From: Piotr Szotkowski <chastell@...>
Date: 2011-01-05T14:07:50+09:00
Subject: replacing inheritance with module inclusion, oh my

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The problem: a Person should be an OpenStruct-like Entity, with the
Entity being taking care of the Person=E2=80=99s OpenStruct-ness and persis=
tence
(say, for starters, the Person being added to a pool of Entities).

Tentative approach with inheritance:



require 'ostruct'

class Entity < OpenStruct
  def initialize *args
    puts 'Entity#initialize'
    super
    puts "adding #{self} to pool"
  end
end

class Person < Entity
  def initialize *args
    puts 'Person#initialize'
    super
  end
end

Person.new name_prefix: 'Dr', given_names: ['Horace'], surname: 'Worblehat'



Result:

Person#initialize
Entity#initialize
adding #<Person name_prefix=3D"Dr", given_names=3D["Horace"], surname=3D"Wo=
rblehat"> to pool



The problem: how about making Entity a module so not to
require Person to inherit from it. Something like the below:



require 'ostruct'

module Entity
  def initialize *args
    puts 'Entity#initialize'
    super
    puts "adding #{self} to pool"
  end
end

class Person < OpenStruct
  include Entity
  def initialize *args
    puts 'Person#initialize'
    super
  end
end

Person.new name_prefix: 'Dr', given_names: ['Horace'], surname: 'Worblehat'



Result:

Person#initialize
Entity#initialize
adding #<Person name_prefix=3D"Dr", given_names=3D["Horace"], surname=3D"Wo=
rblehat"> to pool



The real problem: how to move the OpenStruct-ness of Entities away from
Person and into the Entity? You can=E2=80=99t include/extend Entity into/wi=
th
OpenStruct (because OpenStruct is not a module) and you can=E2=80=99t make
Entity inherit from OpenStruct (because Entity is a module).

I=E2=80=99m fine with, say, any Entity.new + Entity.included
(not-really-)magic required or some such, I just can=E2=80=99t
seem to be able to put my finger on the needed wiring=E2=80=A6 :)

(A cherry on the top would be if Person#initialize did not
have to remember to call super; I want Person to be as simple
as possible and offload as much as possible to Entity.)

=E2=80=94 Piotr Szotkowski
--=20
=E2=80=98The Ruby community should proceed with all deliberate
speed towards ISO standardization of the language.=E2=80=99
=E2=80=98Yeah, look what it did to Forth.=E2=80=99
=E2=80=98Don=E2=80=99t just say it, show it: <http://vividpicture.com/aleks=
/atari/forth.jpg>=E2=80=99
            [M. Edward (Ed) Borasky, Matt Lawrence, Gregory Brown, ruby-tal=
k]




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