Casting signaled QObjects from C++ code

coderbob

I have noticed that QML behaves differently when these objects are passed to the script as a signal. I have added to the previous code example that reproduces this.

The update adds a singleShot QTimer that passed the object1 twice to the script. Once declared class and the second as a QObject.

When passed as a class it is casted as a QVariant and I will not have access to any properties or slots.

When passed as a QObject I will have access to properties but is also casted differently then when it is passed using the doSomething() function. (Clicking anywhere in the window)

I could not find anyway to cast it from a QVariant in the script so I could access it properly. Also a little confused why it is casting the same object type differently.

mbrasser

Would it be possible to include the code inline here (assuming it isn't too long)?

Thanks,
Michael

coderbob

main.cpp
@
#include <QApplication>

#include <qdeclarative.h>
#include <QDeclarativeView>
#include <qdeclarativecontext.h>

#include "object1.h"
#include "object2.h"

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

QDeclarativeView view;
view.setResizeMode(QDeclarativeView::SizeRootObjectToView);

qmlRegisterType<Object1>("com.test.object1", 1, 0, "Object1");
qmlRegisterType<Object2>("com.test.object2", 1, 0, "Object2");

Object1 *object1 = new Object1();

view.rootContext()->setContextProperty("myObject1",object1);

view.setSource(QUrl::fromLocalFile("main.qml"));
view.show();

return app.exec();
}
@

main.js
@
function doConnect()
{
myObject1.mySignalSpecific.connect(displayObject)
myObject1.mySignalQObject.connect(displayObject)
}

function doSomething()
{
var failedObject = myObject1.getObject2();
print(failedObject);
}

function displayObject(obj1)
{
print(obj1);
print(obj1.name);
}
@

main.qml
@
import Qt 4.7

import "main.js" as MainJS

Rectangle {
id: mainWindow

width: 640; height: 480
color: "lightgray"

MouseArea
{
id: mouseArea
anchors.fill: parent
onClicked:
{
MainJS.doSomething();
}
}

Component { Item {} }

Component.onCompleted: MainJS.doConnect();
}
@

object1.h
@
#ifndef OBJECT1_H
#define OBJECT1_H

#include <QObject>

#include "object2.h"

class Object1 : public QObject
{
Q_OBJECT

Q_PROPERTY (QString name READ getName)

public:
Object1(QObject *parent = 0);

public slots:
Object2 *getObject2();
void passObject2Script();

signals:
void mySignalSpecific(Object1 *obj);
void mySignalQObject(QObject *obj);

private:
QString m_name;

QString getName();

};

#endif
@

object1.cpp
@
#include "object1.h"

#include "QTimer"

Object1::Object1(QObject *parent) : QObject(parent)
{
QTimer::singleShot(1000,this,SLOT(passObject2Script()));
m_name = "object1 name property";
}

Object2* Object1::getObject2()
{
return new Object2();
}

void Object1::passObject2Script()
{
emit mySignalSpecific(this);
emit mySignalQObject(this);
}

QString Object1::getName()
{
return m_name;
}
@

object2.h
@
#ifndef OBJECT2_H
#define OBJECT2_H

#include <QObject>
#include <qdeclarative.h>

class Object2 : public QObject
{
Q_OBJECT

Q_PROPERTY (QString name READ getName)

public:
Object2(QObject *parent = 0);

private:
QString m_name;

QString getName();

};

#endif
@

object2.cpp
@
#include "object2.h"

Object2::Object2(QObject *parent) : QObject(parent)
{
m_name = "object2 name property";
}

QString Object2::getName()
{
return m_name;
}
@

Console will show the output, click anywhere on the screen for the object passed directly to the view.

mbrasser

What version of Qt are you using? This sounds very similar to "QTBUG-13047":http://bugreports.qt.nokia.com/browse/QTBUG-13047, which should be fixed in 4.7.1.

Regards,
Michael

coderbob

Same result on 4.7.0 and 4.7.1. From the looks of that bug report it is a different problem What I am seeing is a different cast result depending on how the signal passes the same object.

mbrasser

Okay, I'd suggest adding a new bug report then -- mySignalSpecific and mySignalQObject should be giving the same results.

Regards,
Michael

imxiangpeng

Some days ago, I tried to write some codes like you. It does not work very well. I find that it's wrong in this way.
if you call :
qmlRegisterType<Object1>("com.test.object1", 1, 0, "Object1");
then you can use Object1 in qml file as Rectangle , Image, Text and so on, Object1 is only a type before you use it in qml. such as Object1{id:object_1}
The following code, you write:
Object1 *object1 = new Object1();
view.rootContext()->setContextProperty("myObject1",object1);
works good, but if you call the method of object1, the method must be Q_INVOKABLE