Extending QML - Binding Example

This example builds on the Extending QML - Adding Types Example, the Extending QML (advanced) - Attached Properties, the Extending QML (advanced) - Default Properties, the Extending QML (advanced) - Inheritance and Coercion the Extending QML - Object and List Property Types Example and the Extending QML (advanced) - Property Value Source.

Running the Example

The main.py file in the example includes a simple shell application that loads and runs the QML snippet shown below.

Download this example

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

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

from pathlib import Path
import sys

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

from person import Boy, Girl  # noqa: F401
from birthdayparty import BirthdayParty  # noqa: F401
from happybirthdaysong import HappyBirthdaySong  # noqa: F401


if __name__ == "__main__":
    app = QCoreApplication(sys.argv)
    engine = QQmlEngine()
    engine.addImportPath(Path(__file__).parent)
    component = QQmlComponent(engine)
    component.loadFromModule("People", "Main")
    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")

    party.startParty()

    r = app.exec()

    del engine
    sys.exit(r)
# Copyright (C) 2022 The Qt Company Ltd.
# SPDX-License-Identifier: LicenseRef-Qt-Commercial OR BSD-3-Clause
from __future__ import annotations

from PySide6.QtCore import QDate, QObject, ClassInfo, Property, QTime, Signal
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 = "People"
QML_IMPORT_MAJOR_VERSION = 1


@QmlAnonymous
class BirthdayPartyAttached(QObject):

    rsvp_changed = Signal()

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

    @Property(QDate, notify=rsvp_changed)
    def rsvp(self):
        return self._rsvp

    @rsvp.setter
    def rsvp(self, d):
        if self._rsvp != d:
            self._rsvp = d
            self.rsvp_changed.emit()


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

    partyStarted = Signal(QTime)
    host_changed = Signal()

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

    def startParty(self):
        self.partyStarted.emit(QTime.currentTime())

    @Property(Person, notify=host_changed)
    def host(self):
        return self._host

    @host.setter
    def host(self, h):
        if self._host != h:
            self._host = h
            self.host_changed.emit()

    @Property(str)
    def announcement(self):
        return ""

    @announcement.setter
    def announcement(self, a):
        print(a)

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

from PySide6.QtCore import QTimer, Property, Slot
from PySide6.QtQml import QmlElement, QPyQmlPropertyValueSource

# To be used on the @QmlElement decorator
# (QML_IMPORT_MINOR_VERSION is optional)
QML_IMPORT_NAME = "People"
QML_IMPORT_MAJOR_VERSION = 1


@QmlElement
class HappyBirthdaySong(QPyQmlPropertyValueSource):

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

        self.m_target = None
        self.m_name = ""
        self.m_line = -1
        self.m_lyrics = []

        self.m_timer = QTimer(self)
        self.m_timer.timeout.connect(self.advance)
        self.m_timer.start(1000)

    def setTarget(self, property):
        self.m_target = property

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

    @name.setter
    def name(self, n):
        self.m_name = n
        self.m_lyrics = ["Happy birthday to you,",
                         "Happy birthday to you,",
                         f"Happy birthday dear {self.m_name},",
                         "Happy birthday to you!",
                         ""]

    @Slot()
    def advance(self):
        self.m_line = (self.m_line + 1) % len(self.m_lyrics)
        self.m_target.write(self.m_lyrics[self.m_line])
# Copyright (C) 2022 The Qt Company Ltd.
# SPDX-License-Identifier: LicenseRef-Qt-Commercial OR BSD-3-Clause
from __future__ import annotations

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

# To be used on the @QmlElement decorator
# (QML_IMPORT_MINOR_VERSION is optional)
QML_IMPORT_NAME = "People"
QML_IMPORT_MAJOR_VERSION = 1


@QmlAnonymous
class Person(QObject):
    name_changed = Signal()
    shoe_size_changed = Signal()

    def __init__(self, parent=None):
        super().__init__(parent)
        self._name = ''
        self._shoe_size = 0

    @Property(str, notify=name_changed)
    def name(self):
        return self._name

    @name.setter
    def name(self, n):
        if self._name != n:
            self._name = n
            self.name_changed.emit()

    @Property(int, notify=shoe_size_changed)
    def shoe_size(self):
        return self._shoe_size

    @shoe_size.setter
    def shoe_size(self, s):
        if self._shoe_size != s:
            self._shoe_size = s
            self.shoe_size_changed.emit()


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


@QmlElement
class Girl(Person):
    def __init__(self, parent=None):
        super().__init__(parent)
// Copyright (C) 2022 The Qt Company Ltd.
// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR BSD-3-Clause

import People

BirthdayParty {
    id: theParty

    HappyBirthdaySong on announcement { name: theParty.host.name }

    onPartyStarted: (time) => { console.log("This party started rockin' at " + time); }

    host: Boy {
        name: "Bob Jones"
        shoe_size: 12
    }

    Boy {
        name: "Leo Hodges"
        BirthdayParty.rsvp: "2009-07-06"
    }
    Boy {
        name: "Jack Smith"
    }
    Girl {
        name: "Anne Brown"
        BirthdayParty.rsvp: "2009-07-01"
    }
}
module People
typeinfo coercion.qmltypes
Main 1.0 Main.qml