C ++ Qt基类虚拟析构函数

Question

Do we need a virtual destructor for a classes which are gonna be used in Qt-way: set QObject -parent which will call in QObject's destructor deleteLater() or something like that for any object for which it was set as parent?

For example:

class MyWidget : public QWidget {
public:
    MyWidget() {
        w = new QWidget(this);
        // "w" will be deleted automatically by parent MyWidget::QWidget::QObject's destructor afaik
    }
private:
    QWidget *w;
}

Do we need a virtual destructor for MyWidget class if it is gonna be inherited? I see no reason for this because it does not delete anything and each property of the class which is derived from QObject will be deleted from MyWidget::QWidget::QObject 's destructor.

Answer 1

如果您添加或不添加它并不重要，因为QWidget继承的QObject具有虚拟析构函数，并且它在整个层次结构中传播。

Answer 2

You don't need to explicitly write an (empty) virtual destructor because QWidget already marks its distructor as virtual , so automatically all destructors of the class hierarchy are virtual .

But in general, if you write a class that is going to be inherited (and doesn't already have a base class with a virtual destructor), always specify a virtual destructor, otherwise things will blow up badly if anyone tries to destroy an object of your class hierarchy through a pointer of the base class type.