c++ and qml .. modifying properties need help

[antemort]

Hi need help to solve my problem. I have established a qml and cpp project - qt quick application, and want to use something like http://doc.qt.io/qt-4.8/qtbinding.html#receiving-signals under modifying properties.

I want to change value of a property:

property int angle1:

in my .qml- file

from a cpp file that receive emitted data via TCPserver. The data recieved shall be the value of the property in .qml.

hope i explained it right.

my code looks like:

main.qml in qrc:

property int angle1:

myserver.cpp

#include "myserver.h"

#include <QSignalMapper>
#include <QTcpServer>
#include <QTcpSocket>
#include <QQmlApplicationEngine>
#include <QQmlComponent>


MyServer::MyServer(QObject *parent) : QObject(parent)
{
    QQmlApplicationEngine engine;
    engine.load(QUrl(QStringLiteral("qrc:/main.qml")));
    QObject *rootObject = engine.rootObjects().first();
    GUI = rootObject->findChild<QObject*>("GUI");

    server = new QTcpServer(this);
    connect(server, SIGNAL(newConnection()), this, SLOT(newConnection()));
    if(!server->listen(QHostAddress::LocalHost, 8001)) {
        qDebug() << "Server could not start.";
    } else {
        qDebug() << "Server started.";
    }
}

void MyServer::newConnection() {
    qDebug() << "Client connected";
    QTcpSocket *socket = server->nextPendingConnection();

    // Ugly hack!
    this->socket = socket;
    connect(socket, SIGNAL(readyRead()),this, SLOT(readyRead()));
    sendData("Welcome client!\r\n");
}

void MyServer::sendData(std::string data) {
    const char * rawData = data.c_str();
    socket->write(rawData);
    socket->flush();
    socket->waitForBytesWritten(3000);
}

void MyServer::readyRead()
{
        qDebug() << "Reading data...";
        QByteArray data = socket->readAll();
        qDebug() << data;
        emit dataRecievedFromServerApp(data);
        //QObject *object = view.rootObject();
        //QObject *angle1 = GUI->findChild<QObject*>("angle1");
        //angle1->setProperty("angle1", 160);
        qDebug() << "Done reading data.";
        sendData("Server received data, thank you!\r\n");
}

void MyServer::onDisconnected()
{
    socket->close();
}

main.cpp

#include <QApplication>
#include <QQmlApplicationEngine>
#include <myserver.h>

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

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

    return app.exec();
}

myserver.h

#ifndef MYSERVER_H
#define MYSERVER_H

#include <QObject>
#include <QDebug>
#include <QTcpServer>
#include <QTcpSocket>

#include <QHostAddress>
#include <QObject>
#include <QSignalMapper>

class MyServer : public QObject
{
    Q_OBJECT
public:
    explicit MyServer(QObject *parent = 0);
    void sendData(std::string data);

signals:
    void dataRecievedFromServerApp(QByteArray data);

public slots:
    void newConnection();
    void readyRead();
    void onDisconnected();

private:
    QTcpServer *server;
    QTcpSocket *socket;
    QObject *GUI;
    QSignalMapper *m_readyReadSignalMapper;
    QSignalMapper *m_disconnectedSignalMapper;
};

#endif // MYSERVER_H

[p3c0]

@antemort So what is the error ? Are you able to find that property ?

[antemort]

@p3c0 the error is Component is not ready and when I try to change it crashes :(

[p3c0]

@antemort That means there is some error in the QML due to which the engine is not able to load it.

[antemort]

when i run the application like above it comes no errors and it run the program but I have not solve the problem to get the property in qml to be the value of "data" in

emit dataRecievedFromServerApp(data)

in myserver.cpp

but when I try with

       QObject *object = view.rootObject();
      QObject *angle1 = GUI->findChild<QObject*>("angle1");
      angle1->setProperty("angle1", 160);

it stops work

[p3c0]

@antemort First check if that QML contains no error. Secondly you need to findChild in the rootObject

QQuickItem *rootItem = view.rootObject(); //root item in QML
QQuickItem *child = parent->findChild<QQuickItem*>("childobjectname"); //find child of that root object using its objectName
child->setProperty("angle1", 160); //set property angle1 to 160