From: Ned Konz <ned@...>
Date: 2001-11-17T02:50:26+09:00
Subject: [ruby-talk:25549] Re: Something strange with Ruby's inheritance mechanism

On Friday 16 November 2001 08:11 am, Eric Jacoboni wrote:

> That's exactly my problem : A is a subset of B. A subset of objects: a
> A object is always a B object, the opposite is not necessary true. My
> first post was about the lack of this concept in Ruby: dynamic typing
> prevents it as an A object may become, say, an Integer. 

No. An A object is going to remain an instance of A (or very closely related 
class if you add methods directly to the instance). Now a variable (i.e. 
name) that once was bound to an A object may later refer to an integer; there 
is nothing that requires variables to point to a particular kind of object. 
However, objects and variables are two very different things.
 
> As beginner in
> Ruby, the surprise comes from the fact that the OOP is ok as long as
> we stay at the class level but disappears when we come to instances
> (object) because of dynamic typing. This trouble comes from my
> experience with strong typing languages.

Ruby (like Smalltalk) has strong typing, stronger than (say) C++. In Ruby, 
everything, even numbers, know what type they are.

However, variables can refer to objects of any type.

-- 
Ned Konz
currently: Stanwood, WA
email:     ned@bike-nomad.com
homepage:  http://bike-nomad.com