My qml doesn't find my model from python

[le-fab.]

Hello here is a simple test to fill a ListView from ma python main file, I have the following error:
file:/// ..... /main.qml:26: ReferenceError: elements is not defined

here is the qml file

import QtQuick 2.9
import QtQuick.Window 2.2
import QtQuick.Controls 1.4
import PyModels 1.0

Window {
    id: window
    visible: true
    width: 640
    height: 460
    title: qsTr("Test")
    
    Button {
        id: btn
        text: qsTr("fill model")
        onClicked: {
            py_mainapp.fillModel()
        }
    }

    ListView {
            anchors.top: parent.top
            anchors.left: btn.right
            anchors.right: parent.right
            anchors.bottom: parent.bottom
            model: elements.items
            delegate: Item {
                anchors.left: parent.left
                anchors.right: parent.right
                height: 24
                Row {
                    anchors.fill: parent
                    Label {
                        text: model.name
                    }
                    Label {
                        text: model.title
                }
            }
        }
    }     
    
}

Here is the py file

#!/usr/bin/env python
# -*- coding: utf-8 -*-
import sys
import os
from PyQt5.QtWidgets import QApplication
from PyQt5.QtQml import QQmlApplicationEngine, QQmlListProperty, qmlRegisterType
from PyQt5.QtCore import pyqtSlot, QObject, QVariant,pyqtProperty


class ListElementPy(QObject):

    def __init__(self, name, title):
        super(ListElementPy, self).__init__()
        self._title = title
        self._name = name
        
    @pyqtProperty('QString')
    def title(self):
        return self._title

    @title.setter
    def title(self, avalue):
        if avalue != self._title:
            self._title = avalue
                
    @pyqtProperty('QString')
    def name(self):
        return self._name
        
    @name.setter
    def name(self, avalue):
        if avalue != self._name:
            self._name = avalue
                

class ElementsPy(QObject):
    
    def __init__(self):
        super(ElementsPy, self).__init__()
        self._items = []
        
    @pyqtProperty('QString')
    def items(self):
        return QQmlListProperty(ListElementPy, self, self._items)
       
    def append(self, avalue):
        self._items.append(avalue)
                

class MainApp(QObject):

    def __init__(self, context, parent):
        super(MainApp, self).__init__(parent)
        self.win = parent
        self.ctx = context
        self.elements = ElementsPy()
        

    @pyqtSlot()
    def fillModel(self):
        for x in range (1,50):
            self.elements.append(ListElementPy("name %.0f" % (x), "title %.0f" % (x)))
            

if __name__ == "__main__":
    app = QApplication(sys.argv)
    qmlRegisterType(ListElementPy, "PyModels", 1, 0, "ListElementPy")
    qmlRegisterType(ElementsPy, "PyModels", 1, 0, "ElementsPy")
    engine = QQmlApplicationEngine()
    ctx = engine.rootContext()
    engine.load("main.qml")
    win = engine.rootObjects()[0]
    py_mainapp = MainApp(ctx, win)
    ctx.setContextProperty("py_mainapp", py_mainapp)
    ctx.setContextProperty("elements", py_mainapp.elements)
    win.show()
    sys.exit(app.exec_())

What am I doing wrong?
py_mainapp is found in the qml, but not elements

[le-fab.]

I added the following lines in the qml (which seems to me quite strange as I already defined elements in the python file)

ElementsPy {
    id: elements
}
ListElementPy {
    property string name
    property string title
}

Now I have the following error:
TypeError: init() takes 1 positional argument but 2 were given

[le-fab.]

ok, I've found on internet (https://riverbankcomputing.com/pipermail/pyqt/2017-January/038497.html) a solution working, so I'm gonna start with modifying the following code which works:
qml:

import QtQuick 2.9
import QtQuick.Window 2.2
import QtQuick.Controls 1.4

import Example 1.0

Window {
    width: 500
    height: 500
    visible: true

    ListView {
        anchors.fill: parent
        model: store.channels
        delegate: Item {
            anchors.left: parent.left
            anchors.right: parent.right
            height: 24
            Row {
                anchors.fill: parent
                Label {
                    text: name
                }
                Label {
                    text: title
                }
            }
        }
    }
}

python:

from sys import argv
from PyQt5.QtWidgets import QApplication
from PyQt5.QtCore import QObject, QTimer, pyqtProperty, pyqtSignal
from PyQt5.QtQml import QQmlListProperty, QQmlApplicationEngine, qmlRegisterType
                
class Channel(QObject):

    nameChanged = pyqtSignal()
    titleChanged = pyqtSignal()

    def __init__(self, name='', title='', *args, **kwargs):
        super().__init__(*args, **kwargs)
        self._name = name
        self._title = title

    @pyqtProperty('QString', notify=nameChanged)
    def name(self):
        return self._name

    @name.setter
    def name(self, name):
        if name != self._name:
            self._name = name
            self.nameChanged.emit()
            
    @pyqtProperty('QString', notify=nameChanged)
    def title(self):
        return self._title

    @title.setter
    def title(self, title):
        if title != self._title:
            self._title = title
            self.titleChanged.emit()

class Store(QObject):

    channelsChanged = pyqtSignal()

    def __init__(self, *args, **kwargs):
        super().__init__(*args, **kwargs)
        self._channels = [
            Channel('aa', 'AAA'),
            Channel('bb', 'BBB')
        ]

    @pyqtProperty(QQmlListProperty, notify=channelsChanged)
    def channels(self):
        return QQmlListProperty(Channel, self, self._channels)

    @channels.setter
    def channels(self, channels):
        if channels != self._channels:
            self._channels = channels
            self.channelsChanged.emit()

    def appendChannel(self, channel):
        self._channels.append(channel)
        self.channelsChanged.emit()


def main():
    app = QApplication(argv)

    qmlRegisterType(Channel, 'Example', 1, 0, 'Channel')
    qmlRegisterType(Store, 'Example', 1, 0, 'Store')

    store = Store()

    engine = QQmlApplicationEngine()
    engine.rootContext().setContextProperty('store', store)
    engine.load('main.qml')

    # After 3 seconds, we append a new Channel
    QTimer.singleShot(3000, lambda: store.appendChannel(Channel('cc', 'CCC')))

    exit(app.exec_())


if __name__ == '__main__':
    main()

[VRonin]

The problem is in your delegate. The syntax is role.property not modelName.property. See this wiki post (the code is C++ but there's no real difference in python)