[Newbies] I don't get it

Jerome Peace peace_the_dreamer at yahoo.com
Sun Jun 26 05:31:08 UTC 2011

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.


Yours in curiosity and service, --Jerome Peace

--- On Sat, 6/25/11, bb <bblochl at arcor.de> wrote:

From: bb <bblochl at 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 at 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. 




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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



    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





    B. Blochl


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