扩展 QML - 对象和列表属性类型示例

导出 C++ 属性。

此示例基于 扩展 QML - 添加类型示例。

对象和列表属性类型示例显示了如何在 QML 中添加对象和列表属性。此示例添加了一个 BirthdayParty 类型，用于指定生日派对，包括庆祝者和宾客列表。人们使用在之前示例中构建的 People QML 类型进行指定。

import examples.properties.people

BirthdayParty {
    host: Person {
        name: "Bob Jones"
        shoe_size: 12
    }
    guests: [
        Person { name: "Leo Hodges" },
        Person { name: "Jack Smith" },
        Person { name: "Anne Brown" }
    ]
}

声明 BirthdayParty

BirthdayParty 类的声明如下

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
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)

    guests = ListProperty(Person, appendGuest)

该类包含一个用于存储庆祝者对象的成员，还有一个用于存储 Person 实例的列表成员。

在QML中，列表属性的类型，包括嘉宾属性（其类型为人物列表），都是ListProperty类型。ListProperty是一种简单的数据类型，包含了若干函数。当QML需要从列表中读取、写入或与之交互时，会调用这些函数。除了具体的列表，如示例中使用的“人物列表”外，QQmlListProperty的使用还允许实现“虚拟列表”和其他高级场景。

运行示例

示例中的main.py文件包含一个简单的Shell应用程序，用于加载并运行本页开头所显示的QML片段。

下载 此示例

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/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 Person  # noqa: F401
from birthdayparty import BirthdayParty  # 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 party:
        print(f"{party.host} is having a birthday!\nThey are inviting:")
        for g in range(party.guestCount()):
            name = party.guest(g).name
            print(f"    {name}")
    else:
        print(component.errors())

    del engine
    sys.exit(0)

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 QmlElement

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


@QmlElement
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

birthdayparty.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 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
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)

    guests = ListProperty(Person, appendGuest)

People/Main.qml

// Copyright (C) 2021 The Qt Company Ltd.
// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR BSD-3-Clause

import People

BirthdayParty {
    host: Person {
        name: "Bob Jones"
        shoe_size: 12
    }
    guests: [
        Person { name: "Leo Hodges" },
        Person { name: "Jack Smith" },
        Person { name: "Anne Brown" }
    ]
}

People/qmldir

module People
typeinfo coercion.qmltypes
Main 1.0 Main.qml