Extending QML (advanced) - Grouped Properties#
This is the fourth of a series of 6 examples forming a tutorial using the example of a birthday party to demonstrate some of the advanced features of QML.
More information is needed about the shoes of the guests. Aside from their
size, we also want to store the shoes’ color, brand, and price. This
information is stored in a ShoeDescription class.
14@QmlAnonymous
15class ShoeDescription(QObject):
16 brand_changed = Signal()
17 size_changed = Signal()
18 price_changed = Signal()
19 color_changed = Signal()
20
21 def __init__(self, parent=None):
22 super().__init__(parent)
23 self._brand = ''
24 self._size = 0
25 self._price = 0
26 self._color = QColor()
27
28 @Property(str, notify=brand_changed, final=True)
29 def brand(self):
30 return self._brand
31
32 @brand.setter
33 def brand(self, b):
34 if self._brand != b:
35 self._brand = b
36 self.brand_changed.emit()
37
38 @Property(int, notify=size_changed, final=True)
39 def size(self):
40 return self._size
41
42 @size.setter
43 def size(self, s):
44 if self._size != s:
45 self._size = s
46 self.size_changed.emit()
47
48 @Property(float, notify=price_changed, final=True)
49 def price(self):
50 return self._price
51
52 @price.setter
53 def price(self, p):
54 if self._price != p:
55 self._price = p
56 self.price_changed.emit()
57
58 @Property(QColor, notify=color_changed, final=True)
59 def color(self):
60 return self._color
61
62 @color.setter
63 def color(self, c):
64 if self._color != c:
65 self._color = c
66 self.color_changed.emit()
Each person now has two properties, a name and a shoe description shoe.
69@QmlAnonymous
70class Person(QObject):
71 name_changed = Signal()
72
73 def __init__(self, parent=None):
74 super().__init__(parent)
75 self._name = ''
76 self._shoe = ShoeDescription()
77
78 @Property(str, notify=name_changed, final=True)
79 def name(self):
80 return self._name
81
82 @name.setter
83 def name(self, n):
84 if self._name != n:
85 self._name = n
86 self.name_changed.emit()
87
88 @Property(ShoeDescription, final=True)
89 def shoe(self):
90 return self._shoe
Specifying the values for each element of the shoe description works but is a bit repetitive.
26 Girl {
27 name: "Anne Brown"
28 shoe.size: 7
29 shoe.color: "red"
30 shoe.brand: "Job Macobs"
31 shoe.price: 699.99
32 }
Grouped properties provide a more elegant way of assigning these properties.
Instead of assigning the values to each property one-by-one, the individual
values can be passed as a group to the shoe property making the code more
readable. No changes are required to enable this feature as it is available by
default for all of QML.
9 host: Boy {
10 name: "Bob Jones"
11 shoe { size: 12; color: "white"; brand: "Bikey"; price: 90.0 }
12 }
# Copyright (C) 2022 The Qt Company Ltd.
# SPDX-License-Identifier: LicenseRef-Qt-Commercial OR BSD-3-Clause
"""PySide6 port of the qml/examples/qml/tutorials/extending-qml-advanced/advanced4-Grouped-properties example from Qt v6.x"""
from pathlib import Path
import sys
from PySide6.QtCore import QCoreApplication
from PySide6.QtQml import QQmlComponent, QQmlEngine
from person import Boy, Girl
from birthdayparty import BirthdayParty
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:")
best_shoe = None
for g in range(party.guestCount()):
guest = party.guest(g)
name = guest.name
print(f" {name}")
if not best_shoe or best_shoe.shoe.price < guest.shoe.price:
best_shoe = guest
if best_shoe:
print(f"{best_shoe.name} is wearing the best shoes!")
del engine
sys.exit(0)
# Copyright (C) 2022 The Qt Company Ltd.
# SPDX-License-Identifier: LicenseRef-Qt-Commercial OR BSD-3-Clause
from PySide6.QtCore import QObject, ClassInfo, Property, Signal
from PySide6.QtQml import 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
@QmlElement
@ClassInfo(DefaultProperty="guests")
class BirthdayParty(QObject):
host_changed = Signal()
guests_changed = Signal()
def __init__(self, parent=None):
super().__init__(parent)
self._host = None
self._guests = []
@Property(Person, notify=host_changed, final=True)
def host(self):
return self._host
@host.setter
def host(self, h):
if self._host != h:
self._host = h
self.host_changed.emit()
def guest(self, n):
return self._guests[n]
def guestCount(self):
return len(self._guests)
def appendGuest(self, guest):
self._guests.append(guest)
self.guests_changed.emit()
guests = ListProperty(Person, appendGuest, notify=guests_changed, final=True)
# Copyright (C) 2022 The Qt Company Ltd.
# SPDX-License-Identifier: LicenseRef-Qt-Commercial OR BSD-3-Clause
from PySide6.QtCore import QObject, Property, Signal
from PySide6.QtGui import QColor
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 ShoeDescription(QObject):
brand_changed = Signal()
size_changed = Signal()
price_changed = Signal()
color_changed = Signal()
def __init__(self, parent=None):
super().__init__(parent)
self._brand = ''
self._size = 0
self._price = 0
self._color = QColor()
@Property(str, notify=brand_changed, final=True)
def brand(self):
return self._brand
@brand.setter
def brand(self, b):
if self._brand != b:
self._brand = b
self.brand_changed.emit()
@Property(int, notify=size_changed, final=True)
def size(self):
return self._size
@size.setter
def size(self, s):
if self._size != s:
self._size = s
self.size_changed.emit()
@Property(float, notify=price_changed, final=True)
def price(self):
return self._price
@price.setter
def price(self, p):
if self._price != p:
self._price = p
self.price_changed.emit()
@Property(QColor, notify=color_changed, final=True)
def color(self):
return self._color
@color.setter
def color(self, c):
if self._color != c:
self._color = c
self.color_changed.emit()
@QmlAnonymous
class Person(QObject):
name_changed = Signal()
def __init__(self, parent=None):
super().__init__(parent)
self._name = ''
self._shoe = ShoeDescription()
@Property(str, notify=name_changed, final=True)
def name(self):
return self._name
@name.setter
def name(self, n):
if self._name != n:
self._name = n
self.name_changed.emit()
@Property(ShoeDescription, final=True)
def shoe(self):
return self._shoe
@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 QtQuick
import People
BirthdayParty {
host: Boy {
name: "Bob Jones"
shoe { size: 12; color: "white"; brand: "Bikey"; price: 90.0 }
}
Boy {
name: "Leo Hodges"
shoe { size: 10; color: "black"; brand: "Thebok"; price: 59.95 }
}
Boy { name: "Jack Smith"
shoe {
size: 8
color: "blue"
brand: "Luma"
price: 19.95
}
}
Girl {
name: "Anne Brown"
shoe.size: 7
shoe.color: "red"
shoe.brand: "Job Macobs"
shoe.price: 699.99
}
}
module People
typeinfo coercion.qmltypes
Main 1.0 Main.qml