From: Raul Parolari <raulparolari@...>
Date: 2007-11-18T07:44:04+09:00
Subject: Re: Composition: Build objects from other objects

Pat Maddox wrote:

> 
> I think this is a pretty bad approach.  Consider the following example
> (keep in mind I know nothing about cars):
> 

Pat, 1 hour before your letter, I wrote a clear admission of sin :-)

In particular, there is this sentence in Rick's letter: "a car 'uses' 
the Engine, does not 'behave' as an Engine". That settled the issue.


However, let's remember that there is often another view for modeling 
the world.
I just found in D.Black's book a very pertinent example (p. 172):

module SelfPropelling  # was a Class..
end

class Vehicle
  include SelfPropelling
end

class Truck < Vehicle
end

Of course, I let him elaborate, if he has a chance,

Raul
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