Extending QML - Attached Properties Example

This example builds on the Extending QML - Default Property Example, Extending QML - Inheritance and Coercion Example, Extending QML - Object and List Property Types Example and the Extending QML - Adding Types Example.

The Attached Properties Example example shows how to inject properties to child objects.

main.py

# Copyright (C) 2022 The Qt Company Ltd.
# SPDX-License-Identifier: LicenseRef-Qt-Commercial OR BSD-3-Clause

"""PySide6 port of the qml/examples/qml/referenceexamples/attached example from Qt v6.x"""

from pathlib import Path
import sys

from PySide6.QtCore import QCoreApplication, QUrl
from PySide6.QtQml import QQmlComponent, QQmlEngine, qmlAttachedPropertiesObject

from person import Boy, Girl
from birthdayparty import BirthdayParty


app = QCoreApplication(sys.argv)
qml_file = Path(__file__).parent / "example.qml"
url = QUrl.fromLocalFile(qml_file)
engine = QQmlEngine()
component = QQmlComponent(engine, url)
party = component.create()
if not party:
    print(component.errors())
    del engine
    sys.exit(-1)
host = party.host
print(f"{host.name} is having a birthday!")
if isinstance(host, Boy):
    print("He is inviting:")
else:
    print("She is inviting:")
for g in range(party.guestCount()):
    guest = party.guest(g)
    name = guest.name

    rsvp_date = None
    attached = qmlAttachedPropertiesObject(BirthdayParty, guest, False)
    if attached:
        rsvp_date = attached.rsvp.toString()
    if rsvp_date:
        print(f"    {name} RSVP date: {rsvp_date}")
    else:
        print(f"    {name} RSVP date: Hasn't RSVP'd")

del engine
sys.exit(0)

birthdayparty.py

# Copyright (C) 2022 The Qt Company Ltd.
# SPDX-License-Identifier: LicenseRef-Qt-Commercial OR BSD-3-Clause

from PySide6.QtCore import QDate, QObject, ClassInfo, Property
from PySide6.QtQml import QmlAnonymous, QmlAttached, QmlElement, ListProperty

from person import Person


# To be used on the @QmlElement decorator
# (QML_IMPORT_MINOR_VERSION is optional)
QML_IMPORT_NAME = "examples.default.people"
QML_IMPORT_MAJOR_VERSION = 1


@QmlAnonymous
class BirthdayPartyAttached(QObject):

    def __init__(self, parent=None):
        super().__init__(parent)
        self._rsvp = QDate()

    @Property(QDate)
    def rsvp(self):
        return self._rsvp

    @rsvp.setter
    def rsvp(self, d):
        self._rsvp = d


@QmlElement
@ClassInfo(DefaultProperty="guests")
@QmlAttached(BirthdayPartyAttached)
class BirthdayParty(QObject):

    def __init__(self, parent=None):
        super().__init__(parent)
        self._host = None
        self._guests = []

    @Property(Person)
    def host(self):
        return self._host

    @host.setter
    def host(self, h):
        self._host = h

    def guest(self, n):
        return self._guests[n]

    def guestCount(self):
        return len(self._guests)

    def appendGuest(self, guest):
        self._guests.append(guest)

    @staticmethod
    def qmlAttachedProperties(self, o):
        return BirthdayPartyAttached(o)

    guests = ListProperty(Person, appendGuest)

person.py

# Copyright (C) 2022 The Qt Company Ltd.
# SPDX-License-Identifier: LicenseRef-Qt-Commercial OR BSD-3-Clause

from PySide6.QtCore import QObject, Property
from PySide6.QtQml import QmlAnonymous, QmlElement

# To be used on the @QmlElement decorator
# (QML_IMPORT_MINOR_VERSION is optional)
QML_IMPORT_NAME = "examples.default.people"
QML_IMPORT_MAJOR_VERSION = 1


@QmlAnonymous
class Person(QObject):
    def __init__(self, parent=None):
        super().__init__(parent)
        self._name = ''
        self._shoe_size = 0

    @Property(str)
    def name(self):
        return self._name

    @name.setter
    def name(self, n):
        self._name = n

    @Property(int)
    def shoe_size(self):
        return self._shoe_size

    @shoe_size.setter
    def shoe_size(self, s):
        self._shoe_size = s


@QmlElement
class Boy(Person):
    def __init__(self, parent=None):
        super().__init__(parent)


@QmlElement
class Girl(Person):
    def __init__(self, parent=None):
        super().__init__(parent)

example.qml

// Copyright (C) 2022 The Qt Company Ltd.
// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR BSD-3-Clause

import examples.default.people

BirthdayParty {
    Boy {
        name: "Robert Campbell"
        BirthdayParty.rsvp: "2009-07-01"
    }

    Boy {
        name: "Leo Hodges"
        shoe_size: 10
        BirthdayParty.rsvp: "2009-07-06"
    }

    host: Boy {
        name: "Jack Smith"
        shoe_size: 8
    }
}