'QQmlListProperty<int>' is not registered?

cesupa

I want to use QQmlListProperty to access list-values in QML. The class where I register the list with

@ Q_PROPERTY(QQmlListProperty<int> items READ items)
@

is a singleton class. I register it with

@ qmlRegisterSingletonTypeAppointment::MVC::ApModel("appointment.model.apmodel",1,0,"ApModel",Appointment::MVC::apModelSingletonTypeProvider);
@

in my main.cpp. The usage of other properties works fine, but when I want to access the list, QML prints out the following error:

QMetaProperty::read: Unable to handle unregistered datatype 'QQmlListProperty<int>' for property 'Appointment::MVC::ApModel::items'

Did I forget something?

cesupa

I have done some tests with a little example class:

@#include <QObject>
#include <QQmlListProperty>

class ListItem : public QObject
{
Q_OBJECT
Q_PROPERTY(QString name READ name WRITE setName NOTIFY nameChanged)
public:
ListItem();

QString name() const;
void setName(const QString &name);

signals:
void nameChanged();

private:
QString _name;
};

class QmlListTest : public QObject
{
Q_OBJECT
Q_PROPERTY(QQmlListProperty<ListItem> items READ items)

public:
explicit QmlListTest(QObject *parent = 0);

QQmlListProperty<ListItem> items()
{
    return QQmlListProperty<ListItem>(this,_items);
}

signals:

public slots:

private:
QList<ListItem*> _items;

};@

@#include <QApplication>
#include <QQmlApplicationEngine>
#include <QtQml>
#include "qmllisttest.h"

int main(int argc, char *argv[])
{
QApplication app(argc, argv);

QQmlApplicationEngine engine;

qmlRegisterType<QmlListTest>("qmllisttest",1,0,"List");
qmlRegisterType<ListItem>("qmllisttest",1,0,"ListItem");

engine.load(QUrl(QStringLiteral("qrc:///main.qml")));

return app.exec();

}@

@import QtQuick 2.2
import QtQuick.Controls 1.1
import qmllisttest 1.0

ApplicationWindow {
visible: true
width: 640
height: 480
title: qsTr("Hello World")

property ListItem item: List.items[0]

Text {
    text: qsTr(item.name)
    anchors.centerIn: parent
}

}@

That's the way how I want to access the list in QML. But somehow the List.items property is undefined in QML:

@
qrc:///main.qml:12: TypeError: Cannot read property '0' of undefined
qrc:///main.qml:15: TypeError: Cannot read property 'name' of null
@

Is there another way to access a list generated in C++ in QML like above?

cesupa

Okay, I have found the solution:

In my example class I had to set an instance of the class in the root context as property of course.

In my singleton class I just had to add the namespaces in the Q_PROPERTY declaration.

lunamystry

Hi, I have the same error and I don't understand what the quoted text means. I would like the lifetime of my Object to be controlled by qml and it is not a singleton.

[quote author="cesupa" date="1402306240"]Okay, I have found the solution:

In my example class I had to set an instance of the class in the root context as property of course.

In my singleton class I just had to add the namespaces in the Q_PROPERTY declaration. [/quote]

chrisadams

Hi,

Instead of using QQmlListProperty, can you simply define a Q_PROPERTY of the QList<int> type? You should still be able to access elements of the sequence via subscript operator / index, and the metatypes should definitely be registered by the engine.

Thanks,
Chris.

http://www.qinetic.com.au/ - The Qt And QML User Experience Specialists

lunamystry

@chrisadams that works thank you. After reading your post, I realise that it is actually mentioned in the docs: http://qt-project.org/doc/qt-5/qtqml-cppintegration-exposecppattributes.html

[quote]
Properties containing lists of QObject-derived types can also be exposed to QML. For this purpose, however, one should use QQmlListProperty rather than QList<T> as the property type.
[/quote]
I was not reading the docs in enough detail to see on my first 5 readings :-}

[quote author="chrisadams" date="1411524542"]Hi,

Instead of using QQmlListProperty, can you simply define a Q_PROPERTY of the QList<int> type? You should still be able to access elements of the sequence via subscript operator / index, and the metatypes should definitely be registered by the engine.

Thanks,
Chris.

http://www.qinetic.com.au/ - The Qt And QML User Experience Specialists[/quote]