alternative for QJsonObject::fromVariantMap(data.value<QJSValue().toVariant().toMap())?

Jens van koolwijk

I am trying to send json data between QML and C++ trough signal and slot.I don't want to stringily json.

Now I use this. is there a easier way ?

//qml
signal sendResponse(var data);

//c++
QObject::connect(this->objects[reference], SIGNAL(sendResponse(QVariant)), this, SLOT(parseResponse(QVariant)));

void DisplayInterface::parseResponse(QVariant data)
{
qDebug() << QJsonObject::fromVariantMap(data.value<QJSValue().toVariant().toMap());
}

Paul Colby

Hi @Jens-van-koolwijk,

qDebug() << QJsonObject::fromVariantMap(data.value<QJSValue().toVariant().toMap());

I'm not familiar with QML, nor QJSValue, but just from the docs, I'd start with something like:

qDebug() << data.type() << data.typeName();
qDebug() << data.toJsonObject();
qDebug() << data.toJsonObject().toVariantMap();

What does that output?

Cheers.

Jens van koolwijk

@Paul-Colby

output:
QVariant::QWidget* QJSValue
QJsonObject()
QMap()

Paul Colby

@Jens-van-koolwijk said:

QVariant::QWidget* QJSValue

Ah, so you'll need to use QVariant::toJSValue first, eg:

qDebug() << data.type() << data.typeName();
qDebug() << data.toJsonValue().type() << data.toJsonValue();
qDebug() << data.toJsonValue().toObject();
qDebug() << data.toJsonValue().toObject().toVariantMap();

See if that works.

Jens van koolwijk

@Paul-Colby

output:
QVariant::QWidget* QJSValue
0 QJsonValue(null)
QJsonObject()
QMap()

Hello Paul.

I've read
Qt 5.3 changed the mapping of "var" parameters in QML declared signals to QJSValue. This was reverted
to the behavior of earlier Qt versions to use QVariant. The original issue
of not being able to pass function objects through var parameters of QML
declared signals is solved by wrapping a QJSValue inside the Variant.

So i have to do this
QJsonObject::fromVariantMap(data.value<QJSValue().toVariant().toMap());

But to get json from QML to c++ this looks a little bit ugly to me.