Attribute Observers

attribute_observers.rb

require "rubygems"
require "bundler/setup"

require "json"

module ProofTest
  class Model
    def self.attr_reader property
      define_method property do
        puts "reading #{attributes[property]} from #{property}"
        attributes[property]
      end
    end

    def self.attr_writer property
      define_method :"#{property}=" do |value|
        attributes[property] = value
        puts "setting #{property} to #{value}"
      end
    end

    def self.attr_accessor property
      attr_reader property
      attr_writer property
    end
    
    def attributes
      class << self
        @attributes ||= Hash.new
      end
    end
  end
end

module ProofTest
  module Person 
    class Model < ProofTest::Model
      attr_accessor :age
      attr_accessor :name
    end
  end
end

david = ProofTest::Person::Model.new

david.name = "David"
david.age = 25

p david

david.attributes.each do |attribute, value|
  puts "Attribute #{attribute} is set to #{value}"
end

puts david.attributes.to_json

Gemfile

source "http://rubygems.org"
gem "json"

Gemfile.lock

GEM
  remote: http://rubygems.org/
  specs:
    json (1.6.6)

PLATFORMS
  ruby

DEPENDENCIES
  json