thoughtbot

public interface Collection {

    Collection <<(Object anObject);

}

thoughtbot

public class Array implements Collection {

    public Collection << (Object object) {
        // add object to me
    }

}

public class String implements Collection {

thoughtbot

class Address < ActiveRecord::Base
end

class Person < Address
end

class Company < Address
end

thoughtbot

class Addressable < ActiveRecord::Base
end

class Person < Addressable
end

class Company < Addressable
end

thoughtbot

class Addressable < ActiveRecord::Base

  has_one :address

end

thoughtbot

addressables (id)

people (id, name, age, height, weight, addressable_id)

companies (id, size, established_date, addressable_id)

addresses (id, street, city, state, addressable_id)

thoughtbot

module Addressable
end

module Taggable
end

class Person < ActiveRecord::Base
  
  include Addressable

thoughtbot

module Addressable

  has_one :address

end

thoughtbot

module Addressable

  def self.included(klazz)  # klazz is that class object that @include@d this module
    klazz.class_eval do
      has_one :address
    end
  end

end

thoughtbot

addresses (id, street, city, state, person_id, company_id)