Add example showing the benefits of using bindable properties

Added two examples for modeling a subscription service: signal/slot
connection-based and bindable property-based. The examples are based
on the example from Fabian's Qt WS talk about the bindable properties.

Pick-to: 6.2
Task-number: QTBUG-97655
Change-Id: I0345913b8b6e5c40b8477e128d36483598bdfcaa
Reviewed-by: Qt CI Bot <qt_ci_bot@qt-project.org>
Reviewed-by: Ivan Solovev <ivan.solovev@qt.io>
Reviewed-by: Fabian Kosmale <fabian.kosmale@qt.io>

1 files changed, 90 insertions, 0 deletions

diff --git a/examples/corelib/bindableproperties/bindablesubscription/bindablesubscription.cpp b/examples/corelib/bindableproperties/bindablesubscription/bindablesubscription.cpp
new file mode 100644
index 0000000000..d962216cd9
--- /dev/null
+++ b/examples/corelib/bindableproperties/bindablesubscription/bindablesubscription.cpp
@@ -0,0 +1,90 @@
+/****************************************************************************
+**
+** Copyright (C) 2021 The Qt Company Ltd.
+** Contact: https://www.qt.io/licensing/
+**
+** This file is part of the examples of the Qt Toolkit.
+**
+** $QT_BEGIN_LICENSE:BSD$
+** Commercial License Usage
+** Licensees holding valid commercial Qt licenses may use this file in
+** accordance with the commercial license agreement provided with the
+** Software or, alternatively, in accordance with the terms contained in
+** a written agreement between you and The Qt Company. For licensing terms
+** and conditions see https://www.qt.io/terms-conditions. For further
+** information use the contact form at https://www.qt.io/contact-us.
+**
+** BSD License Usage
+** Alternatively, you may use this file under the terms of the BSD license
+** as follows:
+**
+** "Redistribution and use in source and binary forms, with or without
+** modification, are permitted provided that the following conditions are
+** met:
+**   * Redistributions of source code must retain the above copyright
+**     notice, this list of conditions and the following disclaimer.
+**   * Redistributions in binary form must reproduce the above copyright
+**     notice, this list of conditions and the following disclaimer in
+**     the documentation and/or other materials provided with the
+**     distribution.
+**   * Neither the name of The Qt Company Ltd nor the names of its
+**     contributors may be used to endorse or promote products derived
+**     from this software without specific prior written permission.
+**
+**
+** THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+** "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+** LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+** A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+** OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+** SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+** LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+** DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+** THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+** (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+** OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE."
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+#include "bindablesubscription.h"
+#include "bindableuser.h"
+
+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::None && m_user->age() > 12;
+    });
+}
+
+void BindableSubscription::setDuration(Duration newDuration)
+{
+    m_duration = newDuration;
+}
+
+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::None)
+        return 0;
+
+    return (m_user->country() == BindableUser::Norway) ? 100 : 80;
+}