PartiallyImplementedInterface mixin

partially_implemented_interface.rb

module PartiallyImplementedInterface
  def self.not_implemented_error(klass, method)
    raise NotImplementedError, not_implemented_message(klass, method), caller(2)
  end

  def self.not_implemented_message(klass, method_name)
    "#{method_name} must be implemented by subclasses of #{klass.name}!"
  end
  private_class_method :not_implemented_message

  def not_implemented(*methods)
    methods.each do |iface_method|
      define_method(iface_method) do
        PartiallyImplementedInterface.not_implemented_error(self.class, iface_method)
      end
    end
  end
end

class Meow
  extend PartiallyImplementedInterface

  not_implemented :nesting

  def lots_of_nesting; lots; end
  def lots; of; end
  def of; nesting; end
end

Meow.new.lots_of_nesting
# example.rb:27:in `of': nesting must be implemented by subclasses of Meow! (NotImplementedError)
#        from example.rb:26:in `lots'
#        from example.rb:25:in `lots_of_nesting'
#        from example.rb:30:in `<main>'