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copied!<p>In trying to write more testable Java code, I have been using the Model-View-Presenter pattern that Martin Fowler blogged about years ago (<a href="http://martinfowler.com/eaaDev/ModelViewPresenter.html" rel="nofollow noreferrer">http://martinfowler.com/eaaDev/ModelViewPresenter.html</a> -- yeah, I know he deprecated it, but I still like the simplicity).</p> <p>I create a View interface for each JFrame, JDialog, etc. and use a Factory to actually generate them so that I can generate mocks for unit testing.</p> <p>Below is a small set of sample classes and interfaces. Is there a better way in Scala than a straight syntax translation? In other words, how do I use traits, self-type references, etc. to better follow DRY principles and still write type-safe code?</p> <pre><code>import java.awt.Dialog.ModalityType; import java.awt.Window; import java.awt.event.ActionListener; import java.lang.reflect.Constructor; import java.lang.reflect.InvocationTargetException; import javax.swing.JButton; import javax.swing.JDialog; interface View { void okButtonAddActionListener(final ActionListener actionListener); } class Dialog extends JDialog implements View { private final JButton okButton = new JButton("OK"); public Dialog(final Window owner, final ModalityType modalityType) { super(owner, modalityType); } public void okButtonAddActionListener(final ActionListener actionListener) { okButton.addActionListener(actionListener); } } interface ViewFactory<I, C extends I> { I newView(final Window owner, final ModalityType modalityType) throws NoSuchMethodException, InvocationTargetException, InstantiationException, IllegalAccessException; } class AbstractViewFactory<I, C extends I> implements ViewFactory<I, C> { private final Class<C> cls; public AbstractViewFactory(Class<C> cls) { this.cls = cls; } public I newView(final Window owner, final ModalityType modalityType) throws NoSuchMethodException, InvocationTargetException, InstantiationException, IllegalAccessException { final Constructor<C> constructor = cls.getConstructor(Window.class, ModalityType.class); return constructor.newInstance(owner, modalityType); } } class DialogFactory extends AbstractViewFactory<View, Dialog> { private static final class InstanceHolder { public static ViewFactory<View, Dialog> instance = new DialogFactory(); } public DialogFactory() { super(Dialog.class); } public static ViewFactory<View, Dialog> getInstance() { return InstanceHolder.instance; } public static void setInstance(final ViewFactory<View, Dialog> instance) { InstanceHolder.instance = instance; } } // Here is a typical usage in production class DialogFactoryUser { private void userFactory() { final Window window = new Window(null); try { final View view = DialogFactory.getInstance().newView(window, ModalityType.APPLICATION_MODAL); } catch (final Exception ex) { ex.printStackTrace(); } } } // Here is a typical usage in a unit test class Test { public void test() { ... mockView = createMock(View.class); final Window window = new Window(null); mockViewFactory = createMock(ViewFactory.class); expect(mockViewFactory.newView(window, ModalityType.APPLICATION_MODAL)).andReturn(mockView); ... DialogFactory.setInstance(mockViewFactory); } } </code></pre> <p><strong>UPDATE:</strong>: I realized that I asked a <a href="https://stackoverflow.com/questions/2915041/scala-model-view-presenter-traits">similar question</a> last year and got a different "best" answer. Check out the answer by <a href="https://stackoverflow.com/users/4893/sblundy">sblundy</a> -- very nice.</p>

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