In a MVC application, should the controller or the model handle data access? [closed]

Question

We are having some philosopical debates in our company about where the calls to the Business Logic should be to perform CRUD operations.

I believe that the Model should consist of your data structure and that the controller should be responsible for populating the data.

My co-worker believes that all population should be done in the model class itself, and simply called by the controller. This keeps the controller neat and clean (but, in my opinion, clutters up the model).

He also believes that any call that returns a Json object should happen in the model, not in the controller. The model would return an array to the controller, which would then return this as a Json object.

What are some different pros/cons to each and is there a right or wrong way to do this?

Answer 1

All business logic should be in the MODEL.

Remember, the responsibilities of each layer are thus:

• Controller - bridge between the model and view. Decides where to go next.
• View - displays the data, gathers user input
• Model - business logic, interface to data store.

One of the biggest gains is in maintenance and (later) expansion. In general:

• If you need to change business logic, you should not need to modify your controller or view.
• If you change your visual display, you should not need to modify your model or controller.
• If you change your workflow, you should not need to modify your view or model.

To do the above, each layer should have no knowledge of the others in order to work properly. For example, the view should receive its data and not need to know anything about where it comes from in order to display it properly. The controller should not need to know anything about the underlying structure of the model in order to interact with it. The model should have no knowledge of how the data is to be displayed (e.g., formatting) or the workflow.

"He also believes that any call that returns a Json object should happen in the model, not in the controller. The model would return an array to the controller, which would then return this as a Json object."

NO. The Model should never format data. It also should not read formatted data. That is polluting the model and moving into the level of hell where business logic = display logic.

JSON (coming in or going out) is just another view. So going out:

Data Store -> Model -> Controller -> View 

Coming in:

View -> Controller -> Model -> Data Store