Unable to access Q_PROPERTY for QML_SINGLETON object.

mossglen90

I have a weird issue where I cannot seem to be able to access any property declared using Q_PROPERTY when using singleton objects.

My code is as follows:
backend.h

#ifndef BACKEND_H
#define BACKEND_H

#include <qqml.h>

#include <QJSEngine>
#include <QObject>

class BackEnd : public QObject {
    Q_OBJECT
    QML_ELEMENT
    QML_SINGLETON

    Q_PROPERTY(QString title READ title WRITE setTitle NOTIFY titleChanged)

   public:
    explicit BackEnd(QObject* = nullptr);
    QString title();
    void setTitle(const QString& title);

   signals:
    void titleChanged();

   private:
    QString m_title;
};

#endif  // BACKEND_H

backend.cpp

#include <backend.h>
#include <iostream>

QString BackEnd::title() {
    std::cout << "Getter";
    return m_title;
}

void BackEnd::setTitle(const QString& title) {
    std::cout << "Setter";
    m_title = title;

    emit titleChanged();
}

BackEnd::BackEnd(QObject*) { m_title = "Initial"; }

main.cpp

#include <QGuiApplication>
#include <QQmlApplicationEngine>

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

    QQmlApplicationEngine engine;
    const QUrl url(QStringLiteral("qrc:/main.qml"));
    QObject::connect(
        &engine, &QQmlApplicationEngine::objectCreated, &app,
        [url](QObject *obj, const QUrl &objUrl) {
            if (!obj && url == objUrl) QCoreApplication::exit(-1);
        },
        Qt::QueuedConnection);
    engine.load(url);

    return app.exec();
}

main.qml

import QtQuick
import QtQuick.Window
import self.backend 1.0 as Backend

Window {
    width: 1600
    height: 800
    visible: true
    title: Backend.title
}

.pro

QT += quick

CONFIG += qmltypes

HEADERS += \
        backend.h

SOURCES += \
        main.cpp \
        backend.cpp

QML_IMPORT_NAME = self.backend
QML_IMPORT_MAJOR_VERSION = 1

resources.files = main.qml 
resources.prefix = /
RESOURCES += resources

When I compile and run the above code, I get the following:

qrc:/main.qml:9:5: Unable to assign [undefined] to QString

If I simply comment out QML_SINGLETON and create a BackEnd { id: backend } in QML, backend.title resolves just fine. But with singleton I am unable to access the property.

Any help would be appreciated.

Thanks

raven-worx

@mossglen90 said in Unable to access Q_PROPERTY for QML_SINGLETON object.:

title: Backend.title

should be

title: Backend.BackEnd.title

and when you dont import it into a separate namespace it would be

title: BackEnd.title

mossglen90

Thank you very much. It works fine now.