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From: Del Archer <darcher@netron.com>
Subject: Re: OO, C++, and something much better!
Date: 1997/01/29
Message-ID: <32EF775C.482D@netron.com>#1/1
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Date: 1997-01-29T00:00:00+00:00
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Robert C. Martin wrote:
> 
> ...
> > In fact it should be an OO sin to ask
> > the type, because, in theory, we don�t want to get intimate with objects
> > we are interacting apart from their interface.
> 
> We typically don't have to ask the type of an object.  In ST, the language
> will do the asking for us at run time.  In C++ the compiler has done it
> at compile time.
> 
> However, there are times both in ST and C++ where we are given an object
> of unknown type and we do not want to send that object a message until
> we *know* it can deal with it.  Thus in ST we use 'respondsTo' and in
> C++ we use 'dynamic_cast'.  Both of these are essentially run time type
> checks that can be applied by the programmer.

I really question the use of 'dynamic_cast'; it makes it difficult to follow the 
open/closed principle.  If a function or method requires a specific type, it 
should only accept objects of that type.


Del.