How to send Qt signals with non basic types to a QML script

Tom C

Hello !!

I have two classes, Map and Position, both are derivate from QObject.
I have a QML script which display a Position object.

I'm trying to send a signal (from a Map object) holding a Position object to update my QML srcipt. But i got the following message when the signal occurs:

bq. QMetaProperty::read: Unable to handle unregistered datatype 'Position' for property 'QDeclarativeBoundSignalParameters::newPosition'

bq. app.qml:10: TypeError: Result of expression 'newPosition' [undefined] is not an object.

Here my code:

@
#ifndef POSITION_H
#define POSITION_H

#include <QObject>

class Position : public QObject
{
Q_OBJECT
Q_PROPERTY(double latitude READ latitude WRITE setLatitude)
Q_PROPERTY(double longitude READ longitude WRITE setLongitude)

public:
Position(double latitude = 0, double longitude = 0,QObject *parent = 0);
Position(const Position & other);
Position & operator =( const Position & other);
bool operator !=(const Position &);

double latitude();
void setLatitude(double);

double longitude();
void setLongitude(double);

private:
double m_lat;
double m_lon;
};

#endif // POSITION_H
@

@
#ifndef MAP_H
#define MAP_H

#include <QObject>

#include "position.h"

class Map : public QObject
{
Q_OBJECT

Q_PROPERTY(Position center READ center WRITE setCenter NOTIFY centerChanged)

public:
explicit Map(QObject *parent = 0) :
QObject(parent)
{}

Position center() const{
    return m_center;
}
void setCenter(const Position & other){
    if( m_center != other ){
        m_center = other;
        emit centerChanged(m_center);
    }
}

signals:
void centerChanged(Position newPosition);

private:
Position m_center;
};

#endif // MAP_H
@

@
import QtQuick 1.0
import Localisation 1.0

Item {
width: 300; height: 200

Connections{
    target: myMap
    onCenterChanged: {
        //perform action with newPosition, e.g :
        text.text = newPosition.latitude + ", " + newPosition.longitude
    }
}

Text{
    id: text
    anchors.centerIn: parent
    text: "Wait an update"
}

}
@

@
#include <QApplication>
#include <QtDeclarative>
#include <QDeclarativeView>

#include "map.h"
#include "position.h"

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

qmlRegisterType<Position>("Localisation",1,0,"Position");

Map myMap;
QDeclarativeView view;
view.rootContext()->setContextProperty("myMap",&myMap);
view.setSource(QUrl::fromLocalFile&#40;"app.qml"&#41;);
view.show();

return a.exec&#40;&#41;;

}
@

dmcr

Hello,

first of all, i would use QDeclarativeItem instead of QObject for using an object in QML.

Then i may use the object connections, but the target had to be an QML item, which is not exactly in your code (it is more a "binding" done with setContextProperty)

tolszak

Try with:

@
qmlRegisterType<Position>();
@

and if it doesn't work maybe additionally with:

@
qmlRegisterType<Map> ();
@

MichK

You know that instead of adding new clas you could use QPointF:
@
//.h file
class Map : public QObject
{
Q_OBJECT
Q_PROPERTY(QPointF center READ getCenter NOTIFY centerChanged)

public:
explicit Map(QObject *parent = 0);

inline QPointF getCenter() const;
void setCenter(const QPointF& aCenter);

signals:
void centerChanged();
public slots:
void blabla();

private:
QPointF m_center;
};

QPointF Map::getCenter() const
{
return m_center;
}

//.cpp file
void Map::setCenter(const QPointF &aCenter)
{
if (aCenter == m_center)
return;

m_center = aCenter;
emit centerChanged();

}

//Part of qml file
Connections {
target: myMap
onCenterChanged: {
myTxt.text = "x " + myMap.center.x + " y " + myMap.center.y
}
}
@

If you want to use longitude and latitude keywords you can do:
@
//.h file
Q_PROPERTY(QVariant center READ getCenter NOTIFY centerChanged)
//...
QVariant getCenter() const;

//.cpp file
QVariant Map::getCenter() const
{
QMap<QString, QVariant> centerMap;
centerMap.insert("longitude",m_center.x());
centerMap.insert("latitude",m_center.y());

return centerMap;

}

//.qml file
Connections {
target: myMap
onCenterChanged: {
myTxt.text = "x " + myMap.center.longitude + " y " + myMap.center.latitude
}
}
@