Question

I have two UI components as follows:

class UIPanel extends JPanel{ ... }

class MainPanel { Model m;
    //instantiates UIPanel }

Issue here is that in UIPanel class I would like to add an ActionListener that would use Model to make decisions on how to process user action. Unfortunately I decided to split the two classes and I do not have access to Model directly. An obvious solution is to simply stick the UIPanel class inside the MainPanel, but I was thinking whether there was a way to keep the split.

Answer 1

You could simply give UIPanel a reference to the Model:

class UIPanel {
    UIPanel(Model m) {
         m.addActionListener(listener);
    }
}

class MainPanel {
    ...
    MainPanel() {
        ...
        UIPanel uiPanel = new UIPanel(m); // Constructor, a separate setter would be possible also
        ...
     }
}

This obviously is a quite tight coupling. Maybe MainPanel does not need the reference to the Model at all?