Parametric modules in Ruby

gistfile1.rb

class Printable < Module
  def initialize(string)
    super()
    define_method :print do
      puts string
    end
  end
end

>> class A; include Printable.new('Hello'); end
>> class B; include Printable.new('Goodbye'); end

>> A.new.print
Hello

>> B.new.print
Goodbye

---

# @tomafro suggested something better:

module TimeoutThing
  def do_something
    puts timeout
  end

  def self.with(options = {})
    Module.new do |m|
      include TimeoutThing
      options.each do |k, v|
        define_method k do
          v
        end
      end
    end
  end
end

TimeoutThing.with(:timeout => 20)

class A
  include TimeoutThing.with(:timeout => 20)
end

class B
  include TimeoutThing.with(:timeout => 40)
end

A.new.do_something
B.new.do_something

---

# I think I like this best:

module Parametric
  def with(options)
    base = self
    Module.new do
      include base
      options.each do |k, v|
        define_method(k) { v }
      end
    end
  end
end

module Printable
  extend Parametric

  def print
    puts string
  end
end

>> class A; include Printable.with(:string => 'Hello'); end
>> class B; include Printable.with(:string => 'Goodbye'); end

>> A.new.print
Hello

>> B.new.print
Goodbye

I didn't realise that a module which contained an initialize method would gain a corresponding new - interesting. Regardless, I think any solution is going to have the same key characteristics that both yours and @tomafro's has - the creation of a new Module, with method(s) defined using define_method to get closure-like behaviour to bind the 'class'-level argument to the instance method implementation.

To clarify: it's not a module, it's a class which subclasses Module and therefore produces a module when instantiated. Mmm, contrived.

I like @tomafro's solution because it gives you a nice place to put (static) method definitions. I'll probably go with slightly less magic, i.e. define_method :options { options } rather than options.each do … end, but otherwise it's what I'm going to use for now. I think you're right that there's no beautiful way. Maybe I'll put the definition of #with in its own module and use it to extend any modules that I want to make parametric?