没有黑客就无法在PySide2上使用QAbstractListModel子类

Question

Using the work-in-progress PySide2 (to be able to use Qt5), I have the following code:

main.qml:

import QtQuick 2.0
import QtQuick.Controls 1.3

ApplicationWindow {
    visible: true
    ListView {
        width: 100
        height: 100
        model: listModel
        delegate: Text {
            text: model.name
        }
    }
}

main.py:

from sys import argv, exit

from PySide2.QtCore import QAbstractListModel
from PySide2.QtGui import QGuiApplication
from PySide2.QtQml import QQmlApplicationEngine


class TaskListModel(QAbstractListModel):

    _COLUMNS = ('name',)

    def data(self, index, role):
        if role == self._COLUMNS.index('name'):
            return str(index.row())
        return None

    def roleNames(self):
        return dict(enumerate(self._COLUMNS))

    def rowCount(self, parent):
        return 1


app = QGuiApplication(argv)
engine = QQmlApplicationEngine()
engine.rootContext().setContextProperty('listModel', None)
engine.load('main.qml')
engine.rootContext().setContextProperty('listModel', TaskListModel())
exit(app.exec_())

The 3 method calls on the engine object towards the end of main.py are the way they are because:

1. I get Unable to assign [undefined] to QString if I use:

    engine.rootContext().setContextProperty('listModel', TaskListModel()) engine.load('main.qml') 

2. I get ReferenceError: listModel is not defined if I use:

    engine.load('main.qml') engine.rootContext().setContextProperty('listModel', TaskListModel()) 

Is my way the only way to do this properly? Shouldn't the code in my first bullet above work as well?

Answer 1

It seems that PySide2 removes TaskListModel() from memory if you assign it to some variable, I have found 2 solutions:

• Create a variable that stores the model:

---

app = QGuiApplication(argv)
engine = QQmlApplicationEngine()
model = TaskListModel()
engine.rootContext().setContextProperty('listModel', model)
engine.load('main.qml')
exit(app.exec_())

• Pass a parent to the model:

---

app = QGuiApplication(argv)
engine = QQmlApplicationEngine()
engine.rootContext().setContextProperty('listModel', TaskListModel(engine))
engine.load('main.qml')
exit(app.exec_())