1.4.3 The Controller
The last of the components of MVC, the Controller, has the heavy duty task to make things happen by gathering, validating, and processing User events to modify the state of the application. It operates on the Model in read-write.
Controllers are associated to Views in a strong one-to-one mutual dependency, and can be described as the “business logic” of the View. When the View receives a primary event, it forwards execution to an appropriate Controller method, where the appropriate logic modifies the state of the application held by the Model.
A Controller generally holds a reference to its View and the Models it modifies, and depends strongly on their interfaces and presentation semantics, at least to a degree. It may act on Models that are not the ones observed by the associated View. Like Views, a Controller can be a listener for Model notifications, when the Model state influences how the Controller interprets the User events.
the controller can act on the model, or directly on the view, if it needs to change the visual representation without involving a change in data.
specify that it’s not View == read-only widget vs Controller == read-write widget.