decorator_magic.rb

module Decorator

  def decorate(decorator_name, &block)
    (class << self; self; end).class_eval do
      define_method(decorator_name) do |method_name_to_decorate|
        with_feature = "#{method_name_to_decorate}_with_#{decorator_name}"
        without_feature = "#{method_name_to_decorate}_without_#{decorator_name}"

        define_method with_feature do
          # call decorator code passing argument of a proc that will call original method
          block.call(proc { send without_feature })
        end

        alias_method without_feature, method_name_to_decorate
        alias_method method_name_to_decorate, with_feature

        method_name_to_decorate
      end
    end

  end
end


class Monkey
  extend Decorator

  decorate :amazing do |orig|
    puts "amazing start"
    orig.call
    puts "amazing end"
  end

  decorate :extra_cool do |orig|
    puts "extra_cool start"
    orig.call
    puts "extra_cool end"
  end

  decorate :super_safe! do |orig|
    begin
      orig.call
    rescue => ex
      puts "Swallowed exception #{ex.message}"
    end
  end

  # super_safe! \
  amazing \
  extra_cool \
  def haha
    puts "HIIII"
#    raise "I am raising!"
  end

end

puts "---------------"

puts Monkey.new.haha