NullObject

null.rb

class NullObject
  def initialize target_class
    @target_class = target_class
  end
  def method_missing method, *args, &block
    if @target_class.instance_methods.include?(method)
      nil
    else
      raise "Tried to call '#{method}' on a NullObject for #{@target_class}; method doesn't exist on #{@target_class}"
    end
  end
end
module HasNullObject
  def null_object
    @@null_object
  end
  def define_null_object &block
    @@null_object = NullObject.new(self)
    eigen = class << @@null_object; self; end
    eigen.class_eval &block
  end
end
class Partner
  def domain
    "http://c2.com/cgi/wiki"
  end
  def payment_method
  end
  
  # here we override our methods that should behave differently from returning nil
  extend HasNullObject
  define_null_object do
    def domain
      "http://land_of_the_nulls.com"
    end
  end
end

missing_partner = Partner.null_object

puts missing_partner.payment_method
puts missing_partner.domain
puts missing_partner.domin