Question

This is our first time using this pattern (we’re not even sure that this pattern is suitable for this project), and me and my mates have a couple of questions.
We’re designing a simple applications for displaying files with regards to permissions.

1. Suppose “Joe” is currently logged in to the system, where would be the correct place to save “Joe” as the active user?

2. What are the roles of the controller in this context? Suppose “Joe” wants to log in to the system. He enters his password and clicks log on, should the view validate the details directly with the Model? or should it ask the controller to do it for him?

3. Suppose that the login is successful, what should happen now? Should the View listen as an Observer to the model and wait for a response that the login is correct and then switch windows? or should the Controller have a method called boolean ValidateLogin() which the view calls and acts accordingly?

As you can see we’re very confused, any help would be appreciated.

Answer 1

1. Session / Database / Configuration File (is this a single or multiple user system?)
2. In some web frameworks*: the view passes the login data to controller, passed to model which would validate, return the result to controller, and give the correct view as response. Surely it’s also fine if the view wants to directly validate the data to the model, but IMO view-model communication should never have any logic involved, only data update notification.
3. I think it’s partially answered in answer 2 above. The controller should be able to destroy/change the login view though (when the login successful, normally the view should change accordingly).

*This is because in web application, usually view cannot directly talk to model, as opposed in desktop application. This is still an MVC, only a variation called MVA.