> module ClassFactory
>  def ClassFactory.included(includer)
>    includer.extend(ClassMethods)
>  end
>
>  module ClassMethods
>
>    def using(hash)
>      Class.new do
>        @options = hash
>        class << self
>          attr_reader :options
>        end
>      end
>    end
>
>  end
> end
>
> class Opportunities
>  include ClassFactory
> end

I think we can do this simpler if you want to reuse that options
creation functionality:

module ClassFactory
  attr_reader :options

  def using(opts)
    Class.new(self).tap do |cl|
      cl.instance_variable_set '@options', opts.freeze
    end
  end
end

class Opportunities
  extend ClassFactory
end

irb(main):020:0> foo = Opportunities.using(foo: 1, bar: 2)
=> #<Class:0x10952bc0>
irb(main):021:0> foo.options
=> {:foo=>1, :bar=>2}
irb(main):022:0> foo.ancestors
=> [#<Class:0x10952bc0>, Opportunities, Object, Kernel, BasicObject]

> I really wanted to write that like below, but it doesn't work??
>
> module ClassFactory
>  def ClassFactory.included(includer)
>    includer.extend(ClassMethods)
>  end
>
>  module ClassMethods
>
>    def using(hash)
>      Class.new do
>        @options = hash
>      end
>    end
>
>    def options
>      @options
>    end
>
>  end
> end
>
> class Opportunities
>  include ClassFactory
> end
>
> Foo = Opportunities.using({one: 1, two: 2, three: 3})
> Bar = Opportunities.using({four: 4, five: 5, six: 6})
>
> p Foo.options
> p Bar.options
>
> --output:--
> prog.rb:28:in `<main>': undefined method `options' for Foo:Class
> (NoMethodError)

Your new class does not inherit module ClassMethods, that's why.

Kind regards

robert

-- 
remember.guy do |as, often| as.you_can - without end
http://blog.rubybestpractices.com/