Initialize uncopyable third-party base class, with pointer to object

Question

I'm fighting with Qt. Cannot find out reliable solution for my specific problem.

We have custom class MyWidget that must:

• be derived from QWidget to override closeEvent method
• have fields that must be initialzed in constructor

Problems:

• QWidget's guts initialized with QUiLoader from .ui file. So I have only QWidget* pointer
• QWidget is non-copyable.
• QWidget has no move constructor

The code (error checking and memory management are omitted for simplicity):

class MyWidget : public QWidget
{
    bool m_Closed;
public:
    MyWidget(QWidget* qw) : 
        QWidget(*qw), // error: copy constructor is private
        m_Closed(false)
    {}

    bool IsClosed() const { return m_Closed; }

    virtual void closeEvent(QCloseEvent *) override { m_Closed = true; }
};

QFile file("main.ui");
QUiLoader uiLoader;
MyWidget* uiMain = new MyWidget(uiLoader.load(&file));
uiMain->show();

Questions:

• How can I workaround this? I feel that solution is very simple.
• Can I use move semantics here somehow?

Note that:

• I cannot make QWidget member, as I need to override its method.
• Probably, I can make some MyWidget::Init() method, to init those bool flag, which must be called after each instantiation. But I find this solution unreliable.
• In the end, I must just have QWidget, that I can check if it was closed or not (maybe you know another, simple way)
• I use MSVC 2013 RC and GCC 4.8.1, so C++11 solution would be great

Do not hesitate, I appreciate any suggestions and criticism.

Answer 1

.ui files can use custom classes that derive from QWidget, so you can use your class in the Designer - even without writing any Designer plugins (it won't be shown). Right-click on a widget and select "Promote".

You need to create your own derived version of QUiLoader, and provide an implementation of the factory method QUiLoader::createWidget that can create your widgets. See this answer for a complete example.

Then you put your initialization code in the derived widget.