thoughtbot

class Address < ActiveRecord::Base

   # here's where we'll use Addressable
   belongs_to :addressable, :polymorphic => true    

end

class Tagging < ActiveRecord::Base

thoughtbot

public interface Addressable {

    Address getAddress ();

    void setAddress (Address address);

}

public class Address {

thoughtbot

public interface Taggable {

    Collection getTaggings ();

}

public class Tagging {

    private Taggable taggable;    // anyone who implements Taggable

thoughtbot

class Person < ActiveRecord::Base

  has_one :address, :as => :addressable

end

class Company < ActiveRecord::Base

  has_one :address, :as => :addressable

thoughtbot

class  Address < ActiveRecord::Base

  belongs_to :person
  belongs_to :company

end

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