Newsgroups: comp.lang.smalltalk
Path: cantaloupe.srv.cs.cmu.edu!rochester!cornell!travelers.mail.cornell.edu!news.kei.com!news.mathworks.com!uunet!in1.uu.net!boole!uri
From: uri@boole.com (Uri Eshkar)
Subject: Re: VW2.0 expressInterestIn: for:endBack:
Message-ID: <1995Feb15.192819.18516@boole.com>
Organization: Boole & Babbage, Inc.
References: <3hqsc9$ncl@ubszh.fh.zh.ubs.com>
Date: Wed, 15 Feb 1995 19:28:19 GMT
Lines: 22

In <3hqsc9$ncl@ubszh.fh.zh.ubs.com> dmp@ubszh.net.ch (G.Dempsey (by ubsswop)) writes:


>I am new to VisualWorks Smalltalk and have a question about DependencyTransformers and the expressInterestIn:for:sendBack method.  They seem to be quite useful, but are not used in the ParcPlace code.  Is there are reason for this?  When should/n't they be used?  Perhaps some could post an explanation of what they are for because the documentation seems to be pretty thin.

>Thanks.
>Greg
DependencyTransformers were introduced to get better control on dependencies,
that were heavily used in MVC.
I believe they are not used, because they have been replaced by even more
advances constructs. a ValueModel allows an object to express an individual
interest in a specific aspect encapsulated by the value model (the method
onChangeSend:to: ). 
There was an excellent article on these things in one of the latest issues of
the Smalltalk Report. 

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  Uri Eshkar	Boole & Babbage
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  Email:	uri@boole.com

