QDBusInterface interface( "de.pengutronix.rauc",

                    "/",

                    "de.pengutronix.rauc.Installer",

                    QDBusConnection::systemBus() );

QVariant property = interface.property("Progress");

property.value<QDBusArgument>() >> parameterProgress;

No I get a compiler error:

no match for operator>>'(opernad types are 'QDBusArgument' and 'MyProgress')

I think I do the registration an the installing of the oparators wrong.

The registration is done in the constructor of MyProgress:

MyProgress ::MyProgress(){

    qRegisterMetaType<MyProgress>();
    qDBusRegisterMetaType<MyProgress>();
}

The magic statement I place in top of my MyProcess.cpp

// this is one of the magic statements
Q_DECLARE_METATYPE(MyProgress)

But where exactly do you place the operators? Also in the MyProcess.cpp?

It seems like I am only a few millimeters away from my goal.

Thanks

Von: Eugen.Wiens@JUMO.net <Eugen.Wiens@JUMO.net>
Gesendet: Montag, 2. August 2021 13:41
An: Stahl, Michael <mstahl@moba.de>
Cc: RAUC@pengutronix.de <RAUC@pengutronix.de>
Betreff: Antwort: [RAUC] D-Bus control Qt

Hi Michael,

"RAUC" <rauc-bounces@pengutronix.de> schrieb am 02.08.2021 08:15:26: > Von: "Stahl, Michael" <mstahl@moba.de>
> An: "RAUC@pengutronix.de" <RAUC@pengutronix.de>
> Datum: 02.08.2021 08:15
> Betreff: [RAUC] D-Bus control Qt
> Gesendet von: "RAUC" <rauc-bounces@pengutronix.de>
> > Is there someone who implemented the DBus Property "Progress" into a > Qt-Application? The problem seems the return value isi (Integer, > String, Integer).
> For all other properties with a single return value like "Operation" > or "LastError" the Qt DBus API works fine.
> I found an email from 28.Oct 2019 in the mailing list where Bastian > Krause had the same issue. The answer was only that he had to > cunsult the Qt DBus documentation on how a tuple is mapped to Qt types.
> > Thats a good hint but after hours of searching the web I didn't find > a solution. The return value for a property is QVariant in Qt.
> > Trial 1 -> Read value by iface.property("Progress"):
> This is the error message I got when I try to read the progress property:
> Cannot construct placeholder type QDBusRawType
> > Trial 2 -> Read value by iface.call("Get",...):
> Not able to get any information. The arguments of the returned > QDBusMessages are always empty!
That is the way we implemented it:

On Qt there are some pitfalls and you has to marshaling the data.

1. Create a Data Class

#include <QObject>
#include <QDBusArgument>
#include <QString>

class MyProgress
{
public:
[...]
int m_Progress;
QString m_Message;
int m_Additional;
};

// this is one of the magic statements
Q_DECLARE_METATYPE(MyProgress)
QDBusArgument &operator<<(QDBusArgument &argument, const MyProgress& parameterProgress);
const QDBusArgument &operator>>(const QDBusArgument &argument, MyProgress& parameterProgress);
};

You has to register the metatype and implement the operators. In the Constructor you has to add two register Methods

qRegisterMetaType<MyProgress>();
qDBusRegisterMetaType<MyProgress>();

After this tree registrations your Class MyProgress is known by Qt Metatype System. Now you has to implement operators

QDBusArgument &operator<<(QDBusArgument &argument, const MyProgress& parameterProgress)
{
argument.beginStructure();
argument << parameterProgress.m_Progress;
argument << parameterProgress.m_Message;
argument << parameterProgress.m_Additional;
argument.endStructure();
return argument;
}
const QDBusArgument &operator>>(const QDBusArgument &argument, MyProgress& parameterProgress)
{
argument.beginStructure();
argument >> parameterProgress.m_Progress;
argument >> parameterProgress.m_Message;
argument >> parameterProgress.m_Additional;
argument.endStructure();
return argument;
}

Now you are finished with preparing how to use it. In the Qt Slot of the D-Bus call your can pipe it in your class

MyProgress parameterProgress;
property.value<QDBusArgument>() >> parameterProgress;

This URL help you to map our code to the Qt example https://doc.qt.io/qt-5/qdbusargument.html

I hope it helps

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