I am a newbie in using Qt framework. I am not sure where I am going wrong. I tried looking at many related material but still could not figure it out.
I am getting "QObject::connect: No such signal error.." while I have declared a signal in a qml file.
Here is the code:
int main(int argc, char *argv[])
{
QApplication app(argc, argv);
//QDeclarativeView view;
QQmlApplicationEngine engine;
testclass dsc;
QQmlComponent component(&engine, QUrl(QStringLiteral("qrc:///test.qml")));
while(component.isLoading());
if (component.isError()) {
qWarning() << component.errors();
}
QObject *object = component.create();
QQuickItem *item = qobject_cast<QQuickItem*>(object);
QObject::connect(item,SIGNAL(dsa(QVariant)),&dsc,SLOT(testslot(QVariant)));
QObject::connect(&dsc,SIGNAL(dummysignal(QVariant)),&dsc,SLOT(testslot(QVariant)));
dsc.dummysignal(&dsc);
qDebug("Entered :");
engine.load(QUrl(QStringLiteral("qrc:///main.qml")));
return app.exec();
}
qml file: test.qml
Item {
width: 800
height: 500
signal dsa(var obj)
SystemPalette { id: palette }
}
Test class: testclass.cpp
#include <QObject>
class testclass: public QObject
{
Q_OBJECT
public:
explicit testclass(QObject *parent = 0);
signals:
void dummysignal(QVariant);
public slots:
void testslot(QVariant);
};
I am getting this error:
QObject::connect: No such signal test_QMLTYPE_0::dsa(QVariant) in ..
The problem is that you're declaring the dsa signal parameter as a 'var' type, which is considered a javascript value by the qml engine. So this gets propagated into c++ as a QJSValue, and the signature of the signal you're trying to connect with is actually dsa(QJSValue).
If you want the signature to be dsa(QVariant), change your signal declaration in test.qml as follows:
// test.qml
Item {
signal dsa(variant obj)
width: 800
height: 500
SystemPalette { id: palette }
}
This should allow you to connect as you were trying with the statement
QObject::connect(item,SIGNAL(dsa(QVariant)),&dsc,SLOT(testslot(QVariant)));
(But first you should update the signature of your slot to void testslot(QVariant);...otherwise you'll just have the same problem on the flip side with a 'no such slot' error)
FWIW, here's a useful trick for debugging 'no such signal/slot' errors:
// Assuming you've instantiated QQuickItem* item
// This will print out the signature for every signal/slot on the object
// Make sure you include <QMetaObject>, <QMetaMethod>
const QMetaObject* metaObj = item->metaObject();
for (int i = 0; i < metaObj->methodCount(); ++i) {
QMetaMethod method = metaObj->method(i);
qDebug() << method.methodSignature();
}
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