TWISTING THE TRIAD Introduction Widgets

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Tutorial Paper for ESUG 2000. Andy Bower, Blair McGlashan. Object Arts Ltd. Model View Presenter (MVP) is a modern user interface framework for Smalltalk. …

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TWISTING THE TRIAD
The evolution of the Dolphin Smalltalk MVP
application framework.
Tutorial Paper for ESUG 2000
Andy Bower, Blair McGlashan
Object Arts Ltd.
Model View Presenter (MVP) is a modern user interface framework for Smalltalk. Derived from the Taligent
C++ system of the same name. MVP is currently the key UI framework in Dolphin Smalltalk. This paper
discusses the qualities of MVP and why we (the Dolphin design team) chose to adopt it over and above two
previous framework designs (that were tried, and yet rejected) based around “widgets” and Model View Controller
(MVC). We will attempt show how, by rotating (or twisting) the MVC triad, one can produce an “Observer”
based framework that is easy to use and more flexible than those currently available in other Smalltalk
environments.
Introduction
Back in the summer of 1995, we were starting to turn our minds to the creation of a suitable User
Interface model for our new implementation of the Smalltalk language; Dolphin Smalltalk. Our
fledgling VM was working well, the compiler was (for the most part) emitting correctly optimised
bytecodes and most of the Smalltalk-80 base classes had by now…