Signal fromm Cpp to QML

Zhitoune

Dear All,

I'm looking to intercept a signal emited from a Cpp object in a QML object, I'm trying to achieve this setting my cpp file as a context Property :

main.cpp

#include "Source.h"

int main(int argc, char *argv[])
{
    QApplication app(argc, argv);
    QQuickView viewer;
    Source source;
    viewer.rootContext()->setContextProperty("source", &source);
    viewer.setSource(QUrl(QStringLiteral("qrc:/main.qml")));
    viewer.show();
    return app.exec();
}

source hinerits from QObject :

source.h

#ifndef SOURCE_H
#define SOURCE_H
#include <QObject>

class Source : public QObject
{
    Q_OBJECT
public:
    explicit Source(QObject *parent = 0);
    signals:
        void dataChanged();
};
#endif // SOURCE_H

Source.cpp :

#include "source.h"

Source::Source(QObject *parent) : QObject(parent), N(256)
{    
    emit dataChanged();    
}

and in my QML file I use Connections :

import QtQuick 2.7

Item {
    id: rootI
    width: 1000
    height: 600
    Connections: {
        target: source
        onDataChanged: {
            console.log("NewData")
        }
    }
}

And on execution I get : "Invalid attached object assignment"

I have looked for the solutions in a lot of document but I still can't find what's wrong with that code....

Fheanor

Hello,

I don't know if this is the best way to do it, but this tutorial works perfectly :
https://andrew-jones.com/blog/qml2-to-c-and-back-again-with-signals-and-slots/

c64zottel

@Zhitoune I assume you are working close to this tutorial:
http://doc.qt.io/qt-5/qtqml-cppintegration-contextproperties.html

But what is the line number where the error occurs?

And what does N(256) do?

Zhitoune

Thanks for our answers,

N(256) is just a remnant of the full code that I cleared for readability.
the error happens at the :

Connections:{

line.

Yes I'm trying to emulate the solution based on the doc.qt without succes so far.

thanks Fheanor, I'll try this solution but I would like to understand why this method is not working.

c64zottel

This post is deleted!

c64zottel

@Zhitoune Try to remove the colon behind Connections. It must be
Connections {

not
Connections: {

Zhitoune

Yup it works fine without the column.
thanks a lot and sorry for this oversight!