ActionScript Developer's Guide to PureMVC

Chapter 7. Applying Business Logic

With the actors of our Model and View tiers now defined, we are ready to stitch them together and get things done. That is certainly the speciality of the Controller tier. But what kind of things do we want to do here?

Two Shades of Logic

Domain Logic

All of that code in ValueObject, AbstractProxy, and their subclasses is Domain Logic. It deals strictly with representing and persisting the data structures of our domain model.

The VOs encapsulate any logic necessary to represent data as typed objects and properties for manipulation by the rest of the program (in this case, marshaling data into and out of an XML structure). Often there is no logic, only properties on the VOs, or XML parsing logic might end up in your Proxys, if it is relatively simple, or in some form of delegate or helper used by the Proxys if there is a lot of it.

The Proxys and VOs take care of persisting and retrieving the data in a reliable way. We do not want to rely on Commands in the application to ensure the integrity of our data or be directly responsible for its persistence.

Business Logic

By contrast, Business Logic has to do with the aims, or business, of the application itself, fulfilling its use cases. For example, opening a Story for editing by taking the StoryVO and making the appropriate calls on the SelectionContext to select the current Draft of the very last Scene in the Story, however its Scenes are grouped. This code works with the domain model data, but for the purpose ...