When I made my first “Hello World” PlugIn I didn’t care about such things like Data-Workflow or Application Data Tree, I just tried the different features the framework provided. But as the applications became more and more complex and also the amount of different views, perspectives and editors increased I was forced to implement different mechanism to manage all the different data and their presentation. In this article I want to show how to install the Model-View-Controller in your RCP to make a clear software-archictcture and flexible ways for interacting between view and model.

A theoretic discourse

The Model-View-Controller is a paradigma that was developed in the 70s as a result of application-development. In this time the technique was ready for applications with a graphical-user-interface (gui) and a mechanism was needed for handling the new components in a clear way. The Norwegian Trygve Reenskaug developed a schema that is used until in our days and is the most known Design-Pattern. As the name implies the application is divided into three components which have defined communication paths.

The most important things are:

• Views don’t know each other
• The Controller references no views
• The Model references no views
• The View doesn’t manipulate the model
• Only the view knows how to react on which events

Matching the Pattern to RCP Elements

So far so good. But how to match this pattern to your RCP-Application? - Very easy. Just try to find Eclipse-Components that can be used for the special purposes.

• Views are all elements that represents data, e.g. ViewParts, EditorParts, Trees, Tables,…
• Controller can be very easy implemented with JFace Action. Here you have the advantage, that they can be embedded by the framework into views, like Coolbars, Toolbars, ContextMenus,… But they can be also called if a Selection-Event of a SWT-Button is triggered.
• The model is your Business-Model. You just have to add support for PropertyChange-Notfication.

Communication between different Views

An often question is how to communicate different different views? With the MVC no problem: The views are triggering events from the model, therefore its absolutely irrelevant from where the manipulation request came from.

A simple example

I’ve written a small example that should demonstrate in a very simple way the relationships between the different components.

Download

Download the MVC Example as RCP (Source included - 9,3 Mbyte)
CVS-Checkout (more info)