this context is only usable (set) after this controller has been attached to at least one widget
it always points to the context of the newest widget the controller is used in
if you want to access the context before the controller is attached to a widget, DONT
Discards any resources used by the object. After this is called, the
object is not in a usable state and should be discarded (calls to
addListener will throw after the object is disposed).