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POApproaches to creating the View for "Humble Dialogs"
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copied!<p>I have a bunch of questions to post regarding the issue of separating the view from logic when creating a GUI.<br> The following is a minimal example of what I would do for a simple dialog that has a label and a button using the "Humble Dialog" approach. Pressing the button should show some text on the label. I have used C++ an Qt that I am comfortable with but I guess it is readable by all other audiences.<br> In any case I am interested in possible side effects because of the choice of language (I am using C++ in the project I am interested in introducing this).</p> <pre><code>class IView { public: IView(){} virtual ~IView(){} virtual void showResult(const QString &text)=0; }; class Presenter { public: Presenter(IView *view){ m_View = view; } ~Presenter(){} void buttonPressed(){ QString text; // Evaluate text m_View->showResult(text); } private: IView *m_View; } // Multiple inheritance. Is this OK? class MyView : public QDialog, public IView { public: MyView(){ m_Presenter = new Presenter(this); m_Button = new QPushbutton(this); m_Label = new QLabel(this); // Ui event handled inside view but then directly // propagated to the Presenter connect(m_Button,SIGNAL(clicked()),this,SLOT(buttonPressed())); } ~MyView(){ delete m_Presenter; // Qt will automatically delete m_Button and m_Label; } void showResult(const QString &text){ m_Label->setText(text); } protected slots: void buttonPressed(){ m_Presenter->buttonPressed(); } private: Presenter *m_Presenter; QPushbutton *m_Button; QLabel *m_Label; } class TestView : public IView { public: TestView(){} ~TestView(){} void showResult(const QString &text){ m_LabelText = text; } QString getResult(){ return m_LabelText; } private: QString m_LabelText; } // Test code TestView view; Presenter presenter(&view); presenter.buttonPressed(); EXPECT_EQ(view.getResult(),"Expected Result"); // Procuction code MyView view; view.show(); </code></pre> <p>Now this is what I got by following the <a href="http://www.objectmentor.com/resources/articles/TheHumbleDialogBox.pdf" rel="nofollow noreferrer">initial work on the Humble dialog by Feathers</a>. The approach that I would get from <a href="http://codebetter.com/blogs/jeremy.miller/pages/129546.aspx" rel="nofollow noreferrer">Fowler's implentation</a> would be to avoid creating the instance of the Presenter class in the constructor of MyView but pass it as a parameter instead so the production code would look like the test code. I personally like the approach I present here.</p> <p>So,</p> <ul> <li>Is it meant to be used with multiple inheritance (see my comment in MyView class)?</li> <li>Should the events be propagated directly to the Presenter or should they be handled in the view that will call the respective presenter action (as I have done here to avoid having to make the Presenter a QObject so it can handle UI events)?</li> <li>Are there any other remarks?</li> </ul>

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