qt 6.5.1 original

examples/corelib/bindableproperties/CMakeLists.txt

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+qt_internal_add_example(bindablesubscription)
+qt_internal_add_example(subscription)

examples/corelib/bindableproperties/bindableproperties.pro

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+TEMPLATE = subdirs
+SUBDIRS = \
+    bindablesubscription \
+    subscription

examples/corelib/bindableproperties/bindablesubscription/CMakeLists.txt

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+# Copyright (C) 2022 The Qt Company Ltd.
+# SPDX-License-Identifier: BSD-3-Clause
+
+cmake_minimum_required(VERSION 3.16)
+project(bindablesubscription LANGUAGES CXX)
+
+if(NOT DEFINED INSTALL_EXAMPLESDIR)
+    set(INSTALL_EXAMPLESDIR "examples")
+endif()
+
+set(INSTALL_EXAMPLEDIR "${INSTALL_EXAMPLESDIR}/corelib/bindableproperties/bindablesubscription")
+
+find_package(Qt6 REQUIRED COMPONENTS Core Gui Widgets)
+
+qt_standard_project_setup()
+
+qt_add_executable(bindablesubscription
+    ../shared/subscriptionwindow.cpp ../shared/subscriptionwindow.h ../shared/subscriptionwindow.ui
+    main.cpp
+    bindablesubscription.cpp bindablesubscription.h
+    bindableuser.cpp bindableuser.h
+)
+
+target_link_libraries(bindablesubscription PRIVATE
+    Qt6::Core
+    Qt6::Gui
+    Qt6::Widgets
+)
+
+# Resources:
+set(countries_resource_files
+    "../shared/finland.png"
+    "../shared/germany.png"
+    "../shared/norway.png"
+)
+
+qt_add_resources(bindablesubscription "countries"
+    PREFIX
+        "/"
+    BASE
+        "../shared"
+    FILES
+        ${countries_resource_files}
+)
+
+install(TARGETS bindablesubscription
+    RUNTIME DESTINATION "${INSTALL_EXAMPLEDIR}"
+    BUNDLE DESTINATION "${INSTALL_EXAMPLEDIR}"
+    LIBRARY DESTINATION "${INSTALL_EXAMPLEDIR}"
+)

examples/corelib/bindableproperties/bindablesubscription/bindablesubscription.cpp

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+// Copyright (C) 2021 The Qt Company Ltd.
+// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR BSD-3-Clause
+
+#include "bindablesubscription.h"
+#include "bindableuser.h"
+
+//! [binding-expressions]
+
+BindableSubscription::BindableSubscription(BindableUser *user) : m_user(user)
+{
+    Q_ASSERT(user);
+
+    m_price.setBinding([this] { return qRound(calculateDiscount() * m_duration * basePrice()); });
+
+    m_isValid.setBinding([this] {
+        return m_user->country() != BindableUser::Country::AnyCountry && m_user->age() > 12;
+    });
+}
+
+//! [binding-expressions]
+
+//! [set-duration]
+
+void BindableSubscription::setDuration(Duration newDuration)
+{
+    m_duration = newDuration;
+}
+
+//! [set-duration]
+
+double BindableSubscription::calculateDiscount() const
+{
+    switch (m_duration) {
+    case Monthly:
+        return 1;
+    case Quarterly:
+        return 0.9;
+    case Yearly:
+        return 0.6;
+    }
+    Q_ASSERT(false);
+    return -1;
+}
+
+int BindableSubscription::basePrice() const
+{
+    if (m_user->country() == BindableUser::Country::AnyCountry)
+        return 0;
+
+    return (m_user->country() == BindableUser::Country::Norway) ? 100 : 80;
+}

examples/corelib/bindableproperties/bindablesubscription/bindablesubscription.h

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+// Copyright (C) 2021 The Qt Company Ltd.
+// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR BSD-3-Clause
+
+#ifndef BINDABLESUBSCRIPTION_H
+#define BINDABLESUBSCRIPTION_H
+
+#include <QPointer>
+#include <QProperty>
+
+class BindableUser;
+
+//! [bindable-subscription-class]
+
+class BindableSubscription
+{
+public:
+    enum Duration { Monthly = 1, Quarterly = 3, Yearly = 12 };
+
+    BindableSubscription(BindableUser *user);
+    BindableSubscription(const BindableSubscription &) = delete;
+
+    int price() const { return m_price; }
+    QBindable<int> bindablePrice() { return &m_price; }
+
+    Duration duration() const { return m_duration; }
+    void setDuration(Duration newDuration);
+    QBindable<Duration> bindableDuration() { return &m_duration; }
+
+    bool isValid() const { return m_isValid; }
+    QBindable<bool> bindableIsValid() { return &m_isValid; }
+
+private:
+    double calculateDiscount() const;
+    int basePrice() const;
+
+    BindableUser *m_user;
+    QProperty<Duration> m_duration { Monthly };
+    QProperty<int> m_price { 0 };
+    QProperty<bool> m_isValid { false };
+};
+
+//! [bindable-subscription-class]
+
+#endif // BNDABLESUBSCRIPTION_H

examples/corelib/bindableproperties/bindablesubscription/bindablesubscription.pro

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+QT += widgets
+TARGET = bindablesubscription
+
+SOURCES += main.cpp \
+    bindablesubscription.cpp \
+    bindableuser.cpp \
+    ../shared/subscriptionwindow.cpp
+
+target.path = $$[QT_INSTALL_EXAMPLES]/corelib/bindableproperties/bindablesubscription
+INSTALLS += target
+
+FORMS += \
+    ../shared/subscriptionwindow.ui
+
+HEADERS += \
+    bindablesubscription.h \
+    bindableuser.h \
+    ../shared/subscriptionwindow.h
+
+RESOURCES += \
+    ../shared/countries.qrc
+

examples/corelib/bindableproperties/bindablesubscription/bindableuser.cpp

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+// Copyright (C) 2021 The Qt Company Ltd.
+// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR BSD-3-Clause
+
+#include "bindableuser.h"
+
+//! [bindable-user-setters]
+
+void BindableUser::setCountry(Country country)
+{
+    m_country = country;
+}
+
+void BindableUser::setAge(int age)
+{
+    m_age = age;
+}
+
+//! [bindable-user-setters]

examples/corelib/bindableproperties/bindablesubscription/bindableuser.h

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+// Copyright (C) 2021 The Qt Company Ltd.
+// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR BSD-3-Clause
+
+#ifndef BINDABLEUSER_H
+#define BINDABLEUSER_H
+
+#include <QLocale>
+#include <QProperty>
+
+//! [bindable-user-class]
+
+class BindableUser
+{
+public:
+    using Country = QLocale::Territory;
+
+public:
+    BindableUser() = default;
+    BindableUser(const BindableUser &) = delete;
+
+    Country country() const { return m_country; }
+    void setCountry(Country country);
+    QBindable<Country> bindableCountry() { return &m_country; }
+
+    int age() const { return m_age; }
+    void setAge(int age);
+    QBindable<int> bindableAge() { return &m_age; }
+
+private:
+    QProperty<Country> m_country { QLocale::AnyTerritory };
+    QProperty<int> m_age { 0 };
+};
+
+//! [bindable-user-class]
+
+#endif // BINDABLEUSER_H

examples/corelib/bindableproperties/bindablesubscription/main.cpp

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+// Copyright (C) 2021 The Qt Company Ltd.
+// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR BSD-3-Clause
+
+#include "../shared/subscriptionwindow.h"
+#include "bindablesubscription.h"
+#include "bindableuser.h"
+
+#include <QApplication>
+#include <QButtonGroup>
+#include <QLabel>
+#include <QPushButton>
+#include <QRadioButton>
+#include <QSpinBox>
+
+int main(int argc, char *argv[])
+{
+    QApplication a(argc, argv);
+    BindableUser user;
+    BindableSubscription subscription(&user);
+
+    SubscriptionWindow w;
+
+    // Initialize subscription data
+    QRadioButton *monthly = w.findChild<QRadioButton *>("btnMonthly");
+    QObject::connect(monthly, &QRadioButton::clicked, [&] {
+        subscription.setDuration(BindableSubscription::Monthly);
+    });
+    QRadioButton *quarterly = w.findChild<QRadioButton *>("btnQuarterly");
+    QObject::connect(quarterly, &QRadioButton::clicked, [&] {
+        subscription.setDuration(BindableSubscription::Quarterly);
+    });
+    QRadioButton *yearly = w.findChild<QRadioButton *>("btnYearly");
+    QObject::connect(yearly, &QRadioButton::clicked, [&] {
+        subscription.setDuration(BindableSubscription::Yearly);
+    });
+
+    // Initialize user data
+    QPushButton *germany = w.findChild<QPushButton *>("btnGermany");
+    QObject::connect(germany, &QPushButton::clicked, [&] {
+        user.setCountry(BindableUser::Country::Germany);
+    });
+    QPushButton *finland = w.findChild<QPushButton *>("btnFinland");
+    QObject::connect(finland, &QPushButton::clicked, [&] {
+        user.setCountry(BindableUser::Country::Finland);
+    });
+    QPushButton *norway = w.findChild<QPushButton *>("btnNorway");
+    QObject::connect(norway, &QPushButton::clicked, [&] {
+        user.setCountry(BindableUser::Country::Norway);
+    });
+
+    QSpinBox *ageSpinBox = w.findChild<QSpinBox *>("ageSpinBox");
+    QObject::connect(ageSpinBox, &QSpinBox::valueChanged, [&](int value) {
+        user.setAge(value);
+    });
+
+    QLabel *priceDisplay = w.findChild<QLabel *>("priceDisplay");
+
+    // Track price changes
+//! [update-ui]
+    auto priceChangeHandler = subscription.bindablePrice().subscribe([&] {
+        QLocale lc{QLocale::AnyLanguage, user.country()};
+        priceDisplay->setText(lc.toCurrencyString(subscription.price() / subscription.duration()));
+    });
+
+    auto priceValidHandler = subscription.bindableIsValid().subscribe([&] {
+        priceDisplay->setEnabled(subscription.isValid());
+    });
+//! [update-ui]
+
+    w.show();
+    return a.exec();
+}

examples/corelib/bindableproperties/doc/src/bindableproperties.qdoc

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+// Copyright (C) 2021 The Qt Company Ltd.
+// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR GFDL-1.3-no-invariants-only
+
+/*!
+    \example bindableproperties
+    \title Bindable Properties Example
+    \brief Demonstrates how the usage of bindable properties can simplify
+    your C++ code.
+
+    In this example we will demonstrate two approaches for expressing the
+    relationships between different objects depending on each other:
+    signal/slot connection-based and bindable property-based. For this
+    purpose we will consider a subscription service model to calculate the
+    cost of the subscription.
+
+    \image bindable_properties_example.png
+
+    \section1 Modeling Subscription System with Signal/Slot Approach
+
+    Let's first consider the usual pre-Qt 6 implementation.
+    To model the subscription service the \c Subscription class is used:
+
+    \snippet bindableproperties/subscription/subscription.h subscription-class
+
+    It stores the information about the subscription and provides corresponding
+    getters, setters, and notifier signals for informing the listeners about the
+    subscription information changes. It also keeps a pointer to an instance of
+    the \c User class.
+
+    The price of the subscription is calculated based on the duration of the
+    subscription:
+
+    \snippet bindableproperties/subscription/subscription.cpp calculate-discount
+
+    And user's location:
+
+    \snippet bindableproperties/subscription/subscription.cpp calculate-base-price
+
+    When the price changes, the \c priceChanged() signal is emitted, to notify the
+    listeners about the change:
+
+    \snippet bindableproperties/subscription/subscription.cpp calculate-price
+
+    Similarly, when the duration of the subscription changes, the \c durationChanged()
+    signal is emitted.
+
+    \snippet bindableproperties/subscription/subscription.cpp set-duration
+
+    \note Both methods need to check if the data is actually changed and
+    only then emit the signals. \c setDuration() also needs to recalculate
+    the price when the duration has changed.
+
+    The \c Subscription is not valid unless the user has a valid country and
+    age, so the validity is updated in the following way:
+
+    \snippet bindableproperties/subscription/subscription.cpp update-validity
+
+    The \c User class is simple: it stores country and age of the user and
+    provides the corresponding getters, setters, and notifier signals:
+
+    \snippet bindableproperties/subscription/user.h user-class
+
+    \snippet bindableproperties/subscription/user.cpp user-setters
+
+    In the \c main() function we initialize instances of \c User and
+    \c Subscription:
+
+    \snippet bindableproperties/subscription/main.cpp init
+
+    And do the proper signal-slot connections to update the \c user and
+    \c subscription data when UI elements change. That is straightforward,
+    so we will skip this part.
+
+    Next, we connect to \c Subscription::priceChanged() to update the price
+    in the UI when the price changes.
+
+    \snippet bindableproperties/subscription/main.cpp connect-price-changed
+
+    We also connect to \c Subscription::isValidChanged() to disable the price
+    display if the subscription isn't valid.
+
+    \snippet bindableproperties/subscription/main.cpp connect-validity-changed
+
+    Because the subscription price and validity also depend on the user's
+    country and age, we also need to connect to the \c User::countryChanged()
+    and \c User::ageChanged() signals and update \c subscription accordingly.
+
+    \snippet bindableproperties/subscription/main.cpp connect-user
+
+    This works, but there are some problems:
+
+    \list
+    \li There's a lot of boilerplate code for the signal-slot connections
+    in order to properly track changes to both \c user and \c subscription.
+    If any of the dependencies of the price changes, we need to remember to emit the
+    corresponding notifier signals, recalculate the price, and update it in
+    the UI.
+    \li If more dependencies for price calculation are added in the future, we'll
+    need to add more signal-slot connections and make sure all the dependencies
+    are properly updated whenever any of them changes. The overall complexity
+    will grow, and the code will become harder to maintain.
+    \li The \c Subscription and \c User classes depend on the metaobject system
+    to be able to use the signal/slot mechanism.
+    \endlist
+
+    Can we do better?
+
+    \section1 Modeling Subscription System with Bindbable Properties
+
+    Now let's see how the \l {Qt Bindable Properties} can help to solve the
+    same problem. First, let's have a look at the \c BindableSubscription class,
+    which is similar to the \c Subscription class, but is implemented using
+    bindable properties:
+
+    \snippet bindableproperties/bindablesubscription/bindablesubscription.h bindable-subscription-class
+
+    The first difference we can notice, is that the data fields are now wrapped
+    inside \l QProperty classes, and the notifier signals (and as a consequence the
+    dependency from the metaobject system) are gone, and new methods returning a
+    \l QBindable for each \l QProperty are added instead. The \c calculatePrice()
+    and \c updateValidty() methods are also removed. We'll see below why they aren't
+    needed anymore.
+
+    The \c BindableUser class differs from the \c User class in a similar way:
+
+    \snippet bindableproperties/bindablesubscription/bindableuser.h bindable-user-class
+
+    The second difference is in the implementation of these classes. First of
+    all, the dependencies between \c subscription and \c user are now tracked via
+    binding expressions:
+
+    \snippet bindableproperties/bindablesubscription/bindablesubscription.cpp binding-expressions
+
+    Behind the scenes the bindable properties track the dependency changes and
+    update the property's value whenever a change is detected. So if, for example,
+    user's country or age is changed, subscription's price and validity will be
+    updated automatically.
+
+    Another difference is that the setters are now trivial:
+
+    \snippet bindableproperties/bindablesubscription/bindablesubscription.cpp set-duration
+
+    \snippet bindableproperties/bindablesubscription/bindableuser.cpp bindable-user-setters
+
+    There's no need to check inside the setters if the property's value has
+    actually changed, \l QProperty already does that. The dependent properties
+    will be notified about the change only if the value has actually changed.
+
+    The code for updating the information about the price in the UI is also
+    simplified:
+
+    \snippet bindableproperties/bindablesubscription/main.cpp update-ui
+
+    We subscribe to changes via \c bindablePrice() and \c bindableIsValid()
+    and update the price display accordingly when any of these properties
+    changes the value. The subscriptions will stay alive as long as the
+    corresponding handlers are alive.
+
+    Also note that the copy constructors of both \c BindableSubscription and
+    \c BindableUser are disabled, since it's not defined what should happen
+    with their bindings when copying.
+
+    As you can see, the code became much simpler, and the problems mentioned
+    above are solved:
+
+    \list
+    \li The boilerplate code for the signal-slot connections is removed, the
+    dependencies are now tracked automatically.
+    \li The code is easier to maintain. Adding more dependencies in the future
+    will only require adding the corresponding bindable properties and setting
+    the binding expressions that reflect the relationships between each other.
+    \li The \c Subscription and \c User classes don't depend on the metaobject
+    system anymore. Of course, you can still expose them to the metaobject
+    system and add \l {Q_PROPERTY}s if you need, and have the advantages of
+    bindable properties both in \c C++ and \c QML code. You can use the
+    \l QObjectBindableProperty class for that.
+    \endlist
+*/

examples/corelib/bindableproperties/shared/countries.qrc

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+<RCC>
+    <qresource prefix="/">
+        <file>germany.png</file>
+        <file>norway.png</file>
+        <file>finland.png</file>
+    </qresource>
+</RCC>

examples/corelib/bindableproperties/shared/subscriptionwindow.cpp

@@ -0,0 +1,16 @@
+// Copyright (C) 2021 The Qt Company Ltd.
+// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR BSD-3-Clause
+
+#include "subscriptionwindow.h"
+#include "ui_subscriptionwindow.h"
+
+SubscriptionWindow::SubscriptionWindow(QWidget *parent)
+    : QWidget(parent), ui(new Ui::SubscriptionWindow)
+{
+    ui->setupUi(this);
+}
+
+SubscriptionWindow::~SubscriptionWindow()
+{
+    delete ui;
+}

examples/corelib/bindableproperties/shared/subscriptionwindow.h

@@ -0,0 +1,29 @@
+// Copyright (C) 2021 The Qt Company Ltd.
+// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR BSD-3-Clause
+
+#ifndef SUBSCRIPTIONWINDOW_H
+#define SUBSCRIPTIONWINDOW_H
+
+#include <QWidget>
+
+QT_BEGIN_NAMESPACE
+namespace Ui {
+class SubscriptionWindow;
+}
+QT_END_NAMESPACE
+
+class User;
+
+class SubscriptionWindow : public QWidget
+{
+    Q_OBJECT
+
+public:
+    explicit SubscriptionWindow(QWidget *parent = nullptr);
+    ~SubscriptionWindow();
+
+private:
+    Ui::SubscriptionWindow *ui;
+};
+
+#endif // SUBSCRIPTIONWINDOW_H

examples/corelib/bindableproperties/shared/subscriptionwindow.ui

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+<?xml version="1.0" encoding="UTF-8"?>
+<ui version="4.0">
+ <class>SubscriptionWindow</class>
+ <widget class="QWidget" name="SubscriptionWindow">
+  <property name="geometry">
+   <rect>
+    <x>0</x>
+    <y>0</y>
+    <width>639</width>
+    <height>269</height>
+   </rect>
+  </property>
+  <property name="windowTitle">
+   <string>Subscription</string>
+  </property>
+  <layout class="QHBoxLayout" name="horizontalLayout_5">
+   <item>
+    <layout class="QVBoxLayout" name="verticalLayout">
+     <item>
+      <layout class="QHBoxLayout" name="horizontalLayout_4" stretch="0,0,0,0">
+       <item>
+        <spacer name="horizontalSpacer_3">
+         <property name="orientation">
+          <enum>Qt::Horizontal</enum>
+         </property>
+         <property name="sizeHint" stdset="0">
+          <size>
+           <width>40</width>
+           <height>20</height>
+          </size>
+         </property>
+        </spacer>
+       </item>
+       <item>
+        <widget class="QPushButton" name="btnGermany">
+         <property name="toolTip">
+          <string>Germany</string>
+         </property>
+         <property name="text">
+          <string/>
+         </property>
+         <property name="icon">
+          <iconset>
+           <normaloff>:/germany.png</normaloff>:/germany.png</iconset>
+         </property>
+         <property name="iconSize">
+          <size>
+           <width>32</width>
+           <height>32</height>
+          </size>
+         </property>
+        </widget>
+       </item>
+       <item>
+        <widget class="QPushButton" name="btnNorway">
+         <property name="toolTip">
+          <string>Norway</string>
+         </property>
+         <property name="text">
+          <string/>
+         </property>
+         <property name="icon">
+          <iconset>
+           <normaloff>:/norway.png</normaloff>:/norway.png</iconset>
+         </property>
+         <property name="iconSize">
+          <size>
+           <width>32</width>
+           <height>32</height>
+          </size>
+         </property>
+        </widget>
+       </item>
+       <item>
+        <widget class="QPushButton" name="btnFinland">
+         <property name="toolTip">
+          <string>Finland</string>
+         </property>
+         <property name="text">
+          <string/>
+         </property>
+         <property name="icon">
+          <iconset>
+           <normaloff>:/finland.png</normaloff>:/finland.png</iconset>
+         </property>
+         <property name="iconSize">
+          <size>
+           <width>32</width>
+           <height>32</height>
+          </size>
+         </property>
+        </widget>
+       </item>
+      </layout>
+     </item>
+     <item>
+      <layout class="QHBoxLayout" name="horizontalLayout">
+       <item>
+        <widget class="QLabel" name="ageLabel">
+         <property name="font">
+          <font>
+           <pointsize>14</pointsize>
+           <weight>75</weight>
+           <bold>true</bold>
+          </font>
+         </property>
+         <property name="text">
+          <string>Age</string>
+         </property>
+         <property name="margin">
+          <number>3</number>
+         </property>
+        </widget>
+       </item>
+       <item>
+        <widget class="QSpinBox" name="ageSpinBox">
+         <property name="sizePolicy">
+          <sizepolicy hsizetype="Minimum" vsizetype="Fixed">
+           <horstretch>0</horstretch>
+           <verstretch>0</verstretch>
+          </sizepolicy>
+         </property>
+         <property name="minimumSize">
+          <size>
+           <width>80</width>
+           <height>0</height>
+          </size>
+         </property>
+         <property name="value">
+          <number>0</number>
+         </property>
+        </widget>
+       </item>
+       <item>
+        <spacer name="horizontalSpacer">
+         <property name="orientation">
+          <enum>Qt::Horizontal</enum>
+         </property>
+         <property name="sizeHint" stdset="0">
+          <size>
+           <width>40</width>
+           <height>20</height>
+          </size>
+         </property>
+        </spacer>
+       </item>
+      </layout>
+     </item>
+     <item>
+      <spacer name="verticalSpacer">
+       <property name="orientation">
+        <enum>Qt::Vertical</enum>
+       </property>
+       <property name="sizeHint" stdset="0">
+        <size>
+         <width>20</width>
+         <height>40</height>
+        </size>
+       </property>
+      </spacer>
+     </item>
+     <item>
+      <layout class="QHBoxLayout" name="horizontalLayout_2">
+       <item>
+        <widget class="QLabel" name="intervalLabel">
+         <property name="font">
+          <font>
+           <pointsize>14</pointsize>
+           <weight>75</weight>
+           <bold>true</bold>
+          </font>
+         </property>
+         <property name="text">
+          <string>Interval</string>
+         </property>
+         <property name="margin">
+          <number>3</number>
+         </property>
+        </widget>
+       </item>
+       <item>
+        <widget class="QRadioButton" name="btnMonthly">
+         <property name="text">
+          <string>Monthly</string>
+         </property>
+         <property name="checked">
+          <bool>true</bool>
+         </property>
+        </widget>
+       </item>
+       <item>
+        <widget class="QRadioButton" name="btnQuarterly">
+         <property name="text">
+          <string>Quarterly</string>
+         </property>
+        </widget>
+       </item>
+       <item>
+        <widget class="QRadioButton" name="btnYearly">
+         <property name="text">
+          <string>Yearly</string>
+         </property>
+        </widget>
+       </item>
+      </layout>
+     </item>
+     <item>
+      <spacer name="verticalSpacer_2">
+       <property name="orientation">
+        <enum>Qt::Vertical</enum>
+       </property>
+       <property name="sizeHint" stdset="0">
+        <size>
+         <width>20</width>
+         <height>40</height>
+        </size>
+       </property>
+      </spacer>
+     </item>
+     <item>
+      <layout class="QHBoxLayout" name="horizontalLayout_3">
+       <item>
+        <widget class="QLabel" name="priceLabel">
+         <property name="font">
+          <font>
+           <pointsize>14</pointsize>
+           <weight>75</weight>
+           <bold>true</bold>
+          </font>
+         </property>
+         <property name="text">
+          <string>Price/month</string>
+         </property>
+         <property name="margin">
+          <number>3</number>
+         </property>
+        </widget>
+       </item>
+       <item>
+        <widget class="QLabel" name="priceDisplay">
+         <property name="text">
+          <string>0.0</string>
+         </property>
+        </widget>
+       </item>
+       <item>
+        <spacer name="horizontalSpacer_2">
+         <property name="orientation">
+          <enum>Qt::Horizontal</enum>
+         </property>
+         <property name="sizeHint" stdset="0">
+          <size>
+           <width>40</width>
+           <height>20</height>
+          </size>
+         </property>
+        </spacer>
+       </item>
+      </layout>
+     </item>
+     <item>
+      <spacer name="verticalSpacer_3">
+       <property name="orientation">
+        <enum>Qt::Vertical</enum>
+       </property>
+       <property name="sizeHint" stdset="0">
+        <size>
+         <width>20</width>
+         <height>40</height>
+        </size>
+       </property>
+      </spacer>
+     </item>
+    </layout>
+   </item>
+  </layout>
+ </widget>
+ <resources/>
+ <connections/>
+</ui>

examples/corelib/bindableproperties/subscription/CMakeLists.txt

@@ -0,0 +1,50 @@
+# Copyright (C) 2022 The Qt Company Ltd.
+# SPDX-License-Identifier: BSD-3-Clause
+
+cmake_minimum_required(VERSION 3.16)
+project(subscription LANGUAGES CXX)
+
+if(NOT DEFINED INSTALL_EXAMPLESDIR)
+    set(INSTALL_EXAMPLESDIR "examples")
+endif()
+
+set(INSTALL_EXAMPLEDIR "${INSTALL_EXAMPLESDIR}/corelib/bindableproperties/subscription")
+
+find_package(Qt6 REQUIRED COMPONENTS Core Gui Widgets)
+
+qt_standard_project_setup()
+
+qt_add_executable(subscription
+    ../shared/subscriptionwindow.cpp ../shared/subscriptionwindow.h ../shared/subscriptionwindow.ui
+    main.cpp
+    subscription.cpp subscription.h
+    user.cpp user.h
+)
+
+target_link_libraries(subscription PRIVATE
+    Qt6::Core
+    Qt6::Gui
+    Qt6::Widgets
+)
+
+# Resources:
+set(countries_resource_files
+    "../shared/finland.png"
+    "../shared/germany.png"
+    "../shared/norway.png"
+)
+
+qt_add_resources(subscription "countries"
+    PREFIX
+        "/"
+    BASE
+        "../shared"
+    FILES
+        ${countries_resource_files}
+)
+
+install(TARGETS subscription
+    RUNTIME DESTINATION "${INSTALL_EXAMPLEDIR}"
+    BUNDLE DESTINATION "${INSTALL_EXAMPLEDIR}"
+    LIBRARY DESTINATION "${INSTALL_EXAMPLEDIR}"
+)

examples/corelib/bindableproperties/subscription/main.cpp

@@ -0,0 +1,92 @@
+// Copyright (C) 2021 The Qt Company Ltd.
+// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR BSD-3-Clause
+
+#include "../shared/subscriptionwindow.h"
+#include "subscription.h"
+#include "user.h"
+
+#include <QApplication>
+#include <QButtonGroup>
+#include <QLabel>
+#include <QPushButton>
+#include <QRadioButton>
+#include <QSpinBox>
+
+int main(int argc, char *argv[])
+{
+    QApplication a(argc, argv);
+
+//! [init]
+    User user;
+    Subscription subscription(&user);
+//! [init]
+
+    SubscriptionWindow w;
+
+    // Initialize subscription data
+    QRadioButton *monthly = w.findChild<QRadioButton *>("btnMonthly");
+    QObject::connect(monthly, &QRadioButton::clicked, &subscription, [&] {
+        subscription.setDuration(Subscription::Monthly);
+    });
+    QRadioButton *quarterly = w.findChild<QRadioButton *>("btnQuarterly");
+    QObject::connect(quarterly, &QRadioButton::clicked, &subscription, [&] {
+        subscription.setDuration(Subscription::Quarterly);
+    });
+    QRadioButton *yearly = w.findChild<QRadioButton *>("btnYearly");
+    QObject::connect(yearly, &QRadioButton::clicked, &subscription, [&] {
+        subscription.setDuration(Subscription::Yearly);
+    });
+
+    // Initialize user data
+    QPushButton *germany = w.findChild<QPushButton *>("btnGermany");
+    QObject::connect(germany, &QPushButton::clicked, &user, [&] {
+        user.setCountry(User::Country::Germany);
+    });
+    QPushButton *finland = w.findChild<QPushButton *>("btnFinland");
+    QObject::connect(finland, &QPushButton::clicked, &user, [&] {
+        user.setCountry(User::Country::Finland);
+    });
+    QPushButton *norway = w.findChild<QPushButton *>("btnNorway");
+    QObject::connect(norway, &QPushButton::clicked, &user, [&] {
+        user.setCountry(User::Country::Norway);
+    });
+
+    QSpinBox *ageSpinBox = w.findChild<QSpinBox *>("ageSpinBox");
+    QObject::connect(ageSpinBox, &QSpinBox::valueChanged, &user, [&](int value) {
+        user.setAge(value);
+    });
+
+    // Initialize price data
+    QLabel *priceDisplay = w.findChild<QLabel *>("priceDisplay");
+    priceDisplay->setText(QString::number(subscription.price()));
+    priceDisplay->setEnabled(subscription.isValid());
+
+    // Track the price changes
+
+//! [connect-price-changed]
+    QObject::connect(&subscription, &Subscription::priceChanged, [&] {
+        QLocale lc{QLocale::AnyLanguage, user.country()};
+        priceDisplay->setText(lc.toCurrencyString(subscription.price() / subscription.duration()));
+    });
+//! [connect-price-changed]
+
+//! [connect-validity-changed]
+    QObject::connect(&subscription, &Subscription::isValidChanged, [&] {
+        priceDisplay->setEnabled(subscription.isValid());
+    });
+//! [connect-validity-changed]
+
+//! [connect-user]
+    QObject::connect(&user, &User::countryChanged, [&] {
+        subscription.calculatePrice();
+        subscription.updateValidity();
+    });
+
+    QObject::connect(&user, &User::ageChanged, [&] {
+        subscription.updateValidity();
+    });
+//! [connect-user]
+
+    w.show();
+    return a.exec();
+}

examples/corelib/bindableproperties/subscription/subscription.cpp

@@ -0,0 +1,79 @@
+// Copyright (C) 2021 The Qt Company Ltd.
+// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR BSD-3-Clause
+
+#include "subscription.h"
+#include "user.h"
+
+Subscription::Subscription(User *user) : m_user(user)
+{
+    Q_ASSERT(user);
+}
+
+//! [calculate-price]
+
+void Subscription::calculatePrice()
+{
+    const auto oldPrice = m_price;
+
+    m_price = qRound(calculateDiscount() * m_duration * basePrice());
+    if (m_price != oldPrice)
+        emit priceChanged();
+}
+
+//! [calculate-price]
+
+//! [set-duration]
+
+void Subscription::setDuration(Duration newDuration)
+{
+    if (newDuration != m_duration) {
+        m_duration = newDuration;
+        calculatePrice();
+        emit durationChanged();
+    }
+}
+
+//! [set-duration]
+
+//! [calculate-discount]
+
+double Subscription::calculateDiscount() const
+{
+    switch (m_duration) {
+    case Monthly:
+        return 1;
+    case Quarterly:
+        return 0.9;
+    case Yearly:
+        return 0.6;
+    }
+    Q_ASSERT(false);
+    return -1;
+}
+
+//! [calculate-discount]
+
+//! [calculate-base-price]
+
+int Subscription::basePrice() const
+{
+    if (m_user->country() == User::Country::AnyTerritory)
+        return 0;
+
+    return (m_user->country() == User::Country::Norway) ? 100 : 80;
+}
+
+//! [calculate-base-price]
+
+//! [update-validity]
+
+void Subscription::updateValidity()
+{
+    bool isValid = m_isValid;
+    m_isValid = m_user->country() != User::Country::AnyTerritory && m_user->age() > 12;
+
+    if (m_isValid != isValid)
+        emit isValidChanged();
+}
+
+//! [update-validity]

examples/corelib/bindableproperties/subscription/subscription.h

@@ -0,0 +1,48 @@
+// Copyright (C) 2021 The Qt Company Ltd.
+// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR BSD-3-Clause
+
+#ifndef SUBSCRIPTION_H
+#define SUBSCRIPTION_H
+
+#include <QObject>
+#include <QPointer>
+
+class User;
+
+//! [subscription-class]
+
+class Subscription : public QObject
+{
+    Q_OBJECT
+public:
+    enum Duration { Monthly = 1, Quarterly = 3, Yearly = 12 };
+
+    Subscription(User *user);
+
+    void calculatePrice();
+    int price() const { return m_price; }
+
+    Duration duration() const { return m_duration; }
+    void setDuration(Duration newDuration);
+
+    bool isValid() const { return m_isValid; }
+    void updateValidity();
+
+signals:
+    void priceChanged();
+    void durationChanged();
+    void isValidChanged();
+
+private:
+    double calculateDiscount() const;
+    int basePrice() const;
+
+    QPointer<User> m_user;
+    Duration m_duration = Monthly;
+    int m_price = 0;
+    bool m_isValid = false;
+};
+
+//! [subscription-class]
+
+#endif // SUBSCRIPTION_H

examples/corelib/bindableproperties/subscription/subscription.pro

@@ -0,0 +1,22 @@
+QT += widgets
+TARGET = subscription
+
+SOURCES += main.cpp \
+    subscription.cpp \
+    user.cpp \
+    ../shared/subscriptionwindow.cpp
+
+target.path = $$[QT_INSTALL_EXAMPLES]/corelib/bindableproperties/subscription
+INSTALLS += target
+
+FORMS += \
+    ../shared/subscriptionwindow.ui
+
+HEADERS += \
+    subscription.h \
+    user.h \
+    ../shared/subscriptionwindow.h
+
+RESOURCES += \
+    ../shared/countries.qrc
+

examples/corelib/bindableproperties/subscription/user.cpp

@@ -0,0 +1,24 @@
+// Copyright (C) 2021 The Qt Company Ltd.
+// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR BSD-3-Clause
+
+#include "user.h"
+
+//! [user-setters]
+
+void User::setCountry(Country country)
+{
+    if (m_country != country) {
+        m_country = country;
+        emit countryChanged();
+    }
+}
+
+void User::setAge(int age)
+{
+    if (m_age != age) {
+        m_age = age;
+        emit ageChanged();
+    }
+}
+
+//! [user-setters]

examples/corelib/bindableproperties/subscription/user.h

@@ -0,0 +1,36 @@
+// Copyright (C) 2021 The Qt Company Ltd.
+// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR BSD-3-Clause
+
+#ifndef USER_H
+#define USER_H
+
+#include <QLocale>
+#include <QObject>
+
+//! [user-class]
+
+class User : public QObject
+{
+    Q_OBJECT
+
+public:
+    using Country = QLocale::Territory;
+
+public:
+    Country country() const { return m_country; }
+    void setCountry(Country country);
+
+    int age() const { return m_age; }
+    void setAge(int age);
+
+signals:
+    void countryChanged();
+    void ageChanged();
+
+private:
+    Country m_country { QLocale::AnyTerritory };
+    int m_age { 0 };
+};
+
+//! [user-class]
+#endif // USER_H