The program has components that are responsible for a certain functionality. The component is implemented using MVC, (Model, Controller, View classes). There is a main window class MainWindow. Each Controller class connects to it. It is necessary that each Controller has access to another, even to the model.
The solution may be to create an Application class in which all Controller classes and MainWindow are connected. Make a namespace in which to make a function that will return a pointer to an Application object. Through specify access to the Controller is obtained.
In Controller, make a public model () method that returns the model.