Role of Model
tmay
via web
I am having some issues in deciding what the roles of my models should be. For example, I am creating an application that has a tool for managing recipes. The data contains categories that have subcategories that have recipes. The tool allows for rearranging and deleting things. The updates will not be committed to the database until the user clicks a save button. I am wondering if I should be updating the model when changes are made, or be updating VOs and not update the model until the data is saved. Right now, the model would not be used outside of this one area and the data is refreshed when this view is loaded to prevent stale data (multiple users can submit recipes); so if the approach to take is not to update the model until a save is done, I am wondering if there is any point to my model. I like the idea of using commands and my model to perform this logic, but am not sure if the model should only represent the saved data. Any advice would be greatly appreciated.
Thanks,
tmay
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Support Staff 2 Posted by Till Schneidereit on 10 Oct, 2011 09:56 PM
If I understand correctly, your model will automatically be reverted
to the old state if you leave the page, making it impossible for
unsaved changes to accidentally escape from it, right? In that case, I
don't see any problems with immediately updating the model instead of
keeping changes somewhere else.
If, on the other hand, you want to be able to do partial roll-backs on
the model's data, I would keep some sort of change list in addition to
the model itself. But either way, I think using a model is the right
thing to do here: It can make sure that your data is always kept in a
valid state and that change events are dispatched and can be managed
by other parts of the app, should the need arise. Imagine, for
example, the later addition of some sort of change view or a view
showing a condensed version of a recipe.
Depending on how exactly you partition your model updating logic, the
line between VOs and models blurs quite easily, anyway: If you keep
all of your updating logic and validation in commands, the model
effectively becomes a big VO. People have very different philosophies
on how that partitioning should look like.
hope that helps,
till
3 Posted by tmay on 11 Oct, 2011 05:38 PM
That sounds like a good solution. Thanks for your help.
Thanks,
tmay
Support Staff 4 Posted by Till Schneidereit on 11 Oct, 2011 06:10 PM
glad i could help