module ModelFactory

  def valid_user_attributes
    {
      :username => "scott",
      :password => "my-pass",
      :password_confirmation => "my-pass",
      :gender => "male",
      :email_address => "scott@railsnewbie.com",
      :email_address_confirmation => "scott@railsnewbie.com",
      :date_of_birth => Time.mktime('1985', '06', '12'),
      :active => true
    }
  end

  def valid_comments
    {
      :text => "blah blah",
      :post => create_post
    }
  end

  # ...
end


## implementation:



module ModelFactory; end

ModelFactory.module_eval do

  instance_methods.each do |method|
    if method =~ /valid_(.*)_attributes/
      model_name_as_underscores = $1
      model_name_as_class = instance_eval($1.classify)

      define_method "new_#{model_name_as_underscores}" do |*args|
        hash = create_hash_from_args(*args)
        model_name_as_class.new(instance_eval("#{method}.merge(hash)"))
      end

      define_method "create_#{model_name_as_underscores}" do |*args|
        hash = create_hash_from_args(*args)
        obj = instance_eval "new_#{model_name_as_underscores}(hash)"
        obj.save!
        obj
      end
    end
  end

private

  def create_hash_from_args(*args)
    hash = *args
    hash ||= Hash.new
  end
end