Should I check QEvent dynamic_cast result if I already checked event->type()?

Question

QEvent has a type() member function which returns the event type as enum value. Should I check dynamic_cast result for QEvent* if I already checked event->type(). E.g.

bool ClassName::eventFilter(QObject* obj, QEvent* event)
{
    if (event->type() == QEvent::KeyPress) 
    {
        auto ke = dynamic_cast<QKeyEvent*>(event);
        if (ke)                                     // <----------- needed?
        {
            // ...
        }
    }
    // ...
}

Is if (ke) condition needed here?

Answer 1

As a commenter suggested, checking out the Qt docs regarding this has the following example:

bool FilterObject::eventFilter(QObject *object, QEvent *event)
{
    if (object == target && event->type() == QEvent::KeyPress) {
        QKeyEvent *keyEvent = static_cast<QKeyEvent *>(event);
        if (keyEvent->key() == Qt::Key_Tab) {
            // Special tab handling
            return true;
        } else
            return false;
    }
    return false;
}

Because specific events will always be guaranteed to return the same type, checking against QEvent::type() is sufficient to allow for a safe static_cast to the target type. This will avoids the RTTI cost that a dynamic_cast would entail.