3.2 Hierarchic Model View Controller (HMVC, Recursive MVC)
Hierarchic MVC is a strategy to apply MVC in large applications while keeping control of the granularity of data and communication. HMVC deploys a hierarchy of triads by connecting controllers. The triads work together by handling events they can handle, and forwarding them up in the hierarchy when they don’t know how to handle
There are relevant differences when compared with traditional MVC: the view is responsible for handling user input events. These events are forwarded to the controller. The controller as usual performs modification on the model through direct method call on model objects To refresh the view state, the controller notifies the view that it needs refresh. The view then communicates directly with the model, pulling the data from it without involving the controller further.  Alternatively, the model notifies the view by providing its own state  The controller also acts as a hub in the controller hierarchy. If a controller receives an event from its associated view that cannot be handled, it is bubbled to the parent, which in turn can choose to handle it or delegate it further up or down in the tree. Any model at any level in the hierarchy can access data at any scope, and models can also talk to each other. Controllers at any level in the hierarchy can share these models.
controller has another controller as view controller handle multiple views or multiple sub controllers
View-model in a observer pattern