metaclass / DSL + inheritance

metaclass-black-magic

require 'pp'
module Base

  def metaclass
    class << self 
       self 
    end
  end

  def p_r
    [] # base case
  end
  
  def add(x)
    #p "level => #{self.to_s}"
    metaclass.instance_eval do
      define_method(:p_r) {
          pp caller.first
          puts "#{x} / recurse"
        dat = super()
          puts "#{x} / concat #{dat.inspect}"

        [x].concat dat
      }
    end
  end

end

class Baz
  extend Base

  add :baz

end

class Foo < Baz
  add :foo
end

class Bar < Foo
  add :bar
end

p Foo.p_r
# => [:foo, :baz]

p Bar.p_r
# => [:bar, :foo, :baz]