[SOLVED] C++ object as property parameter

kortus

I come with a question to the integration between C++ and QML. I have read the good
"cpp-integration":http://qt-project.org/doc/qt-5.0/qtqml/qtqml-cppintegration-definetypes.html
documentation. But I see no solution for my use case.

The target is to write a module that display properties (in real a lot of properties) of a C++-Object.
At the moment I use the eval() function and it works:-), but I ask if there is a smarter solution. Here my code.

@// MyPropVis.qml
import QtQuick 2.1

Column {
id: propCol
property string objName

Text { text: eval(propCol.objName+".number") }
Text { text: 2 * eval(propCol.objName+".number") }
Text { text: eval(propCol.objName+".number") * eval(propCol.objName+".number") }
}@

@//PropMain.qml
import QtQuick 2.1
import QtQuick.Controls 1.1

Rectangle {
width: 320
height: 200

Row {
spacing: 40

MyPropVis { objName: "prop1" }
MyPropVis { objName: "prop2" }

Button {
text: qsTr("Set 87")
onClicked: { prop1.setnumber(87) }
}
}
}@

@//MyProps.h
#ifndef MYPROPS_H
#define MYPROPS_H

#include <QObject>

class MyProps : public QObject
{
Q_OBJECT

Q_PROPERTY(quint32 number READ getnumber WRITE setnumber NOTIFY numberChanged)
public:
explicit MyProps(quint32 init, QObject *parent = 0);

quint32 getnumber() const { return number; }

signals:
void numberChanged();

public slots:
void setnumber(quint32 localParameter);

private:
quint32 number;
};

#endif // MYPROPS_H@

@//main.cpp
#include "MyProps.h"

#include <QGuiApplication>
#include <QQmlContext>
#include <QQmlEngine>
#include <QQuickView>

int main(int argc, char *argv[])
{
QGuiApplication app(argc, argv);
QQuickView viewer;

MyProps prop1(34);
MyProps prop2(42);

viewer.rootContext()->setContextProperty("prop1", &prop1);
viewer.rootContext()->setContextProperty("prop2", &prop2);
viewer.setSource(QUrl("qrc:/qml/helloQml/PropMain.qml"));
viewer.show();
return app.exec();
}@

Thanks for any hint.

sierdzio

All properties of an object (that derives from QObject) can be read in QML using dot notation.

You do not need to create your special "objName" property: all QML and QObjects have "objectName" property. By default it is empty, but you can choose to set it.

You do not need to pass your objects by string name: QML understands QObject pointers. So, instead of using
@
property string objName
@

you can use:
@
property var objectPointer
@

I think this might help you a bit ;) I've kept the description broad and not detailed because I do not fully understand your use case. Feel free to ask for more info if anything is unclear.

kortus

Yeah, so simple, thanks.

Sometimes it is hard to do the step from a strongly typed language to Javascript/QML:-)