Hi, I was looking for a way to create object dynamicaly out of a classname. I have the classname which I can convert properly to QMetaType.
If the constructor is Q_INVOKABLE I can use the QMetaObject to create a newInstance() and this work properly into the example. But when this doesn't work, I'm trying to use the QMetaType::create() but totally failed, it does return a pointer, but the memory seem to be bad for this returned pointer. The doc say that QMetaType::create() "If copy is null, creates a default constructed instance". My class does have a default constuctor but just not Q_INVOKABLE, is that the problem? http://doc.qt.io/qt-5/qmetatype.html#create Here's a small sample : QObject *create_child_instance_by_class_name(const char * class_name) { const int type = QMetaType::type(class_name); // MyQObjectDerivatedClass* here and it does return the proper type, check with a instance of the class and this is ok if(type == QMetaType::UnknownType) return nullptr; const auto type_flags = QMetaType::typeFlags(type); if(0 == (type_flags & QMetaType::PointerToQObject)) return nullptr; QObject *instance = nullptr; if(!instance) { // Try default constructor from meta object const QMetaObject* meta_object = QMetaType::metaObjectForType(type); if(meta_object) instance = meta_object->newInstance(); } if(!instance) { // If not working try the meta type create directly void* meta_obj_instance = QMetaType::create(type); // this pointer is bad and uninitialized instance = static_cast<QObject*>(meta_obj_instance); } return instance; } Any idea why??? the create does return a pointer, I follow the code a bit the proper ctor is detected but never seem to be called ?!? and the data are totaly wrong. Note the class is a User type defined by us but does have a default constructor without argument : class MyClass : public QObject { public: MyClass(QObject* parent = nullptr) : QObject(parent) {} ... } QML_DECLARE_TYPE(MyClass); regards, Thanks Jerome
_______________________________________________ Interest mailing list Interest@qt-project.org http://lists.qt-project.org/mailman/listinfo/interest
