QQmlPropertyMap as return type

topse

Hi,
I want wo exchange dynamic data between C++ and QML (again...). My idea is: I create a C++-Class derived from QQmlPropertyMap. Then in C++ I create lists from that kind of object and I register an QObject to QML, which has a function that can return those objects:

C++:

  broker = new DataBroker(...);
  engine->rootContext()->setContextProperty("broker", broker);

QML:

      // broker.loadQml return a QQmlPropertyMap *
      // does not matter if casted to QObject*
      // it does not work to access or modify properties
      data = broker.loadQml("1234");

When using QQmlPropertyMap as return type of the function, it even gives an error: "Unknown method return type: QQmlPropertyMap*"
When usign QObject* as return type (that means cast the QQmlPropertyMap* to QObject*) it does not give an error, but properties are not accessible to QML.

Can anyone give a hint?

Thanks and best regards,
Tobias

dheerendra

May be you missed registering the meta type as QQmlPropertyMap is not a standard type.

C++ code

qRegisterMetaType<QQmlPropertyMap*>("QQmlPropertyMap");

QQmlPropertyMap* MyAuth::getValues()
{
    QQmlPropertyMap *ownerData = new QQmlPropertyMap;
    ownerData->insert("name", QVariant(QString("Dheerendra")));
    ownerData->insert("email", QVariant(QString("dheerendra@pthinks.com")));
    return ownerData;
}

QML Code

                  var obj = login.getValues();
                  console.log("**** =",obj.name)
                  console.log("**** =",obj.email)

topse

@dheerendra said in QQmlPropertyMap as return type:

qRegisterMetaType<QQmlPropertyMap*>("QQmlPropertyMap");

Jepp... when registering the Meta-Type then at least the error goes away, but the properties are still inaccessible :-/

Best Regards,
Tobias

dheerendra

Please do the code as suggested by me. Otherwise you can share complete code snippet. We will help you.

topse

I did.

My feeling is, the problem is in qv4objectwrapper.cpp, in function CallArgument::initAsType. I think, using QQmlPropertyMap is only valid if set as context property (and not as return type of a function)?

Best Regards,
Tobias

GrecKo

Can you share a reproducible minimal example?

I have no problems using QQmlPropertyMap* as a return type in my projects.
Make sure to qmlRegisterType QQmlPropertyMap, not QQmlPropertyMap*.

topse

main:

int main(int argc, char *argv[])
{
  qRegisterMetaType<QQmlPropertyMap*>("QQmlPropertyMap");
  qmlRegisterType<QQmlPropertyMap>();
  TestQmlJsonConnect::exec(argc, argv);

  return 0;
}

void TestQmlJsonConnect::exec(int argc, char *argv[])
{
  broker = new DataBroker(provider, "JsonData");
  Setup setup;
  quick_test_main_with_setup(argc, argv, "TestQmlJsonConnect", ":/qml", &setup);
  delete broker;
  delete provider;
}
void Setup::qmlEngineAvailable(QQmlEngine *engine)
{
  engine->rootContext()->setContextProperty("broker", broker);
}

QQmlPropertyMap *DataBroker::loadQml(const QUuid &uuid)
{
  QQmlPropertyMap *p = new QQmlPropertyMap();
  p->insert("info", "test");
  return p;
}

import QtQuick 2.12
import QtTest 1.12

TestCase {
    name: "tst_QmlJsonConnect.qml"

    function test_one() {
      data = broker.loadQml("1234");
      console.log(data);              // qml: [object Object]
      console.log(data.info);         // qml: undefined
      compare(data.info, "test");     // compare fails -> test ends
      data.info = "Hallo";
      compare(data.info, "Hallo");
    }
}

:-/

IntruderExcluder

Cannot build your example rn, but have you ever tried to print 'data' keys? Like console.log(Object.keys(data)).

topse

@IntruderExcluder

You are right... I did a really small Application (about 3 lines of code :-)) and there it works. I am going to check, what is wrong with my real "Application" -> This is currently only a Testapplication (using testlib and testcases). Maybe the environment is different there...

Thanks for help,
Tobias

topse

@topse

Found the bug:

var data = broker.loadQml(...);

Forget the var :-(

Thanks for help - it was very appreciated to read, that in principle using QQmlPropertyMap as return type works.

Best Regards,
Tobias