How to get access to QList<QPair<int, double>> in QML

Praveen.Illa

Hi Team,

I am newbie to the Qt world and trying to learn Qt by doing small sample programs.
How can I access QList of C++ elements in QML. Please find sample program

sample.h
class Sample : public QObject
{
Q_OBJECT
Q_PROPERTY(QList<QPair<int, double>> sendList READ sendList)
public:
explicit Sample(QObject *parent = nullptr);
void prepareList();
QList<QPair<int, double>> sendList();

private:
QList<QPair<int, double> > m_list;
};

sample.cpp

float g_f[5] = {1.5,2.5,3.5,4.5,5.5};
int g_i[5] = {1,2,3,4,5};

Sample::Sample(QObject *parent) : QObject(parent)
{
}

void Sample::prepareList()
{
for(int iLoop = 0; iLoop < 5; iLoop++)
{
m_list.append(qMakePair(g_i[iLoop], g_f[iLoop]));
}
}

QList<QPair<int, double> > Sample::sendList()
{
return m_list;
}

main.cpp
int main(int argc, char *argv[])
{
QCoreApplication::setAttribute(Qt::AA_EnableHighDpiScaling);
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);
*/
Sample obj;
obj.prepareList();

qmlRegisterType<Sample>("Sample", 1, 0,"Sample");
engine.rootContext()->setContextProperty("obj", QVariant::fromValue(&obj));

engine.load(url);
return app.exec();

}

main.qml
Window {
width: 640
height: 480
visible: true
title: qsTr("Hello World")

Component.onCompleted: {
    console.log("Component Oncompleted")
    for(var i = 0; i < 5; i++)
        console.log("i = " + i + " Val = " + obj.sendList[i])
}

}

sierdzio

Please wrap your code in code tags:

```
someCode();
```

QML engine does not understand QPair, you need to use something else, like a QVariantMap or custom subclass of QAbstractItemModel.

Praveen.Illa

@sierdzio
Thanks for your quick response
Can you please provide some pseudo code how to implement and expose QVariantMap to QML.
Any references is appreciated

sierdzio

I think this article in the documentation should help: https://doc.qt.io/qt-5/qtquick-modelviewsdata-cppmodels.html

Praveen.Illa

@sierdzio
I think the url you provided is using a model.
Is it possible to expose the QVariantList in the form of ( QList<QPair<int, double>>) to QML without using models.
Can someone please provide a sample examples