DCI = Data, communication, Interaction. Lots of this thinking is new to me too
but interesting. I played with BabyIDE a while back when it wasn't very solid.
Time to take another look.
What Jim and Tygrve are talking about largely are object instances playing
roles These have little to do with the objects class. They have everything to
do with the objects behavior and communication in their application. A polygon
could be a background, a connector, or a handle for another object for example.
The PolygonMorph class has little to do with the role the polygon plays or what
messages it needs to receive and send. In squeak 3.9 there was an
implementation of Traits which allowed adding methods that don't belong to a
class. They apparently could be added to objects or classes arbitrarily. In
squeak you can also add an event handler to a object. The event handler allows
the object to behave differently. Handles for polygons are an example. The
event handler gives them a role in relation to the shape of the polygon they
are "handling". It really doesn't matter whether the underlying object is a
polygon or an ellipse the behavior is
determined by the event handler and not the class of the object.
Hth.
Yours in curiosity and service, --Jerome Peace
--- On Sat, 6/25/11, bb <bblo...@arcor.de> wrote:
From: bb <bblo...@arcor.de>
Subject: Re: [Newbies] I don't get it
To: "A friendly place to get answers to even the most basic questions about
Squeak." <beginners@lists.squeakfoundation.org>
Date: Saturday, June 25, 2011, 7:24 AM
Am 21.06.2011 15:46, schrieb Erlis Vidal:
Hi guys,
I was reading recently Jim Coplien ideas about DCI and I was
surprised with the following statement:
"The Smalltalk people, when they put together Smalltalk
originally the computational model was exactly right, in terms
of thinking in terms of objects. And then they screwed it up
with the language. The language is so class focused! Most
languages that we’re saddled with today had made this error."
you can find it here:
http://blog.redtexture.net/2010/06/01/coplien-on-dci-mvc/
Does someone knows what Jim is criticizing? In which sense the
computational model was screwed by the language? I see smalltalk
as a language that express very well the intended computational
model behind.
But that's just me, maybe some of you could help me to understand
Jim's point.
Thanks
Erlis
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As I actually found, there already is an implementation of a
DCI-System in Squeak/Smalltalk. You can find an article, a
documenation and a download on
http://heim.ifi.uio.no/~trygver/themes/babyide/babyide-index.html
Also given is a DCI-Maillist:
object-composition (at) googlegroups.com.
One might be interested in "The Common Sense of Object Oriented
Programming" by Trygve Reenskaug
http://heim.ifi.uio.no/~trygver/2009/commonsense.pdf
Regards
B. Blochl
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