[PyQt] How to send basic (json-expressible) objects from PyQt up to QML?

[Russell Warren]

... nevermind.  The provided code does actually work perfectly.  I'm an
idiot and didn't recognize the [object Object] notation.

ie: PyQt does a really great job marshalling python types through
QVariant.  Qt then handles QML conversions nicely through this table:
http://doc.qt.io/qt-5/qtqml-cppintegration-data.html#basic-qt-data-types

Sorry for the noise.

Russ


On Wed, Feb 1, 2017 at 10:31 PM, Russell Warren <russ at perspexis.com> wrote:

> Sending basic javascript objects (ie: anything expressible with simple
> json) down to PyQt works fantastically well with the use of
> QJSValue.toVariant(), but I'm having a hard time figuring out how to do
> the reverse.
>
> What is the correct way to send arbitrarily nested, json-expressible,
> objects from PyQt up to QML?
>
> Below is a small example that demonstrates both aspects.  Push the button
> and you can send an arbitrary javascript/json object down to python.  It
> will translate to python perfectly.  The example then tries to send it back
> to QML in a signal argument, but the result isn't quite right.
>
> Here's the console output for the unmodified example (after button push):
>
> Python received: [{'foo': 'bar', 'baz': 1}, [1, 2, 3]]
> Emitting signal...
> qml: QML received: [object Object],1,2,3
>
> Ideally, QML should receive the same thing!
>
> I have tried some variations of QJSValue and QVariant with no success.
> What is the correct way to do this?
>
> Here is the complete example:
>
> #!/usr/bin/env python
> import sys
> from PyQt5 import QtCore, QtQml, QtQml, QtWidgets
>
> QML = '''
> import QtQuick 2.5
> import QtQuick.Window 2.2
> import QtQuick.Controls 1.4
> import SignalTesting 1.0
>
> Window {
>     id: base
>     visible: true
>     width: 300
>     height: 100
>
>     SignalTester {
>         id: st
>         onTestSignal: console.log("QML received: " + testVal)
>     }
>     Column {
>         TextInput {
>             id: txtEval
>             text: "[{foo: 'bar', baz: 1}, [1,2,3]]"
>         }
>         Button {
>             text: "sendSignal"
>             onClicked: st.sendSignal(eval(txtEval.text))
>         }
>     }
> }
> '''
>
> class SignalTester(QtCore.QObject):
>     testSignal = QtCore.pyqtSignal(QtCore.QVariant, arguments =
> ["testVal"])
>
>     @QtCore.pyqtSlot(QtQml.QJSValue)
>     def sendSignal(self, v):
>         v = v.toVariant()
>         print("Python received: %r" % v)
>         print("Emitting signal...")
>         self.testSignal.emit(v)
>
>
> if __name__ == '__main__':
>     qmlPath = "SignalTester.qml"
>     with open(qmlPath, "w") as fp:
>         fp.write(QML)
>     app = QtWidgets.QApplication(sys.argv + ["-nograb"])
>     QtQml.qmlRegisterType(SignalTester, "SignalTesting", 1, 0,
> "SignalTester")
>     engine = QtQml.QQmlApplicationEngine(qmlPath)
>     sys.exit(app.exec_())
>
>
>
>


-- 
Russell Warren
Perspexis Technologies Inc.

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