What is the right MVC diagram for a web application?

Question

Which MVC diagram is correct? Each have different arrows...

Diagram 1

Answer 1

None of them is actually wrong, but there is a different approach for Web (request/response) based MVC and client side MVC.

In a web environment a controller is responsible for dealing with a users request, modifying the model (if applicable), finding the right view, assigning that model information to the view and returning it to the user.

In the more direct interpretation of the original MVC pattern (speak desktop applications) the model updates the view directly, whenever it changes, and the controller deals with user input and application logic updating the model accordingly. This doesn't work for normal web applications though, since HTTP is stateless and without using any other more recent technology (like long polling Ajax or websockets as mentioned in the comment) the server can't really notify the client about changes in the model.