Where is the "Model" In the MVC paradigm of WD4A?

Question

Hi All.
I started WD4A around a month back. I have gone through various tutorials. I have never worked before with an MVC paradigm.
I can now very well visualize a View and a controller - since these are the terms I read and encounter very often in WD4A.
But where does the MODEL fit in?
I asked my friends in WD4J and they say over there they need Model to wrap a BAPI call. In WD4A since there is no need to wrap a BAPI Call, does a model really exist?
Can someone please shed light on this concept? Thanks.

Answer 1

That's right, when working with WDJ, you do need to use a Model to wrap the RFC, BAPI, or web service.  The model in WDA is kind of different.  You know that MVC says that you should have good separation between the UI logic and the business logic, so it is suggest to put all of your business logic in a separate model class.  The term "Model" class is not specific to a certain kind of class, it is simply what the class does, the business logic.  The key thing to remember when creating this class, is that it should inherit from the CL_WD_COMPONENT_ASSISTANCE class.  This allows it to be used as an assistance class in your WDA component.  This gives you direct access to the class via the WD_ASSIST attribute which will be added when defining the assistance class in the WD component overview screen.  Then in your WDA component, you can simply do the business logic by coding....
itab = wd_assist->read_data_from_db.
Of course, you would then have to set the data to the context.
This is basically the Model concept in WDA.
Regards,
RIch Heilman