QThread, QML

? Offline

Hello,
I don't have any problem here, but it is just to have opinions about my method if I am doing it in the correct way.
The idea is to build an application with QML, and use Thread for complex operations.
The main problem is : QML Object can't be in another thread than QMLApplicationEngine.
So, I am using one "WorkerInterface" which own the QThread.
Maybe in this case, it should be better to use QConcurrent ?

It is my code :
"main.qml", simple, just a button

import QtQuick 2.5
import QtQuick.Controls 1.4
import Workers 1.0

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

    SystemPalette {
        id: pal
        colorGroup: SystemPalette.Active
    }

    Worker {
        id: worker;
    }

    Button {
        id: button
        text: qsTr("Process")
        anchors.centerIn: parent

        onClicked: worker.process();
    }

    Text {
        text: worker.data
        anchors.horizontalCenter: parent.horizontalCenter
        anchors.top: button.bottom
        anchors.topMargin: 20
    }
}

Main.cpp

#include <QApplication>
#include <QQmlApplicationEngine>
#include <QQmlContext>
#include <QQmlComponent>
#include "worker.h"

int main(int argc, char *argv[])
{
    QApplication app(argc, argv);
    qmlRegisterType<WorkerInterface>("Workers", 1, 0, "Worker");

    QQmlApplicationEngine engine;

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

    qDebug() << "Main thread : " << QThread::currentThreadId();

    return app.exec();
}

And the worker.h

#ifndef WORKER_H
#define WORKER_H

#include <QObject>
#include <QDebug>
#include <QThread>

class Worker: public QObject {
    Q_OBJECT
public:
    Worker(QString &data) : mData(data) {}

public slots:
    void process() {
        qDebug() << "Process's Thread : " << QThread::currentThreadId();
        mData += "process\n";

        emit processFinished();
    }

signals:
    void processFinished();

private:
    QString &mData;
};

class WorkerInterface : public QObject {
    Q_OBJECT
    Q_PROPERTY(QString data READ getData NOTIFY dataChanged)
public:
    WorkerInterface() : mWorker(mData) {
        mWorker.moveToThread(&mThread);
        connect(this, &WorkerInterface::process, &mWorker, &Worker::process);
        connect(&mWorker, &Worker::processFinished, [this]{
            qDebug() << "ProcessFinished in  : " << QThread::currentThreadId();
            emit dataChanged();
        });

        mThread.start();
    }

    QString getData() const {
        return mData;
    }

    ~WorkerInterface() {
        mThread.exit();
        mThread.wait();
    }

signals:
    void dataChanged();
    void process();

private:
    QThread mThread;
    QString mData;
    Worker mWorker;
};

#endif // WORKER_H

Thanks for your advices :).

benlau

I think QRunnable will be a better choice than QThread.

? Offline

Hello,
I am not very convenient with QRunnable ,so I would rather use QConcurrent than QRunnable ^^.
But this example is just to ask if my way to use thread is the good one, because in my future applications I will have to use a real Object :p.
Thanks for your answer :).