If I understand you right, you could use Announcements...your "dependent object" registers for Announcements it is interested in, and takes action when something is announced.<br><br>You can see the following for a web type of example, and I could probably get you started with a simple example as well:<br>
<br><a href="http://onsmalltalk.com/programming/smalltalk/maintaining-loose-coupling-in-seaside-components/">http://onsmalltalk.com/programming/smalltalk/maintaining-loose-coupling-in-seaside-components/</a><br><br>Rob<br>
<br><br><div class="gmail_quote">On Fri, May 23, 2008 at 5:44 PM, David Finlayson <<a href="mailto:dfinlayson@usgs.gov">dfinlayson@usgs.gov</a>> wrote:<br><blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">
In the Art and Science of Smalltalk by Simon Lewis, there is a lengthy<br>
discussion of Smalltalk's dependency mechanism (yourObject<br>
addDependent: myObject; myObject changed, etc.) . A few of the<br>
examples of Morphic (Squeak by Example, Squeak: Object Oriented Design<br>
with Multimedia Applications) show examples sending the "changed"<br>
message which I assume triggers a dependency update the same as or<br>
similar to the dependency mechanism described by Lewis. But the<br>
examples are too trivial to see this through completely. Is this still<br>
the way to set up a many-to-one dependency relationship between<br>
objects in Squeak?<br>
<br>
My program is pretty simple: I am creating a navigation display for a<br>
boat. The boat's position and other interesting variables are<br>
transmitted to the program via UDP packets over the network and these<br>
are visualized in the user-interface by a set of widgets (which the<br>
pilot can pick from and move around). I plan on having a master object<br>
that contains the latest information from the various UDP packets and<br>
I want the widgets to depend on the master, so that when (for example)<br>
the position of the boat is updated, the little widget representing<br>
the boat moves appropriately. All of this is obviously do-able (and<br>
not too different than Etoys), but I'm still learning how to set it up<br>
in Squeak.<br>
<br>
Thanks for any advise.<br>
<br>
David<br>
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