Signal from Qt to Qml function not working when using parameters...

[Palooka]

Hi,

Been searching around for an explanation to this problem, but no luck. Any help appreciated

I want to send a signal from my c++ class to a qml function/slot

If I do it without using any parameters it works nicely, like this:
connect(this, SIGNAL(temp()), m_parent, SLOT(settemp()));

But when adding parameters of type int it fails with the "No such slot" error, like this:
connect(this, SIGNAL(valueChanged(int)), m_parent, SLOT(setslider(int)));

Please study the code below and help a Qt newb ...

//! [imports]
import QtQuick 1.0
import "content"
//! [imports]
 
//! [0]
Rectangle {
    color: "#545454"
    width: 300; height: 300
 
    // Signals
    signal sliderX(int X)
 
    // Slots
    function settemp(){ dial.value = 50; }
    function setslider(value){ dial.value = value; }
 
    Dial {
        id: dial
        anchors.centerIn: parent
        value: 10
    }
}
//! [0]

//! [imports]
import QtQuick 1.0
import "content"
//! [imports]

//! [0]
Rectangle {
    color: "#545454"
    width: 300; height: 300

    // Signals
    signal sliderX(int X)

    // Slots
    function settemp(){ dial.value = 50; }
    function setslider(value){ dial.value = value; }

    Dial {
        id: dial
        anchors.centerIn: parent
        value: 10
    }
}
//! [0]

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#ifndef MYTEST_H
#define MYTEST_H
 
#include <QObject>
 
class myTest: public QObject
{
    Q_OBJECT
 
public:
    myTest(QObject *parent) : QObject(parent) 
    {
        m_value     = 0;
        m_parent    = parent;
        connect(m_parent, SIGNAL(sliderX(int)), this, SLOT(setValue(int)));
 
        connect(this, SIGNAL(temp()), m_parent, SLOT(settemp()));
        connect(this, SIGNAL(valueChanged(int)), m_parent, SLOT(setslider(int)));
 
	emit temp();
        emit valueChanged(100);
    }
    int value() const { return m_value; }
 
public slots:
    void setValue(int value)
    {
        if (value != m_value)
        {
            m_value = value;
            emit valueChanged(value);
        }
    }
signals:
    void valueChanged(int newValue);
    void temp();
 
private:
    int m_value;
    QObject *m_parent;
};
 
#endif // MYTEST_H

#ifndef MYTEST_H
#define MYTEST_H

#include <QObject>

class myTest: public QObject
{
    Q_OBJECT

public:
    myTest(QObject *parent) : QObject(parent) 
    {
        m_value     = 0;
        m_parent    = parent;
        connect(m_parent, SIGNAL(sliderX(int)), this, SLOT(setValue(int)));
        
        connect(this, SIGNAL(temp()), m_parent, SLOT(settemp()));
        connect(this, SIGNAL(valueChanged(int)), m_parent, SLOT(setslider(int)));
        
	emit temp();
        emit valueChanged(100);
    }
    int value() const { return m_value; }

public slots:
    void setValue(int value)
    {
        if (value != m_value)
        {
            m_value = value;
            emit valueChanged(value);
        }
    }
signals:
    void valueChanged(int newValue);
    void temp();

private:
    int m_value;
    QObject *m_parent;
};

#endif // MYTEST_H

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#include <QApplication>
#include <QWidget>
#include <QtGui>
#include <QtDeclarative/QDeclarativeView>
#include <QtDeclarative/QDeclarativeContext>
#include "myTest.h"
 
 
 
int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
 
    QDeclarativeView view;
 
    view.setSource(QUrl::fromLocalFile("../test2/qml/dialcontrol.qml"));
 
    QObject *object = view.rootObject();
 
    QDeclarativeContext *context = view.rootContext();
 
    myTest test(object);
 
    (*context).setContextProperty("myTest", &test);
 
    view.show();
 
    return a.exec();
}

#include <QApplication>
#include <QWidget>
#include <QtGui>
#include <QtDeclarative/QDeclarativeView>
#include <QtDeclarative/QDeclarativeContext>
#include "myTest.h"



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

    QDeclarativeView view;

    view.setSource(QUrl::fromLocalFile("../test2/qml/dialcontrol.qml"));

    QObject *object = view.rootObject();

    QDeclarativeContext *context = view.rootContext();

    myTest test(object);

    (*context).setContextProperty("myTest", &test);

    view.show();

    return a.exec();
}

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[MarekR22]

Take a look on setslider slot method! Does parameter have a type? No since it is java script. So what kind of parameter type should be in C++ code? int? I don't think so. I would try to use QVaraint as slot parameter type (and correct signal too).

[Palooka]

Seems to work nicely, thanks.

If it would help anyone else in the future I changed these lines:

#include <QVariant>
...
connect(this, SIGNAL(valueChanged(QVariant)), m_parent, SLOT(setslider(QVariant)));
...
signals:
    void valueChanged(QVariant newValue);
...

#include <QVariant>
...
connect(this, SIGNAL(valueChanged(QVariant)), m_parent, SLOT(setslider(QVariant)));
...
signals:
    void valueChanged(QVariant newValue);
...

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[Harry443]

Hello Palooka,

Can u please explain the code? I mean about the QDeclarativeContext and the pointer variables?
How exactly the functioning is happennig?
thanx in advance

[JandunCN]

That's the point.