Extending the Presentation Model pattern for a better architecture
27.03.10Filed Under: Flex
When it comes to patterns there is one I always tend to use when writing Flex applications and that is the Presentation Model pattern. Using this pattern I am actually able to unit test most of my UI logic without having to write fragile tests which involve testing the actual UI components.
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However there is one flaw with this pattern when it’s being used on large applications where you might have a scenario where you want to reuse large parts of an application which has one presentation model. When reusing such a component you end up having the same state information as well as the same domain object data. This is obviously not what you want when reusing a UI component and therefor you need to change your presenation model.
Børre Wessel mentions this approach in his Flex in the enterprise talk and his proposed solution of having a separate set of models handling the communication with the server and storing the retrieved data is great. We use this approach on my current project and it has made our architecture better and more robust for changes in the UI. It also makes the Presentation Model classes easier to understand as they end up having just one responsibility: handling the state of UI components.
In my current application the Server Model classes get composed with classes extending Remote Object which makes the class responsible for retrieval and storage of server data. The Server Model classes end up looking a lot like Data Access Objects, in the sense that they have methods for retrieval of data and handle all communication with the data source.
This post is also available as a Adobe Cookbook recipe
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