Journaling DSL

gistfile1.rb

module Journaling
  def self.included(base)
    base.extend ClassMethods
  end

  module ClassMethods
    def journals
      @journals
    end

    def journal(method_name, block)
      @journals ||= {}
      @journals[method_name] = block

      class_eval do
        alias :"journal_#{method_name}" :"#{method_name}"
      end

      class_eval <<-METHOD
        def #{method_name}(*args)
          value = journal_#{method_name}(*args)
          journal(:#{method_name}, value)
          value
        end
      METHOD
    end
  end

  def journal(method_name, value)
    block = self.class.journals[method_name.to_sym]
    return unless block
    block.call value
  end
end


class JournalTest
  include Journaling

  def meth1
    %w(blank1 blank2 blank3).each do |blank|
    end
  end

  journal :meth1, -> blanks { puts "I ordered #{blanks}" }
end

jt = JournalTest.new
jt.meth1
# => I ordered ["blank1", "blank2", "blank3"]