extendable.rb

module Extendable

  def unique_instance_methods
    instance_methods.sort - superclass.instance_methods.sort
  end

  def extend_methods(*methods)
    methods.each do |method_extender|
      method = instance_method(method_extender)

      send(:define_method, method_extender) do
        yield method.bind(self)
      end
    end
  end

  def printable_methods(*methods)                        # ^caller[3]
    extend_methods(*methods) do |method|                 # caller[2]
      method.call.tap do |response|                      # caller[1]
        $stdout.puts "caller: #{caller[3][/`(.+)'/, 1]}" # caller[0]
        $stdout.puts "method: #{method.receiver.class}##{method.name}"
        $stdout.puts "response: #{response.inspect}"
      end
    end
  end

  def rescuable_methods(*methods)
    extend_methods(*methods) do |method|
      begin
        method.call
      rescue Exception => error
        $stderr.puts error.message, *error.backtrace
      end
    end
  end

  def countable_methods(*methods)
    send(:define_method, :method_counter) do
      @method_counter ||= Hash.new(0)
    end

    extend_methods(*methods) do |method|
      method.receiver.method_counter[method.name] += 1
      method.call
    end
  end

  def chainable_methods(*methods)
    extend_methods(*methods) do |method|
      method.call
      method.receiver
    end
  end
end

gistfile1.rb

class Dog

  attr_reader :name, :age

  def alive?
    !!@age
  end

  def born!
    @age = 0
  end

  def advance
    @age += 1
  end

  def initialize(name)
    @name = name
  end

  extend Extendable

  chainable_methods :advance
  countable_methods :alive?
  printable_methods :name, :born!

  extend_methods(:advance) do |method|
    method.receiver.alive? ? method.call : raise("#{name} has not been born yet.")
  end
end

spot = Dog.new('Spot')
spot.name

caller: <main>
method: Dog#name
response: "Spot"
=> "Spot"

spot.name.upcase.to_sym

caller: <main>
method: Dog#name
response: "Spot"
=> :SPOT

spot.advance

RuntimeError: Spot has not been born yet.

spot.born!

caller: <main>
method: Dog#born!
response: 0
=> 0

spot.advance.advance.advance.advance.advance

=> #<Dog:0x007fa6326c8420>

spot.method_counter

=> { :alive? => 6 }