QML/C++ getting info from QML in main.cpp

Question

I'm trying to get info from a new type -Cloud- instantiated in the example.qml from my main.cpp. I have no error of compilation neither of execution. I have only my empty object cloud.

Here my cloud.h

#ifndef CLOUD_H
#define CLOUD_H

#include <QtQuick/QQuickPaintedItem>
#include <QColor>


class Cloud: public QObject
{
    Q_OBJECT
    Q_PROPERTY(QString name READ name WRITE setName)
    Q_PROPERTY(QColor color READ color WRITE setColor)
public:
    Cloud(QObject *parent=0);

    QString name() const;
    void setName(const QString &name);

    QColor color() const;
    void setColor(const QColor &color);


private:
    QString m_name;
    QColor m_color;
};

#endif

Here my cloud.cpp

#include "cloud.h"
#include <QPainter>

Cloud::Cloud(QObject *parent)
    :QObject(parent)
{
}
QString Cloud::name() const{
     return m_name;
}
void Cloud::setName(const QString &name)
{
    m_name = name;
}
QColor Cloud::color() const
{
     return m_color;
}
void Cloud::setColor(const QColor &color)
{
    m_color = color;
}

Here my main.cpp

#include "cloud.h"

#include <QtQuick/QQuickView>
#include <QApplication>
#include <QQmlApplicationEngine>

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

    qmlRegisterType<Cloud>("Sky", 1,0,"Cloud");


    QQmlApplicationEngine engine;
    engine.load(QUrl(QStringLiteral("qrc:/example.qml")));
    QQmlComponent component(&engine,    QUrl((QStringLiteral("qrc:/example.qml"))));
    Cloud *cloud = qobject_cast<Cloud*>(component.create());

    if(cloud){
        qWarning() << "The cloud is "<< cloud->name();
    }else{
        qWarning() << "there is no cloud" <<cloud;
    }

    return app.exec();
}

And finally, here my example.qml

import QtQuick 2.0
import Sky 1.0

Item {
    width: 300
    height: 200
    Item{
        Cloud{
            id:aCloud
            name: "Cumulus"
        }
    }
}

I tried to solve my problem following those tutorials : Defining QML types Extending QML example

Thank you for your help :)

Does it crash on Cloud *cloud = qobject_cast<Cloud*>(component.create()); ? — perencia
– perencia, Commented May 25, 2016 at 8:34

perencia · Accepted Answer · 2016-05-25 12:06:36Z

2

When you do component.create(); you are creating an Item which has Cloud as a child. If you want to get Cloud you should do something like:

QObject* myObject = component.create();
QQuickItem* item = qobject_cast<QQuickItem*>(myObject);
Cloud *cloud = item->findchild<Cloud*>();

EDITED: Updated with coyotte508 remarks.

edited May 25, 2016 at 12:06

answered May 25, 2016 at 9:03

perencia

1,5623 gold badges11 silver badges23 bronze badges

Sign up to request clarification or add additional context in comments.

6 Comments

Cam Over a year ago

That you for your response, but it doesn't work. I have an error "Invalid propery name" on objectname in the example.qml

coyotte508 Over a year ago

@Cam the answer is correct, but forget about the objectName, just do Cloud *cloud = item->findchild<Cloud*>("aCloud"); as aCloud is the id of the Cloud object. Check out this doc. Actually you don't even need to specify the name if there's only one Cloud child, so Cloud *cloud = item->findchild<Cloud*>(); suffices.

Cam Over a year ago

Sorry I made a error on the syntax. Now I have an error "C2783 could not deduce template argument"

Cam Over a year ago

@Coyotte508, I've tried your solution, I don't have any compilation or execution errors, but my object is still empty QObject(0*0)

QObject *myObject = component.create();     QQuickItem *item = qobject_cast<QQuickItem*>(myObject);     Cloud *cloud = item->findChild<Cloud*>("aCloud");

coyotte508 Over a year ago

@Cam, how is your main.qml? Those work for me: pastebin.com/4qQh51z1 <- main.cpp, pastebin.com/zMcKiGFd <- main.qml, and the same example.qml and other files.

|

Cam · Accepted Answer · 2016-05-25 11:42:26Z

0

Thanks to Coyotte508 and perencia I succedded to find what was wrong : in my main.cpp I had a QApplication instead of a QGuiApplication

answered May 25, 2016 at 11:42

Cam

351 silver badge8 bronze badges

Collectives™ on Stack Overflow

QML/C++ getting info from QML in main.cpp

2 Answers 2

6 Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

6 Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related