my_first_dsl.rb

module Kernel 
  def meta 
    class << self; self; end 
  end 
end 

class Module 
  public :attr_accessor, :attr_reader, :attr_writer 
end

class Spaceship
  
  def self.make(attributes={}, &block)
    return_value = self.new
    return_value.instance_eval(&block)
    return_value
  end
  
  def self.can_have(variable)
    self.attr_accessor variable
  end
  
  def method_missing(id, *args, &block)
    case(id.to_s)
    when /^add_(.*)/
      return unless self.respond_to?("#{$1}s")
      var_name = "@#{$1}s"
      instance_variable_set(var_name, []) if instance_variable_get(var_name).nil?
      instance_variable_get(var_name) << args[0]
    else
      super
    end
  end
end

class AlienSpaceship < Spaceship
  can_have :engines
  can_have :weapons
end

s = AlienSpaceship.make do
  add_engine "Anti-matter NGIN 1"
  add_engine "Anti-matter NGIN 2"
  add_engine "Interdimensional Warp Drive"
  add_weapon "Positron Cannons YKBZ"
end

puts s.engines
puts s.weapons