From: Konrad Meyer <konrad@...>
Date: 2007-11-17T14:06:04+09:00
Subject: Re: Composition: Build objects from other objects

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Quoth Thufir:
> <http://www.javaworld.com/javaworld/jw-06-2001/jw-0608-java101.html> has=
=20
> a discussion of composition versus inheritance which I'm trying to apply=
=20
> to ruby.  For discussions sake, I'll use the classes discussed in the=20
> above linke:  Car, Vehicle and Engine.  Car inherits from Vehicle, of=20
> course.
>=20
> Let's say that Engine is something like:
>=20
> class Engine
> 	attr_accessor :type
>=20
>=20
> 	def initialize ()
> 		@type =3D "generic engine"
> 	end
>=20
> 	def vroom ()
> 		puts "vroooooom"
> 	end
> end
>=20
> Vehicle would be something like:
>=20
> class Vehicle
>=20
> 	attr_accessor :engine
>=20
> 	def initialize ()
> 		@engine =3D Engine.new
> 	end
> end
>=20
>=20
> class Car < Vehicle
>=20
> 	def initialize ()
> 		super()
> 	end
> end
>=20
> then from IRB for instance:
>=20
> vw_bug =3D Car.new
>=20
> then can you make the vw_bug go "vroooooom" and so forth?  What would be=
=20
> the usual way to do this in ruby?  When a car is instantiated, should an=
=20
> engine object get passed to the initializer method?
>=20
> thanks,
>=20
> Thufir

vw_bug.engine.vroom() should return "vroooooom" if that's what you mean.

Sorry, I'm having trouble understanding the question.

Regards,
=2D-=20
Konrad Meyer <konrad@tylerc.org> http://konrad.sobertillnoon.com/

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