How to pass QList from QML to C ++ / Qt?

Question

I am trying to pass a QList integer from QML to C ++ code, but for some reason my approach does not work. When approaching below, the following error appears:

 left of '->setParentItem' must point to class/struct/union/generic type type is 'int *' 

Any input to fix the problem is greatly appreciated.

Below is my code snippet

Header file

 Q_PROPERTY(QDeclarativeListProperty<int> enableKey READ enableKey) QDeclarativeListProperty<int> enableKey(); //function declaration QList<int> m_enableKeys; 

cpp file

 QDeclarativeListProperty<int> KeyboardContainer::enableKey() { return QDeclarativeListProperty<int>(this, 0, &KeyboardContainer::append_list); } void KeyboardContainer::append_list(QDeclarativeListProperty<int> *list, int *key) { int *ptrKey = qobject_cast<int *>(list->object); if (ptrKey) { key->setParentItem(ptrKey); ptrKey->m_enableKeys.append(key); } } 

Answer 1

You CANNOT use QDeclarativeListProperty (or QQmlListProperty in Qt5) with any type other than those obtained from QObject. So int or QString will NEVER work.

If you need to exchange a QStringList or QList or anything that is an array of one of the basic types supported by QML, the easiest way to do this is to use QVariant on the C ++ side, for example:

 #include <QObject> #include <QList> #include <QVariant> class KeyboardContainer : public QObject { Q_OBJECT Q_PROPERTY(QVariant enableKey READ enableKey WRITE setEnableKey NOTIFY enableKeyChanged) public: // Your getter method must match the same return type : QVariant enableKey() const { return QVariant::fromValue(m_enableKey); } public slots: // Your setter must put back the data from the QVariant to the QList<int> void setEnableKey (QVariant arg) { m_enableKey.clear(); foreach (QVariant item, arg.toList()) { bool ok = false; int key = item.toInt(&ok); if (ok) { m_enableKey.append(key); } } emit enableKeyChanged (); } signals: // you must have a signal named <property>Changed void enableKeyChanged(); private: // the private member can be QList<int> for convenience QList<int> m_enableKey; }; 

In the QML side, they simply affect the JS Number array, the QML mechanism automatically converts it to QVariant to make it understandable for Qt:

 KeyboardContainer.enableKeys = [12,48,26,49,10,3]; 

What all!