Polish the QML reference examples

- Use member initialization, which allows for using
  constructors from the base classes
- Use qsizetype for indexes
- Use qInfo() instead of qWarning() for printing
- Add spaces/fix formatting

Change-Id: Iebce1b810ce00f29395207d93303363b3b71e52e
Reviewed-by: Cristian Maureira-Fredes <cristian.maureira-fredes@qt.io>
Reviewed-by: Ulf Hermann <ulf.hermann@qt.io>
(cherry picked from commit c442ed4d65b0319e4abd7a931cfb2f1f72842b84)
Reviewed-by: Fabian Kosmale <fabian.kosmale@qt.io>

52 files changed, 279 insertions, 461 deletions

diff --git a/examples/qml/referenceexamples/adding/main.cpp b/examples/qml/referenceexamples/adding/main.cpp
index 6c3920f04b..fbf3e71af7 100644
--- a/examples/qml/referenceexamples/adding/main.cpp
+++ b/examples/qml/referenceexamples/adding/main.cpp
@@ -1,6 +1,6 @@
 /****************************************************************************
 **
-** Copyright (C) 2017 The Qt Company Ltd.
+** Copyright (C) 2021 The Qt Company Ltd.
 ** Contact: https://www.qt.io/licensing/
 **
 ** This file is part of the examples of the Qt Toolkit.
@@ -47,6 +47,7 @@
 ** $QT_END_LICENSE$
 **
 ****************************************************************************/
+
 #include <QCoreApplication>
 #include <QQmlEngine>
 #include <QQmlComponent>
@@ -60,12 +61,13 @@ int main(int argc, char ** argv)
     QQmlEngine engine;
     QQmlComponent component(&engine, QUrl("qrc:example.qml"));
     auto *person = qobject_cast<Person *>(component.create());
-    if (person) {
-        qWarning() << "The person's name is" << person->name();
-        qWarning() << "They wear a" << person->shoeSize() << "sized shoe";
-    } else {
+    if (!person) {
         qWarning() << component.errors();
+        return EXIT_FAILURE;
     }
 
+     qInfo() << "The person's name is" << person->name()
+         << "\nThey wear a" << person->shoeSize() << "sized shoe";
+
     return EXIT_SUCCESS;
 }
diff --git a/examples/qml/referenceexamples/adding/person.cpp b/examples/qml/referenceexamples/adding/person.cpp
index de4a33dd00..4741442cf0 100644
--- a/examples/qml/referenceexamples/adding/person.cpp
+++ b/examples/qml/referenceexamples/adding/person.cpp
@@ -1,6 +1,6 @@
 /****************************************************************************
 **
-** Copyright (C) 2017 The Qt Company Ltd.
+** Copyright (C) 2021 The Qt Company Ltd.
 ** Contact: https://www.qt.io/licensing/
 **
 ** This file is part of the examples of the Qt Toolkit.
@@ -47,14 +47,10 @@
 ** $QT_END_LICENSE$
 **
 ****************************************************************************/
+
 #include "person.h"
 
 // ![0]
-Person::Person(QObject *parent)
-: QObject(parent), m_shoeSize(0)
-{
-}
-
 QString Person::name() const
 {
     return m_name;
diff --git a/examples/qml/referenceexamples/adding/person.h b/examples/qml/referenceexamples/adding/person.h
index 530c335dee..03a72d184f 100644
--- a/examples/qml/referenceexamples/adding/person.h
+++ b/examples/qml/referenceexamples/adding/person.h
@@ -1,6 +1,6 @@
 /****************************************************************************
 **
-** Copyright (C) 2017 The Qt Company Ltd.
+** Copyright (C) 2021 The Qt Company Ltd.
 ** Contact: https://www.qt.io/licensing/
 **
 ** This file is part of the examples of the Qt Toolkit.
@@ -47,6 +47,7 @@
 ** $QT_END_LICENSE$
 **
 ****************************************************************************/
+
 #ifndef PERSON_H
 #define PERSON_H
 
@@ -61,7 +62,7 @@ class Person : public QObject
     Q_PROPERTY(int shoeSize READ shoeSize WRITE setShoeSize)
     QML_ELEMENT
 public:
-    Person(QObject *parent = nullptr);
+    using QObject::QObject;
 
     QString name() const;
     void setName(const QString &);
@@ -71,7 +72,7 @@ public:
 
 private:
     QString m_name;
-    int m_shoeSize;
+    int m_shoeSize = 0;
 };
 //![0]
 
diff --git a/examples/qml/referenceexamples/attached/birthdayparty.cpp b/examples/qml/referenceexamples/attached/birthdayparty.cpp
index 9aed5df621..fc27a22631 100644
--- a/examples/qml/referenceexamples/attached/birthdayparty.cpp
+++ b/examples/qml/referenceexamples/attached/birthdayparty.cpp
@@ -1,6 +1,6 @@
 /****************************************************************************
 **
-** Copyright (C) 2017 The Qt Company Ltd.
+** Copyright (C) 2021 The Qt Company Ltd.
 ** Contact: https://www.qt.io/licensing/
 **
 ** This file is part of the examples of the Qt Toolkit.
@@ -47,12 +47,8 @@
 ** $QT_END_LICENSE$
 **
 ****************************************************************************/
-#include "birthdayparty.h"
 
-BirthdayPartyAttached::BirthdayPartyAttached(QObject *object)
-: QObject(object)
-{
-}
+#include "birthdayparty.h"
 
 QDate BirthdayPartyAttached::rsvp() const
 {
@@ -64,11 +60,6 @@ void BirthdayPartyAttached::setRsvp(QDate d)
     m_rsvp = d;
 }
 
-BirthdayParty::BirthdayParty(QObject *parent)
-: QObject(parent), m_host(nullptr)
-{
-}
-
 Person *BirthdayParty::host() const
 {
     return m_host;
@@ -84,12 +75,12 @@ QQmlListProperty<Person> BirthdayParty::guests()
     return {this, &m_guests};
 }
 
-int BirthdayParty::guestCount() const
+qsizetype BirthdayParty::guestCount() const
 {
     return m_guests.count();
 }
 
-Person *BirthdayParty::guest(int index) const
+Person *BirthdayParty::guest(qsizetype index) const
 {
     return m_guests.at(index);
 }
diff --git a/examples/qml/referenceexamples/attached/birthdayparty.h b/examples/qml/referenceexamples/attached/birthdayparty.h
index 4f2ed1702a..30f5cbbb64 100644
--- a/examples/qml/referenceexamples/attached/birthdayparty.h
+++ b/examples/qml/referenceexamples/attached/birthdayparty.h
@@ -1,6 +1,6 @@
 /****************************************************************************
 **
-** Copyright (C) 2017 The Qt Company Ltd.
+** Copyright (C) 2021 The Qt Company Ltd.
 ** Contact: https://www.qt.io/licensing/
 **
 ** This file is part of the examples of the Qt Toolkit.
@@ -47,6 +47,7 @@
 ** $QT_END_LICENSE$
 **
 ****************************************************************************/
+
 #ifndef BIRTHDAYPARTY_H
 #define BIRTHDAYPARTY_H
 
@@ -61,7 +62,7 @@ class BirthdayPartyAttached : public QObject
     Q_PROPERTY(QDate rsvp READ rsvp WRITE setRsvp)
     QML_ANONYMOUS
 public:
-    BirthdayPartyAttached(QObject *object);
+    using QObject::QObject;
 
     QDate rsvp() const;
     void setRsvp(QDate);
@@ -83,20 +84,20 @@ class BirthdayParty : public QObject
 //! [declare attached]
 
 public:
-    BirthdayParty(QObject *parent = nullptr);
+    using QObject::QObject;
 
     Person *host() const;
     void setHost(Person *);
 
     QQmlListProperty<Person> guests();
-    int guestCount() const;
-    Person *guest(int) const;
+    qsizetype guestCount() const;
+    Person *guest(qsizetype) const;
 
     //! [static attached]
     static BirthdayPartyAttached *qmlAttachedProperties(QObject *);
     //! [static attached]
 private:
-    Person *m_host;
+    Person *m_host = nullptr;
     QList<Person *> m_guests;
 };
 
diff --git a/examples/qml/referenceexamples/attached/main.cpp b/examples/qml/referenceexamples/attached/main.cpp
index 2fceb98ac9..5f8497bed3 100644
--- a/examples/qml/referenceexamples/attached/main.cpp
+++ b/examples/qml/referenceexamples/attached/main.cpp
@@ -1,6 +1,6 @@
 /****************************************************************************
 **
-** Copyright (C) 2017 The Qt Company Ltd.
+** Copyright (C) 2021 The Qt Company Ltd.
 ** Contact: https://www.qt.io/licensing/
 **
 ** This file is part of the examples of the Qt Toolkit.
@@ -47,6 +47,7 @@
 ** $QT_END_LICENSE$
 **
 ****************************************************************************/
+
 #include <QCoreApplication>
 #include <QQmlEngine>
 #include <QQmlComponent>
@@ -63,14 +64,14 @@ int main(int argc, char ** argv)
     auto *party = qobject_cast<BirthdayParty *>(component.create());
 
     if (party && party->host()) {
-        qWarning() << party->host()->name() << "is having a birthday!";
+        qInfo() << party->host()->name() << "is having a birthday!";
 
         if (qobject_cast<Boy *>(party->host()))
-            qWarning() << "He is inviting:";
+            qInfo() << "He is inviting:";
         else
-            qWarning() << "She is inviting:";
+            qInfo() << "She is inviting:";
 
-        for (int ii = 0; ii < party->guestCount(); ++ii) {
+        for (qsizetype ii = 0; ii < party->guestCount(); ++ii) {
             Person *guest = party->guest(ii);
 
             //! [query rsvp]
@@ -81,9 +82,9 @@ int main(int argc, char ** argv)
                 rsvpDate = attached->property("rsvp").toDate();
             //! [query rsvp]
             if (rsvpDate.isNull())
-                qWarning() << "   " << guest->name() << "RSVP date: Hasn't RSVP'd";
+                qInfo() << "   " << guest->name() << "RSVP date: Hasn't RSVP'd";
             else
-                qWarning() << "   " << guest->name() << "RSVP date:" << qPrintable(rsvpDate.toString());
+                qInfo() << "   " << guest->name() << "RSVP date:" << rsvpDate.toString();
         }
 
         return EXIT_SUCCESS;
diff --git a/examples/qml/referenceexamples/attached/person.cpp b/examples/qml/referenceexamples/attached/person.cpp
index 0603644108..4e52da76c8 100644
--- a/examples/qml/referenceexamples/attached/person.cpp
+++ b/examples/qml/referenceexamples/attached/person.cpp
@@ -1,6 +1,6 @@
 /****************************************************************************
 **
-** Copyright (C) 2017 The Qt Company Ltd.
+** Copyright (C) 2021 The Qt Company Ltd.
 ** Contact: https://www.qt.io/licensing/
 **
 ** This file is part of the examples of the Qt Toolkit.
@@ -47,12 +47,8 @@
 ** $QT_END_LICENSE$
 **
 ****************************************************************************/
-#include "person.h"
 
-ShoeDescription::ShoeDescription(QObject *parent)
-: QObject(parent), m_size(0), m_price(0)
-{
-}
+#include "person.h"
 
 int ShoeDescription::size() const
 {
@@ -94,11 +90,6 @@ void ShoeDescription::setPrice(qreal p)
     m_price = p;
 }
 
-Person::Person(QObject *parent)
-: QObject(parent)
-{
-}
-
 QString Person::name() const
 {
     return m_name;
@@ -113,16 +104,3 @@ ShoeDescription *Person::shoe()
 {
     return &m_shoe;
 }
-
-
-Boy::Boy(QObject * parent)
-: Person(parent)
-{
-}
-
-
-Girl::Girl(QObject * parent)
-: Person(parent)
-{
-}
-
diff --git a/examples/qml/referenceexamples/attached/person.h b/examples/qml/referenceexamples/attached/person.h
index 239f4405c0..ddd3baa5f2 100644
--- a/examples/qml/referenceexamples/attached/person.h
+++ b/examples/qml/referenceexamples/attached/person.h
@@ -1,6 +1,6 @@
 /****************************************************************************
 **
-** Copyright (C) 2017 The Qt Company Ltd.
+** Copyright (C) 2021 The Qt Company Ltd.
 ** Contact: https://www.qt.io/licensing/
 **
 ** This file is part of the examples of the Qt Toolkit.
@@ -47,6 +47,7 @@
 ** $QT_END_LICENSE$
 **
 ****************************************************************************/
+
 #ifndef PERSON_H
 #define PERSON_H
 
@@ -63,7 +64,7 @@ class ShoeDescription : public QObject
     Q_PROPERTY(qreal price READ price WRITE setPrice)
     QML_ANONYMOUS
 public:
-    ShoeDescription(QObject *parent = 0);
+    using QObject::QObject;
 
     int size() const;
     void setSize(int);
@@ -76,11 +77,12 @@ public:
 
     qreal price() const;
     void setPrice(qreal);
+
 private:
-    int m_size;
+    int m_size = 0;
     QColor m_color;
     QString m_brand;
-    qreal m_price;
+    qreal m_price = 0;
 };
 
 class Person : public QObject
@@ -90,7 +92,7 @@ class Person : public QObject
     Q_PROPERTY(ShoeDescription *shoe READ shoe)
     QML_ANONYMOUS
 public:
-    Person(QObject *parent = nullptr);
+    using QObject::QObject;
 
     QString name() const;
     void setName(const QString &);
@@ -106,7 +108,7 @@ class Boy : public Person
     Q_OBJECT
     QML_ELEMENT
 public:
-    Boy(QObject * parent = nullptr);
+    using Person::Person;
 };
 
 class Girl : public Person
@@ -114,7 +116,7 @@ class Girl : public Person
     Q_OBJECT
     QML_ELEMENT
 public:
-    Girl(QObject * parent = nullptr);
+    using Person::Person;
 };
 
 #endif // PERSON_H
diff --git a/examples/qml/referenceexamples/binding/birthdayparty.cpp b/examples/qml/referenceexamples/binding/birthdayparty.cpp
index 02a1adbb35..ce86c7faa4 100644
--- a/examples/qml/referenceexamples/binding/birthdayparty.cpp
+++ b/examples/qml/referenceexamples/binding/birthdayparty.cpp
@@ -1,6 +1,6 @@
 /****************************************************************************
 **
-** Copyright (C) 2017 The Qt Company Ltd.
+** Copyright (C) 2021 The Qt Company Ltd.
 ** Contact: https://www.qt.io/licensing/
 **
 ** This file is part of the examples of the Qt Toolkit.
@@ -47,12 +47,8 @@
 ** $QT_END_LICENSE$
 **
 ****************************************************************************/
-#include "birthdayparty.h"
 
-BirthdayPartyAttached::BirthdayPartyAttached(QObject *object)
-: QObject(object)
-{
-}
+#include "birthdayparty.h"
 
 QDate BirthdayPartyAttached::rsvp() const
 {
@@ -67,12 +63,6 @@ void BirthdayPartyAttached::setRsvp(QDate d)
     }
 }
 
-
-BirthdayParty::BirthdayParty(QObject *parent)
-: QObject(parent), m_host(nullptr)
-{
-}
-
 Person *BirthdayParty::host() const
 {
     return m_host;
@@ -90,12 +80,12 @@ QQmlListProperty<Person> BirthdayParty::guests()
     return QQmlListProperty<Person>(this, &m_guests);
 }
 
-int BirthdayParty::guestCount() const
+qsizetype BirthdayParty::guestCount() const
 {
     return m_guests.count();
 }
 
-Person *BirthdayParty::guest(int index) const
+Person *BirthdayParty::guest(qsizetype index) const
 {
     return m_guests.at(index);
 }
@@ -113,7 +103,7 @@ QString BirthdayParty::announcement() const
 
 void BirthdayParty::setAnnouncement(const QString &speak)
 {
-    qWarning() << qPrintable(speak);
+    qWarning().noquote() << speak;
 }
 
 BirthdayPartyAttached *BirthdayParty::qmlAttachedProperties(QObject *object)
diff --git a/examples/qml/referenceexamples/binding/birthdayparty.h b/examples/qml/referenceexamples/binding/birthdayparty.h
index 846a016cfc..2881dfead2 100644
--- a/examples/qml/referenceexamples/binding/birthdayparty.h
+++ b/examples/qml/referenceexamples/binding/birthdayparty.h
@@ -1,6 +1,6 @@
 /****************************************************************************
 **
-** Copyright (C) 2017 The Qt Company Ltd.
+** Copyright (C) 2021 The Qt Company Ltd.
 ** Contact: https://www.qt.io/licensing/
 **
 ** This file is part of the examples of the Qt Toolkit.
@@ -47,6 +47,7 @@
 ** $QT_END_LICENSE$
 **
 ****************************************************************************/
+
 #ifndef BIRTHDAYPARTY_H
 #define BIRTHDAYPARTY_H
 
@@ -62,7 +63,7 @@ class BirthdayPartyAttached : public QObject
     Q_PROPERTY(QDate rsvp READ rsvp WRITE setRsvp NOTIFY rsvpChanged)
     QML_ANONYMOUS
 public:
-    BirthdayPartyAttached(QObject *object);
+    using QObject::QObject;
 
     QDate rsvp() const;
     void setRsvp(QDate);
@@ -86,14 +87,14 @@ class BirthdayParty : public QObject
     QML_ELEMENT
     QML_ATTACHED(BirthdayPartyAttached)
 public:
-    BirthdayParty(QObject *parent = nullptr);
+    using QObject::QObject;
 
     Person *host() const;
     void setHost(Person *);
 
     QQmlListProperty<Person> guests();
-    int guestCount() const;
-    Person *guest(int) const;
+    qsizetype guestCount() const;
+    Person *guest(qsizetype) const;
 
     QString announcement() const;
     void setAnnouncement(const QString &);
@@ -106,7 +107,7 @@ signals:
     void hostChanged();
 
 private:
-    Person *m_host;
+    Person *m_host = nullptr;
     QList<Person *> m_guests;
 };
 
diff --git a/examples/qml/referenceexamples/binding/happybirthdaysong.cpp b/examples/qml/referenceexamples/binding/happybirthdaysong.cpp
index 5f8e6d696e..2722b65e06 100644
--- a/examples/qml/referenceexamples/binding/happybirthdaysong.cpp
+++ b/examples/qml/referenceexamples/binding/happybirthdaysong.cpp
@@ -50,10 +50,9 @@
 #include "happybirthdaysong.h"
 #include <QTimer>
 
-HappyBirthdaySong::HappyBirthdaySong(QObject *parent)
-: QObject(parent), m_line(-1)
+HappyBirthdaySong::HappyBirthdaySong(QObject *parent) :
+    QObject(parent)
 {
-    setName(QString());
     auto *timer = new QTimer(this);
     QObject::connect(timer, &QTimer::timeout, this, &HappyBirthdaySong::advance);
     timer->start(1000);
diff --git a/examples/qml/referenceexamples/binding/happybirthdaysong.h b/examples/qml/referenceexamples/binding/happybirthdaysong.h
index c84e9d9e5e..078bdac72b 100644
--- a/examples/qml/referenceexamples/binding/happybirthdaysong.h
+++ b/examples/qml/referenceexamples/binding/happybirthdaysong.h
@@ -64,7 +64,7 @@ class HappyBirthdaySong : public QObject, public QQmlPropertyValueSource
     Q_INTERFACES(QQmlPropertyValueSource)
     QML_ELEMENT
 public:
-    HappyBirthdaySong(QObject *parent = nullptr);
+    explicit HappyBirthdaySong(QObject *parent = nullptr);
 
     void setTarget(const QQmlProperty &) override;
 
@@ -77,7 +77,7 @@ private slots:
 signals:
     void nameChanged();
 private:
-    int m_line;
+    qsizetype m_line = -1;
     QStringList m_lyrics;
     QQmlProperty m_target;
     QString m_name;
diff --git a/examples/qml/referenceexamples/binding/main.cpp b/examples/qml/referenceexamples/binding/main.cpp
index 2e9995fcd8..a100497659 100644
--- a/examples/qml/referenceexamples/binding/main.cpp
+++ b/examples/qml/referenceexamples/binding/main.cpp
@@ -64,14 +64,14 @@ int main(int argc, char ** argv)
     auto *party = qobject_cast<BirthdayParty *>(component.create());
 
     if (party && party->host()) {
-        qWarning() << party->host()->name() << "is having a birthday!";
+        qInfo() << party->host()->name() << "is having a birthday!";
 
         if (qobject_cast<Boy *>(party->host()))
-            qWarning() << "He is inviting:";
+            qInfo() << "He is inviting:";
         else
-            qWarning() << "She is inviting:";
+            qInfo() << "She is inviting:";
 
-        for (int ii = 0; ii < party->guestCount(); ++ii) {
+        for (qsizetype ii = 0; ii < party->guestCount(); ++ii) {
             Person *guest = party->guest(ii);
 
             QDate rsvpDate;
@@ -81,9 +81,9 @@ int main(int argc, char ** argv)
                 rsvpDate = attached->property("rsvp").toDate();
 
             if (rsvpDate.isNull())
-                qWarning() << "   " << guest->name() << "RSVP date: Hasn't RSVP'd";
+                qInfo() << "   " << guest->name() << "RSVP date: Hasn't RSVP'd";
             else
-                qWarning() << "   " << guest->name() << "RSVP date:" << qPrintable(rsvpDate.toString());
+                qInfo() << "   " << guest->name() << "RSVP date:" << rsvpDate.toString();
         }
 
         party->startParty();
diff --git a/examples/qml/referenceexamples/binding/person.cpp b/examples/qml/referenceexamples/binding/person.cpp
index 1a23d0a4f5..0296b0a7c6 100644
--- a/examples/qml/referenceexamples/binding/person.cpp
+++ b/examples/qml/referenceexamples/binding/person.cpp
@@ -1,6 +1,6 @@
 /****************************************************************************
 **
-** Copyright (C) 2017 The Qt Company Ltd.
+** Copyright (C) 2021 The Qt Company Ltd.
 ** Contact: https://www.qt.io/licensing/
 **
 ** This file is part of the examples of the Qt Toolkit.
@@ -47,12 +47,8 @@
 ** $QT_END_LICENSE$
 **
 ****************************************************************************/
-#include "person.h"
 
-ShoeDescription::ShoeDescription(QObject *parent)
-: QObject(parent), m_size(0), m_price(0)
-{
-}
+#include "person.h"
 
 int ShoeDescription::size() const
 {
@@ -110,11 +106,6 @@ void ShoeDescription::setPrice(qreal p)
     emit shoeChanged();
 }
 
-Person::Person(QObject *parent)
-: QObject(parent)
-{
-}
-
 QString Person::name() const
 {
     return m_name;
@@ -133,16 +124,3 @@ ShoeDescription *Person::shoe()
 {
     return &m_shoe;
 }
-
-
-Boy::Boy(QObject * parent)
-: Person(parent)
-{
-}
-
-
-Girl::Girl(QObject * parent)
-: Person(parent)
-{
-}
-
diff --git a/examples/qml/referenceexamples/binding/person.h b/examples/qml/referenceexamples/binding/person.h
index af9864950a..e84075bb36 100644
--- a/examples/qml/referenceexamples/binding/person.h
+++ b/examples/qml/referenceexamples/binding/person.h
@@ -1,6 +1,6 @@
 /****************************************************************************
 **
-** Copyright (C) 2017 The Qt Company Ltd.
+** Copyright (C) 2021 The Qt Company Ltd.
 ** Contact: https://www.qt.io/licensing/
 **
 ** This file is part of the examples of the Qt Toolkit.
@@ -47,6 +47,7 @@
 ** $QT_END_LICENSE$
 **
 ****************************************************************************/
+
 #ifndef PERSON_H
 #define PERSON_H
 
@@ -63,7 +64,7 @@ class ShoeDescription : public QObject
     Q_PROPERTY(qreal price READ price WRITE setPrice NOTIFY shoeChanged)
     QML_ANONYMOUS
 public:
-    ShoeDescription(QObject *parent = nullptr);
+    using QObject::QObject;
 
     int size() const;
     void setSize(int);
@@ -76,14 +77,15 @@ public:
 
     qreal price() const;
     void setPrice(qreal);
+
 signals:
     void shoeChanged();
 
 private:
-    int m_size;
+    int m_size = 0;
     QColor m_color;
     QString m_brand;
-    qreal m_price;
+    qreal m_price = 0;
 };
 
 class Person : public QObject
@@ -95,12 +97,13 @@ class Person : public QObject
 // ![0]
     QML_ANONYMOUS
 public:
-    Person(QObject *parent = nullptr);
+    using QObject::QObject;
 
     QString name() const;
     void setName(const QString &);
 
     ShoeDescription *shoe();
+
 signals:
     void nameChanged();
 
@@ -114,7 +117,7 @@ class Boy : public Person
     Q_OBJECT
     QML_ELEMENT
 public:
-    Boy(QObject * parent = nullptr);
+    using Person::Person;
 };
 
 class Girl : public Person
@@ -122,7 +125,7 @@ class Girl : public Person
     Q_OBJECT
     QML_ELEMENT
 public:
-    Girl(QObject * parent = nullptr);
+    using Person::Person;
 };
 
 #endif // PERSON_H
diff --git a/examples/qml/referenceexamples/coercion/birthdayparty.cpp b/examples/qml/referenceexamples/coercion/birthdayparty.cpp
index 81db8ab1b8..269f45e02c 100644
--- a/examples/qml/referenceexamples/coercion/birthdayparty.cpp
+++ b/examples/qml/referenceexamples/coercion/birthdayparty.cpp
@@ -1,6 +1,6 @@
 /****************************************************************************
 **
-** Copyright (C) 2017 The Qt Company Ltd.
+** Copyright (C) 2021 The Qt Company Ltd.
 ** Contact: https://www.qt.io/licensing/
 **
 ** This file is part of the examples of the Qt Toolkit.
@@ -47,12 +47,8 @@
 ** $QT_END_LICENSE$
 **
 ****************************************************************************/
-#include "birthdayparty.h"
 
-BirthdayParty::BirthdayParty(QObject *parent)
-: QObject(parent), m_host(nullptr)
-{
-}
+#include "birthdayparty.h"
 
 Person *BirthdayParty::host() const
 {
@@ -69,13 +65,12 @@ QQmlListProperty<Person> BirthdayParty::guests()
     return {this, &m_guests};
 }
 
-int BirthdayParty::guestCount() const
+qsizetype BirthdayParty::guestCount() const
 {
     return m_guests.count();
 }
 
-Person *BirthdayParty::guest(int index) const
+Person *BirthdayParty::guest(qsizetype index) const
 {
     return m_guests.at(index);
 }
-
diff --git a/examples/qml/referenceexamples/coercion/birthdayparty.h b/examples/qml/referenceexamples/coercion/birthdayparty.h
index ba8b2445f1..a504479e4d 100644
--- a/examples/qml/referenceexamples/coercion/birthdayparty.h
+++ b/examples/qml/referenceexamples/coercion/birthdayparty.h
@@ -1,6 +1,6 @@
 /****************************************************************************
 **
-** Copyright (C) 2017 The Qt Company Ltd.
+** Copyright (C) 2021 The Qt Company Ltd.
 ** Contact: https://www.qt.io/licensing/
 **
 ** This file is part of the examples of the Qt Toolkit.
@@ -47,6 +47,7 @@
 ** $QT_END_LICENSE$
 **
 ****************************************************************************/
+
 #ifndef BIRTHDAYPARTY_H
 #define BIRTHDAYPARTY_H
 
@@ -63,17 +64,17 @@ class BirthdayParty : public QObject
     QML_ELEMENT
 // ![0]
 public:
-    BirthdayParty(QObject *parent = nullptr);
+    using QObject::QObject;
 
     Person *host() const;
     void setHost(Person *);
 
     QQmlListProperty<Person> guests();
-    int guestCount() const;
-    Person *guest(int) const;
+    qsizetype guestCount() const;
+    Person *guest(qsizetype) const;
 
 private:
-    Person *m_host;
+    Person *m_host = nullptr;
     QList<Person *> m_guests;
 };
 
diff --git a/examples/qml/referenceexamples/coercion/main.cpp b/examples/qml/referenceexamples/coercion/main.cpp
index 6b47d0d4c4..095602af9d 100644
--- a/examples/qml/referenceexamples/coercion/main.cpp
+++ b/examples/qml/referenceexamples/coercion/main.cpp
@@ -1,6 +1,6 @@
 /****************************************************************************
 **
-** Copyright (C) 2017 The Qt Company Ltd.
+** Copyright (C) 2021 The Qt Company Ltd.
 ** Contact: https://www.qt.io/licensing/
 **
 ** This file is part of the examples of the Qt Toolkit.
@@ -47,6 +47,7 @@
 ** $QT_END_LICENSE$
 **
 ****************************************************************************/
+
 #include <QCoreApplication>
 #include <QQmlEngine>
 #include <QQmlComponent>
@@ -63,15 +64,15 @@ int main(int argc, char ** argv)
     auto *party = qobject_cast<BirthdayParty *>(component.create());
 
     if (party && party->host()) {
-        qWarning() << party->host()->name() << "is having a birthday!";
+        qInfo() << party->host()->name() << "is having a birthday!";
 
         if (qobject_cast<Boy *>(party->host()))
-            qWarning() << "He is inviting:";
+            qInfo() << "He is inviting:";
         else
-            qWarning() << "She is inviting:";
+            qInfo() << "She is inviting:";
 
-        for (int ii = 0; ii < party->guestCount(); ++ii)
-            qWarning() << "   " << party->guest(ii)->name();
+        for (qsizetype ii = 0; ii < party->guestCount(); ++ii)
+            qInfo() << "   " << party->guest(ii)->name();
 
         return EXIT_SUCCESS;
     }
diff --git a/examples/qml/referenceexamples/coercion/person.cpp b/examples/qml/referenceexamples/coercion/person.cpp
index 178d7052ce..e2847a2682 100644
--- a/examples/qml/referenceexamples/coercion/person.cpp
+++ b/examples/qml/referenceexamples/coercion/person.cpp
@@ -1,6 +1,6 @@
 /****************************************************************************
 **
-** Copyright (C) 2017 The Qt Company Ltd.
+** Copyright (C) 2021 The Qt Company Ltd.
 ** Contact: https://www.qt.io/licensing/
 **
 ** This file is part of the examples of the Qt Toolkit.
@@ -47,12 +47,8 @@
 ** $QT_END_LICENSE$
 **
 ****************************************************************************/
-#include "person.h"
 
-Person::Person(QObject *parent)
-: QObject(parent), m_shoeSize(0)
-{
-}
+#include "person.h"
 
 QString Person::name() const
 {
@@ -73,17 +69,3 @@ void Person::setShoeSize(int s)
 {
     m_shoeSize = s;
 }
-
-// ![1]
-Boy::Boy(QObject * parent)
-: Person(parent)
-{
-}
-
-
-Girl::Girl(QObject * parent)
-: Person(parent)
-{
-}
-
-// ![1]
diff --git a/examples/qml/referenceexamples/coercion/person.h b/examples/qml/referenceexamples/coercion/person.h
index 7e2828da04..1ec095e841 100644
--- a/examples/qml/referenceexamples/coercion/person.h
+++ b/examples/qml/referenceexamples/coercion/person.h
@@ -1,6 +1,6 @@
 /****************************************************************************
 **
-** Copyright (C) 2017 The Qt Company Ltd.
+** Copyright (C) 2021 The Qt Company Ltd.
 ** Contact: https://www.qt.io/licensing/
 **
 ** This file is part of the examples of the Qt Toolkit.
@@ -47,6 +47,7 @@
 ** $QT_END_LICENSE$
 **
 ****************************************************************************/
+
 #ifndef PERSON_H
 #define PERSON_H
 
@@ -63,16 +64,17 @@ class Person : public QObject
     QML_UNCREATABLE("Person is an abstract base class.")
     //![0]
 public:
-    Person(QObject *parent = nullptr);
+    using QObject::QObject;
 
     QString name() const;
     void setName(const QString &);
 
     int shoeSize() const;
     void setShoeSize(int);
+
 private:
     QString m_name;
-    int m_shoeSize;
+    int m_shoeSize = 0;
 };
 
 
@@ -82,7 +84,7 @@ class Boy : public Person
     Q_OBJECT
     QML_ELEMENT
 public:
-    Boy(QObject * parent = nullptr);
+    using Person::Person;
 };
 
 //! [girl class]
@@ -91,7 +93,7 @@ class Girl : public Person
     Q_OBJECT
     QML_ELEMENT
 public:
-    Girl(QObject * parent = nullptr);
+    using Person::Person;
 };
 //! [girl class]
 
diff --git a/examples/qml/referenceexamples/default/birthdayparty.cpp b/examples/qml/referenceexamples/default/birthdayparty.cpp
index 81db8ab1b8..aeaf6fbd9c 100644
--- a/examples/qml/referenceexamples/default/birthdayparty.cpp
+++ b/examples/qml/referenceexamples/default/birthdayparty.cpp
@@ -1,6 +1,6 @@
 /****************************************************************************
 **
-** Copyright (C) 2017 The Qt Company Ltd.
+** Copyright (C) 2021 The Qt Company Ltd.
 ** Contact: https://www.qt.io/licensing/
 **
 ** This file is part of the examples of the Qt Toolkit.
@@ -47,12 +47,8 @@
 ** $QT_END_LICENSE$
 **
 ****************************************************************************/
-#include "birthdayparty.h"
 
-BirthdayParty::BirthdayParty(QObject *parent)
-: QObject(parent), m_host(nullptr)
-{
-}
+#include "birthdayparty.h"
 
 Person *BirthdayParty::host() const
 {
@@ -69,12 +65,12 @@ QQmlListProperty<Person> BirthdayParty::guests()
     return {this, &m_guests};
 }
 
-int BirthdayParty::guestCount() const
+qsizetype BirthdayParty::guestCount() const
 {
     return m_guests.count();
 }
 
-Person *BirthdayParty::guest(int index) const
+Person *BirthdayParty::guest(qsizetype index) const
 {
     return m_guests.at(index);
 }
diff --git a/examples/qml/referenceexamples/default/birthdayparty.h b/examples/qml/referenceexamples/default/birthdayparty.h
index 5eb6c88763..cb12a1510b 100644
--- a/examples/qml/referenceexamples/default/birthdayparty.h
+++ b/examples/qml/referenceexamples/default/birthdayparty.h
@@ -1,6 +1,6 @@
 /****************************************************************************
 **
-** Copyright (C) 2017 The Qt Company Ltd.
+** Copyright (C) 2021 The Qt Company Ltd.
 ** Contact: https://www.qt.io/licensing/
 **
 ** This file is part of the examples of the Qt Toolkit.
@@ -47,6 +47,7 @@
 ** $QT_END_LICENSE$
 **
 ****************************************************************************/
+
 #ifndef BIRTHDAYPARTY_H
 #define BIRTHDAYPARTY_H
 
@@ -63,17 +64,17 @@ class BirthdayParty : public QObject
     Q_CLASSINFO("DefaultProperty", "guests")
     QML_ELEMENT
 public:
-    BirthdayParty(QObject *parent = nullptr);
+    using QObject::QObject;
 
     Person *host() const;
     void setHost(Person *);
 
     QQmlListProperty<Person> guests();
-    int guestCount() const;
-    Person *guest(int) const;
+    qsizetype guestCount() const;
+    Person *guest(qsizetype) const;
 
 private:
-    Person *m_host;
+    Person *m_host = nullptr;
     QList<Person *> m_guests;
 };
 // ![0]
diff --git a/examples/qml/referenceexamples/default/main.cpp b/examples/qml/referenceexamples/default/main.cpp
index 6b47d0d4c4..82e6f5ba37 100644
--- a/examples/qml/referenceexamples/default/main.cpp
+++ b/examples/qml/referenceexamples/default/main.cpp
@@ -63,15 +63,15 @@ int main(int argc, char ** argv)
     auto *party = qobject_cast<BirthdayParty *>(component.create());
 
     if (party && party->host()) {
-        qWarning() << party->host()->name() << "is having a birthday!";
+        qInfo() << party->host()->name() << "is having a birthday!";
 
         if (qobject_cast<Boy *>(party->host()))
-            qWarning() << "He is inviting:";
+            qInfo() << "He is inviting:";
         else
-            qWarning() << "She is inviting:";
+            qInfo() << "She is inviting:";
 
-        for (int ii = 0; ii < party->guestCount(); ++ii)
-            qWarning() << "   " << party->guest(ii)->name();
+        for (qsizetype ii = 0; ii < party->guestCount(); ++ii)
+            qInfo() << "   " << party->guest(ii)->name();
 
         return EXIT_SUCCESS;
     }
diff --git a/examples/qml/referenceexamples/default/person.cpp b/examples/qml/referenceexamples/default/person.cpp
index a1d887a4d0..e2847a2682 100644
--- a/examples/qml/referenceexamples/default/person.cpp
+++ b/examples/qml/referenceexamples/default/person.cpp
@@ -1,6 +1,6 @@
 /****************************************************************************
 **
-** Copyright (C) 2017 The Qt Company Ltd.
+** Copyright (C) 2021 The Qt Company Ltd.
 ** Contact: https://www.qt.io/licensing/
 **
 ** This file is part of the examples of the Qt Toolkit.
@@ -47,12 +47,8 @@
 ** $QT_END_LICENSE$
 **
 ****************************************************************************/
-#include "person.h"
 
-Person::Person(QObject *parent)
-: QObject(parent), m_shoeSize(0)
-{
-}
+#include "person.h"
 
 QString Person::name() const
 {
@@ -73,16 +69,3 @@ void Person::setShoeSize(int s)
 {
     m_shoeSize = s;
 }
-
-
-Boy::Boy(QObject * parent)
-: Person(parent)
-{
-}
-
-
-Girl::Girl(QObject * parent)
-: Person(parent)
-{
-}
-
diff --git a/examples/qml/referenceexamples/default/person.h b/examples/qml/referenceexamples/default/person.h
index 361a89c599..0b2e280747 100644
--- a/examples/qml/referenceexamples/default/person.h
+++ b/examples/qml/referenceexamples/default/person.h
@@ -1,6 +1,6 @@
 /****************************************************************************
 **
-** Copyright (C) 2017 The Qt Company Ltd.
+** Copyright (C) 2021 The Qt Company Ltd.
 ** Contact: https://www.qt.io/licensing/
 **
 ** This file is part of the examples of the Qt Toolkit.
@@ -47,6 +47,7 @@
 ** $QT_END_LICENSE$
 **
 ****************************************************************************/
+
 #ifndef PERSON_H
 #define PERSON_H
 
@@ -60,7 +61,7 @@ class Person : public QObject
     Q_PROPERTY(int shoeSize READ shoeSize WRITE setShoeSize)
     QML_ANONYMOUS
 public:
-    Person(QObject *parent = nullptr);
+    using QObject::QObject;
 
     QString name() const;
     void setName(const QString &);
@@ -69,7 +70,7 @@ public:
     void setShoeSize(int);
 private:
     QString m_name;
-    int m_shoeSize;
+    int m_shoeSize = 0;
 };
 
 class Boy : public Person
@@ -77,7 +78,7 @@ class Boy : public Person
     Q_OBJECT
     QML_ELEMENT
 public:
-    Boy(QObject * parent = nullptr);
+    using Person::Person;
 };
 
 class Girl : public Person
@@ -85,7 +86,7 @@ class Girl : public Person
     Q_OBJECT
     QML_ELEMENT
 public:
-    Girl(QObject * parent = nullptr);
+    using Person::Person;
 };
 
 #endif // PERSON_H
diff --git a/examples/qml/referenceexamples/grouped/birthdayparty.cpp b/examples/qml/referenceexamples/grouped/birthdayparty.cpp
index 81db8ab1b8..269f45e02c 100644
--- a/examples/qml/referenceexamples/grouped/birthdayparty.cpp
+++ b/examples/qml/referenceexamples/grouped/birthdayparty.cpp
@@ -1,6 +1,6 @@
 /****************************************************************************
 **
-** Copyright (C) 2017 The Qt Company Ltd.
+** Copyright (C) 2021 The Qt Company Ltd.
 ** Contact: https://www.qt.io/licensing/
 **
 ** This file is part of the examples of the Qt Toolkit.
@@ -47,12 +47,8 @@
 ** $QT_END_LICENSE$
 **
 ****************************************************************************/
-#include "birthdayparty.h"
 
-BirthdayParty::BirthdayParty(QObject *parent)
-: QObject(parent), m_host(nullptr)
-{
-}
+#include "birthdayparty.h"
 
 Person *BirthdayParty::host() const
 {
@@ -69,13 +65,12 @@ QQmlListProperty<Person> BirthdayParty::guests()
     return {this, &m_guests};
 }
 
-int BirthdayParty::guestCount() const
+qsizetype BirthdayParty::guestCount() const
 {
     return m_guests.count();
 }
 
-Person *BirthdayParty::guest(int index) const
+Person *BirthdayParty::guest(qsizetype index) const
 {
     return m_guests.at(index);
 }
-
diff --git a/examples/qml/referenceexamples/grouped/birthdayparty.h b/examples/qml/referenceexamples/grouped/birthdayparty.h
index f6834dad89..a8e0964365 100644
--- a/examples/qml/referenceexamples/grouped/birthdayparty.h
+++ b/examples/qml/referenceexamples/grouped/birthdayparty.h
@@ -1,6 +1,6 @@
 /****************************************************************************
 **
-** Copyright (C) 2017 The Qt Company Ltd.
+** Copyright (C) 2021 The Qt Company Ltd.
 ** Contact: https://www.qt.io/licensing/
 **
 ** This file is part of the examples of the Qt Toolkit.
@@ -47,6 +47,7 @@
 ** $QT_END_LICENSE$
 **
 ****************************************************************************/
+
 #ifndef BIRTHDAYPARTY_H
 #define BIRTHDAYPARTY_H
 
@@ -62,14 +63,14 @@ class BirthdayParty : public QObject
     Q_CLASSINFO("DefaultProperty", "guests")
     QML_ELEMENT
 public:
-    BirthdayParty(QObject *parent = nullptr);
+    using QObject::QObject;
 
     Person *host() const;
     void setHost(Person *);
 
     QQmlListProperty<Person> guests();
-    int guestCount() const;
-    Person *guest(int) const;
+    qsizetype guestCount() const;
+    Person *guest(qsizetype) const;
 
 private:
     Person *m_host;
diff --git a/examples/qml/referenceexamples/grouped/main.cpp b/examples/qml/referenceexamples/grouped/main.cpp
index 63dbe988a4..6d4ec517cc 100644
--- a/examples/qml/referenceexamples/grouped/main.cpp
+++ b/examples/qml/referenceexamples/grouped/main.cpp
@@ -63,23 +63,23 @@ int main(int argc, char ** argv)
     auto *party = qobject_cast<BirthdayParty *>(component.create());
 
     if (party && party->host()) {
-        qWarning() << party->host()->name() << "is having a birthday!";
+        qInfo() << party->host()->name() << "is having a birthday!";
 
         if (qobject_cast<Boy *>(party->host()))
-            qWarning() << "He is inviting:";
+            qInfo() << "He is inviting:";
         else
-            qWarning() << "She is inviting:";
+            qInfo() << "She is inviting:";
 
         Person *bestShoe = nullptr;
-        for (int ii = 0; ii < party->guestCount(); ++ii) {
+        for (qsizetype ii = 0; ii < party->guestCount(); ++ii) {
             Person *guest = party->guest(ii);
-            qWarning() << "   " << guest->name();
+            qInfo() << "   " << guest->name();
 
             if (!bestShoe || bestShoe->shoe()->price() < guest->shoe()->price())
                 bestShoe = guest;
         }
         if (bestShoe)
-            qWarning() << bestShoe->name() << "is wearing the best shoes!";
+            qInfo() << bestShoe->name() << "is wearing the best shoes!";
 
         return EXIT_SUCCESS;
     }
diff --git a/examples/qml/referenceexamples/grouped/person.cpp b/examples/qml/referenceexamples/grouped/person.cpp
index 0603644108..4e52da76c8 100644
--- a/examples/qml/referenceexamples/grouped/person.cpp
+++ b/examples/qml/referenceexamples/grouped/person.cpp
@@ -1,6 +1,6 @@
 /****************************************************************************
 **
-** Copyright (C) 2017 The Qt Company Ltd.
+** Copyright (C) 2021 The Qt Company Ltd.
 ** Contact: https://www.qt.io/licensing/
 **
 ** This file is part of the examples of the Qt Toolkit.
@@ -47,12 +47,8 @@
 ** $QT_END_LICENSE$
 **
 ****************************************************************************/
-#include "person.h"
 
-ShoeDescription::ShoeDescription(QObject *parent)
-: QObject(parent), m_size(0), m_price(0)
-{
-}
+#include "person.h"
 
 int ShoeDescription::size() const
 {
@@ -94,11 +90,6 @@ void ShoeDescription::setPrice(qreal p)
     m_price = p;
 }
 
-Person::Person(QObject *parent)
-: QObject(parent)
-{
-}
-
 QString Person::name() const
 {
     return m_name;
@@ -113,16 +104,3 @@ ShoeDescription *Person::shoe()
 {
     return &m_shoe;
 }
-
-
-Boy::Boy(QObject * parent)
-: Person(parent)
-{
-}
-
-
-Girl::Girl(QObject * parent)
-: Person(parent)
-{
-}
-
diff --git a/examples/qml/referenceexamples/grouped/person.h b/examples/qml/referenceexamples/grouped/person.h
index df507c7386..ed77f8c4d8 100644
--- a/examples/qml/referenceexamples/grouped/person.h
+++ b/examples/qml/referenceexamples/grouped/person.h
@@ -1,6 +1,6 @@
 /****************************************************************************
 **
-** Copyright (C) 2017 The Qt Company Ltd.
+** Copyright (C) 2021 The Qt Company Ltd.
 ** Contact: https://www.qt.io/licensing/
 **
 ** This file is part of the examples of the Qt Toolkit.
@@ -47,6 +47,7 @@
 ** $QT_END_LICENSE$
 **
 ****************************************************************************/
+
 #ifndef PERSON_H
 #define PERSON_H
 
@@ -63,7 +64,7 @@ class ShoeDescription : public QObject
     Q_PROPERTY(qreal price READ price WRITE setPrice)
     QML_ANONYMOUS
 public:
-    ShoeDescription(QObject *parent = nullptr);
+    using QObject::QObject;
 
     int size() const;
     void setSize(int);
@@ -76,11 +77,12 @@ public:
 
     qreal price() const;
     void setPrice(qreal);
+
 private:
-    int m_size;
+    int m_size = 0;
     QColor m_color;
     QString m_brand;
-    qreal m_price;
+    qreal m_price = 0;
 };
 
 class Person : public QObject
@@ -92,7 +94,7 @@ class Person : public QObject
 // ![1]
     QML_ANONYMOUS
 public:
-    Person(QObject *parent = nullptr);
+    using QObject::QObject;
 
     QString name() const;
     void setName(const QString &);
@@ -108,7 +110,7 @@ class Boy : public Person
     Q_OBJECT
     QML_ELEMENT
 public:
-    Boy(QObject * parent = nullptr);
+    using Person::Person;
 };
 
 class Girl : public Person
@@ -116,7 +118,7 @@ class Girl : public Person
     Q_OBJECT
     QML_ELEMENT
 public:
-    Girl(QObject * parent = nullptr);
+    using Person::Person;
 };
 
 #endif // PERSON_H
diff --git a/examples/qml/referenceexamples/methods/birthdayparty.cpp b/examples/qml/referenceexamples/methods/birthdayparty.cpp
index 4b30d31aeb..1308a09b72 100644
--- a/examples/qml/referenceexamples/methods/birthdayparty.cpp
+++ b/examples/qml/referenceexamples/methods/birthdayparty.cpp
@@ -1,6 +1,6 @@
 /****************************************************************************
 **
-** Copyright (C) 2017 The Qt Company Ltd.
+** Copyright (C) 2021 The Qt Company Ltd.
 ** Contact: https://www.qt.io/licensing/
 **
 ** This file is part of the examples of the Qt Toolkit.
@@ -47,12 +47,8 @@
 ** $QT_END_LICENSE$
 **
 ****************************************************************************/
-#include "birthdayparty.h"
 
-BirthdayParty::BirthdayParty(QObject *parent)
-: QObject(parent), m_host(nullptr)
-{
-}
+#include "birthdayparty.h"
 
 // ![0]
 Person *BirthdayParty::host() const
@@ -70,12 +66,12 @@ QQmlListProperty<Person> BirthdayParty::guests()
     return {this, &m_guests};
 }
 
-int BirthdayParty::guestCount() const
+qsizetype BirthdayParty::guestCount() const
 {
     return m_guests.count();
 }
 
-Person *BirthdayParty::guest(int index) const
+Person *BirthdayParty::guest(qsizetype index) const
 {
     return m_guests.at(index);
 }
diff --git a/examples/qml/referenceexamples/methods/birthdayparty.h b/examples/qml/referenceexamples/methods/birthdayparty.h
index 5c2f3c9def..b43308ac8f 100644
--- a/examples/qml/referenceexamples/methods/birthdayparty.h
+++ b/examples/qml/referenceexamples/methods/birthdayparty.h
@@ -1,6 +1,6 @@
 /****************************************************************************
 **
-** Copyright (C) 2017 The Qt Company Ltd.
+** Copyright (C) 2021 The Qt Company Ltd.
 ** Contact: https://www.qt.io/licensing/
 **
 ** This file is part of the examples of the Qt Toolkit.
@@ -47,6 +47,7 @@
 ** $QT_END_LICENSE$
 **
 ****************************************************************************/
+
 #ifndef BIRTHDAYPARTY_H
 #define BIRTHDAYPARTY_H
 
@@ -61,21 +62,21 @@ class BirthdayParty : public QObject
     Q_PROPERTY(QQmlListProperty<Person> guests READ guests)
     QML_ELEMENT
 public:
-    BirthdayParty(QObject *parent = nullptr);
+    using QObject::QObject;
 
     Person *host() const;
     void setHost(Person *);
 
     QQmlListProperty<Person> guests();
-    int guestCount() const;
-    Person *guest(int) const;
+    qsizetype guestCount() const;
+    Person *guest(qsizetype) const;
 
 // ![0]
     Q_INVOKABLE void invite(const QString &name);
 // ![0]
 
 private:
-    Person *m_host;
+    Person *m_host = nullptr;
     QList<Person *> m_guests;
 };
 
diff --git a/examples/qml/referenceexamples/methods/main.cpp b/examples/qml/referenceexamples/methods/main.cpp
index e30e1d9fb1..32eb4831cc 100644
--- a/examples/qml/referenceexamples/methods/main.cpp
+++ b/examples/qml/referenceexamples/methods/main.cpp
@@ -1,6 +1,6 @@
 /****************************************************************************
 **
-** Copyright (C) 2017 The Qt Company Ltd.
+** Copyright (C) 2021 The Qt Company Ltd.
 ** Contact: https://www.qt.io/licensing/
 **
 ** This file is part of the examples of the Qt Toolkit.
@@ -47,6 +47,7 @@
 ** $QT_END_LICENSE$
 **
 ****************************************************************************/
+
 #include <QCoreApplication>
 #include <QQmlEngine>
 #include <QQmlComponent>
@@ -63,10 +64,10 @@ int main(int argc, char ** argv)
     auto *party = qobject_cast<BirthdayParty *>(component.create());
 
     if (party && party->host()) {
-        qWarning() << party->host()->name() << "is having a birthday!";
-        qWarning() << "They are inviting:";
-        for (int ii = 0; ii < party->guestCount(); ++ii)
-            qWarning() << "   " << party->guest(ii)->name();
+        qInfo() << party->host()->name() << "is having a birthday!"
+            << "\nThey are inviting:";
+        for (qsizetype ii = 0; ii < party->guestCount(); ++ii)
+            qInfo() << "   " << party->guest(ii)->name();
         return EXIT_SUCCESS;
     }
 
diff --git a/examples/qml/referenceexamples/methods/person.cpp b/examples/qml/referenceexamples/methods/person.cpp
index 7712363ebf..e2847a2682 100644
--- a/examples/qml/referenceexamples/methods/person.cpp
+++ b/examples/qml/referenceexamples/methods/person.cpp
@@ -1,6 +1,6 @@
 /****************************************************************************
 **
-** Copyright (C) 2017 The Qt Company Ltd.
+** Copyright (C) 2021 The Qt Company Ltd.
 ** Contact: https://www.qt.io/licensing/
 **
 ** This file is part of the examples of the Qt Toolkit.
@@ -47,12 +47,8 @@
 ** $QT_END_LICENSE$
 **
 ****************************************************************************/
-#include "person.h"
 
-Person::Person(QObject *parent)
-: QObject(parent), m_shoeSize(0)
-{
-}
+#include "person.h"
 
 QString Person::name() const
 {
@@ -73,4 +69,3 @@ void Person::setShoeSize(int s)
 {
     m_shoeSize = s;
 }
-
diff --git a/examples/qml/referenceexamples/methods/person.h b/examples/qml/referenceexamples/methods/person.h
index 2407fbb1b9..0849d1ee8c 100644
--- a/examples/qml/referenceexamples/methods/person.h
+++ b/examples/qml/referenceexamples/methods/person.h
@@ -1,6 +1,6 @@
 /****************************************************************************
 **
-** Copyright (C) 2017 The Qt Company Ltd.
+** Copyright (C) 2021 The Qt Company Ltd.
 ** Contact: https://www.qt.io/licensing/
 **
 ** This file is part of the examples of the Qt Toolkit.
@@ -47,6 +47,7 @@
 ** $QT_END_LICENSE$
 **
 ****************************************************************************/
+
 #ifndef PERSON_H
 #define PERSON_H
 
@@ -60,16 +61,17 @@ class Person : public QObject
     Q_PROPERTY(int shoeSize READ shoeSize WRITE setShoeSize)
     QML_ELEMENT
 public:
-    Person(QObject *parent = nullptr);
+    using QObject::QObject;
 
     QString name() const;
     void setName(const QString &);
 
     int shoeSize() const;
     void setShoeSize(int);
+
 private:
     QString m_name;
-    int m_shoeSize;
+    int m_shoeSize = 0;
 };
 
 #endif // PERSON_H
diff --git a/examples/qml/referenceexamples/properties/birthdayparty.cpp b/examples/qml/referenceexamples/properties/birthdayparty.cpp
index 2dc9bd803d..aca626db74 100644
--- a/examples/qml/referenceexamples/properties/birthdayparty.cpp
+++ b/examples/qml/referenceexamples/properties/birthdayparty.cpp
@@ -1,6 +1,6 @@
 /****************************************************************************
 **
-** Copyright (C) 2017 The Qt Company Ltd.
+** Copyright (C) 2021 The Qt Company Ltd.
 ** Contact: https://www.qt.io/licensing/
 **
 ** This file is part of the examples of the Qt Toolkit.
@@ -47,12 +47,8 @@
 ** $QT_END_LICENSE$
 **
 ****************************************************************************/
-#include "birthdayparty.h"
 
-BirthdayParty::BirthdayParty(QObject *parent)
-: QObject(parent), m_host(nullptr)
-{
-}
+#include "birthdayparty.h"
 
 // ![0]
 Person *BirthdayParty::host() const
@@ -76,11 +72,11 @@ QQmlListProperty<Person> BirthdayParty::guests()
              &BirthdayParty::removeLastGuest};
 }
 
-void BirthdayParty::appendGuest(Person* p) {
+void BirthdayParty::appendGuest(Person *p)
+{
     m_guests.append(p);
 }
 
-
 qsizetype BirthdayParty::guestCount() const
 {
     return m_guests.count();
@@ -107,12 +103,14 @@ void BirthdayParty::removeLastGuest()
 
 // ![0]
 
-void BirthdayParty::appendGuest(QQmlListProperty<Person>* list, Person* p) {
-    reinterpret_cast< BirthdayParty* >(list->data)->appendGuest(p);
+void BirthdayParty::appendGuest(QQmlListProperty<Person> *list, Person *p)
+{
+    reinterpret_cast< BirthdayParty *>(list->data)->appendGuest(p);
 }
 
-void BirthdayParty::clearGuests(QQmlListProperty<Person>* list) {
-    reinterpret_cast< BirthdayParty* >(list->data)->clearGuests();
+void BirthdayParty::clearGuests(QQmlListProperty<Person>* list)
+{
+    reinterpret_cast< BirthdayParty *>(list->data)->clearGuests();
 }
 
 void BirthdayParty::replaceGuest(QQmlListProperty<Person> *list, qsizetype i, Person *p)
@@ -125,10 +123,12 @@ void BirthdayParty::removeLastGuest(QQmlListProperty<Person> *list)
     reinterpret_cast< BirthdayParty* >(list->data)->removeLastGuest();
 }
 
-Person* BirthdayParty::guest(QQmlListProperty<Person>* list, qsizetype i) {
+Person* BirthdayParty::guest(QQmlListProperty<Person> *list, qsizetype i)
+{
     return reinterpret_cast< BirthdayParty* >(list->data)->guest(i);
 }
 
-qsizetype BirthdayParty::guestCount(QQmlListProperty<Person>* list) {
+qsizetype BirthdayParty::guestCount(QQmlListProperty<Person> *list)
+{
     return reinterpret_cast< BirthdayParty* >(list->data)->guestCount();
 }
diff --git a/examples/qml/referenceexamples/properties/birthdayparty.h b/examples/qml/referenceexamples/properties/birthdayparty.h
index 7e1668add3..278c011d11 100644
--- a/examples/qml/referenceexamples/properties/birthdayparty.h
+++ b/examples/qml/referenceexamples/properties/birthdayparty.h
@@ -1,6 +1,6 @@
 /****************************************************************************
 **
-** Copyright (C) 2017 The Qt Company Ltd.
+** Copyright (C) 2021 The Qt Company Ltd.
 ** Contact: https://www.qt.io/licensing/
 **
 ** This file is part of the examples of the Qt Toolkit.
@@ -47,6 +47,7 @@
 ** $QT_END_LICENSE$
 **
 ****************************************************************************/
+
 #ifndef BIRTHDAYPARTY_H
 #define BIRTHDAYPARTY_H
 
@@ -69,28 +70,28 @@ class BirthdayParty : public QObject
 // ![3]
     QML_ELEMENT
 public:
-    BirthdayParty(QObject *parent = nullptr);
+    using QObject::QObject;
 
     Person *host() const;
     void setHost(Person *);
 
     QQmlListProperty<Person> guests();
-    void appendGuest(Person*);
+    void appendGuest(Person *);
     qsizetype guestCount() const;
     Person *guest(qsizetype) const;
     void clearGuests();
-    void replaceGuest(qsizetype, Person*);
+    void replaceGuest(qsizetype, Person *);
     void removeLastGuest();
 
 private:
-    static void appendGuest(QQmlListProperty<Person>*, Person*);
-    static qsizetype guestCount(QQmlListProperty<Person>*);
-    static Person* guest(QQmlListProperty<Person>*, qsizetype);
-    static void clearGuests(QQmlListProperty<Person>*);
-    static void replaceGuest(QQmlListProperty<Person>*, qsizetype, Person*);
-    static void removeLastGuest(QQmlListProperty<Person>*);
+    static void appendGuest(QQmlListProperty<Person> *, Person *);
+    static qsizetype guestCount(QQmlListProperty<Person> *);
+    static Person* guest(QQmlListProperty<Person> *, qsizetype);
+    static void clearGuests(QQmlListProperty<Person> *);
+    static void replaceGuest(QQmlListProperty<Person> *, qsizetype, Person *);
+    static void removeLastGuest(QQmlListProperty<Person> *);
 
-    Person *m_host;
+    Person *m_host = nullptr;
     QList<Person *> m_guests;
 };
 // ![3]
diff --git a/examples/qml/referenceexamples/properties/main.cpp b/examples/qml/referenceexamples/properties/main.cpp
index e30e1d9fb1..cd71497002 100644
--- a/examples/qml/referenceexamples/properties/main.cpp
+++ b/examples/qml/referenceexamples/properties/main.cpp
@@ -63,10 +63,10 @@ int main(int argc, char ** argv)
     auto *party = qobject_cast<BirthdayParty *>(component.create());
 
     if (party && party->host()) {
-        qWarning() << party->host()->name() << "is having a birthday!";
-        qWarning() << "They are inviting:";
-        for (int ii = 0; ii < party->guestCount(); ++ii)
-            qWarning() << "   " << party->guest(ii)->name();
+        qInfo() << party->host()->name() << "is having a birthday!\n"
+            "They are inviting:";
+        for (qsizetype ii = 0; ii < party->guestCount(); ++ii)
+            qInfo() << "   " << party->guest(ii)->name();
         return EXIT_SUCCESS;
     }
 
diff --git a/examples/qml/referenceexamples/properties/person.cpp b/examples/qml/referenceexamples/properties/person.cpp
index 7712363ebf..e2847a2682 100644
--- a/examples/qml/referenceexamples/properties/person.cpp
+++ b/examples/qml/referenceexamples/properties/person.cpp
@@ -1,6 +1,6 @@
 /****************************************************************************
 **
-** Copyright (C) 2017 The Qt Company Ltd.
+** Copyright (C) 2021 The Qt Company Ltd.
 ** Contact: https://www.qt.io/licensing/
 **
 ** This file is part of the examples of the Qt Toolkit.
@@ -47,12 +47,8 @@
 ** $QT_END_LICENSE$
 **
 ****************************************************************************/
-#include "person.h"
 
-Person::Person(QObject *parent)
-: QObject(parent), m_shoeSize(0)
-{
-}
+#include "person.h"
 
 QString Person::name() const
 {
@@ -73,4 +69,3 @@ void Person::setShoeSize(int s)
 {
     m_shoeSize = s;
 }
-
diff --git a/examples/qml/referenceexamples/properties/person.h b/examples/qml/referenceexamples/properties/person.h
index 2407fbb1b9..0849d1ee8c 100644
--- a/examples/qml/referenceexamples/properties/person.h
+++ b/examples/qml/referenceexamples/properties/person.h
@@ -1,6 +1,6 @@
 /****************************************************************************
 **
-** Copyright (C) 2017 The Qt Company Ltd.
+** Copyright (C) 2021 The Qt Company Ltd.
 ** Contact: https://www.qt.io/licensing/
 **
 ** This file is part of the examples of the Qt Toolkit.
@@ -47,6 +47,7 @@
 ** $QT_END_LICENSE$
 **
 ****************************************************************************/
+
 #ifndef PERSON_H
 #define PERSON_H
 
@@ -60,16 +61,17 @@ class Person : public QObject
     Q_PROPERTY(int shoeSize READ shoeSize WRITE setShoeSize)
     QML_ELEMENT
 public:
-    Person(QObject *parent = nullptr);
+    using QObject::QObject;
 
     QString name() const;
     void setName(const QString &);
 
     int shoeSize() const;
     void setShoeSize(int);
+
 private:
     QString m_name;
-    int m_shoeSize;
+    int m_shoeSize = 0;
 };
 
 #endif // PERSON_H
diff --git a/examples/qml/referenceexamples/signal/birthdayparty.cpp b/examples/qml/referenceexamples/signal/birthdayparty.cpp
index 215c09782a..27498c9cc9 100644
--- a/examples/qml/referenceexamples/signal/birthdayparty.cpp
+++ b/examples/qml/referenceexamples/signal/birthdayparty.cpp
@@ -1,6 +1,6 @@
 /****************************************************************************
 **
-** Copyright (C) 2017 The Qt Company Ltd.
+** Copyright (C) 2021 The Qt Company Ltd.
 ** Contact: https://www.qt.io/licensing/
 **
 ** This file is part of the examples of the Qt Toolkit.
@@ -47,16 +47,12 @@
 ** $QT_END_LICENSE$
 **
 ****************************************************************************/
-#include "birthdayparty.h"
 
-BirthdayPartyAttached::BirthdayPartyAttached(QObject *object)
-: QObject(object)
-{
-}
+#include "birthdayparty.h"
 
 QDate BirthdayPartyAttached::rsvp() const
 {
-    return m_rsvp;
+   return m_rsvp;
 }
 
 void BirthdayPartyAttached::setRsvp(QDate d)
@@ -64,12 +60,6 @@ void BirthdayPartyAttached::setRsvp(QDate d)
     m_rsvp = d;
 }
 
-
-BirthdayParty::BirthdayParty(QObject *parent)
-: QObject(parent), m_host(nullptr)
-{
-}
-
 Person *BirthdayParty::host() const
 {
     return m_host;
@@ -85,12 +75,12 @@ QQmlListProperty<Person> BirthdayParty::guests()
     return {this, &m_guests};
 }
 
-int BirthdayParty::guestCount() const
+qsizetype BirthdayParty::guestCount() const
 {
     return m_guests.count();
 }
 
-Person *BirthdayParty::guest(int index) const
+Person *BirthdayParty::guest(qsizetype index) const
 {
     return m_guests.at(index);
 }
diff --git a/examples/qml/referenceexamples/signal/birthdayparty.h b/examples/qml/referenceexamples/signal/birthdayparty.h
index 6d7e022df0..c4a4da5dfb 100644
--- a/examples/qml/referenceexamples/signal/birthdayparty.h
+++ b/examples/qml/referenceexamples/signal/birthdayparty.h
@@ -61,7 +61,7 @@ class BirthdayPartyAttached : public QObject
     Q_PROPERTY(QDate rsvp READ rsvp WRITE setRsvp)
     QML_ANONYMOUS
 public:
-    BirthdayPartyAttached(QObject *object);
+    using QObject::QObject;
 
     QDate rsvp() const;
     void setRsvp(QDate);
@@ -79,14 +79,14 @@ class BirthdayParty : public QObject
     QML_ELEMENT
     QML_ATTACHED(BirthdayPartyAttached)
 public:
-    BirthdayParty(QObject *parent = nullptr);
+    using QObject::QObject;
 
     Person *host() const;
     void setHost(Person *);
 
     QQmlListProperty<Person> guests();
-    int guestCount() const;
-    Person *guest(int) const;
+    qsizetype guestCount() const;
+    Person *guest(qsizetype) const;
 
     static BirthdayPartyAttached *qmlAttachedProperties(QObject *);
 
@@ -97,7 +97,7 @@ signals:
 // ![0]
 
 private:
-    Person *m_host;
+    Person *m_host = nullptr;
     QList<Person *> m_guests;
 };
 
diff --git a/examples/qml/referenceexamples/signal/main.cpp b/examples/qml/referenceexamples/signal/main.cpp
index 7ef3595a8c..d0b060d8e6 100644
--- a/examples/qml/referenceexamples/signal/main.cpp
+++ b/examples/qml/referenceexamples/signal/main.cpp
@@ -63,14 +63,14 @@ int main(int argc, char ** argv)
     auto *party = qobject_cast<BirthdayParty *>(component.create());
 
     if (party && party->host()) {
-        qWarning() << party->host()->name() << "is having a birthday!";
+        qInfo() << party->host()->name() << "is having a birthday!";
 
         if (qobject_cast<Boy *>(party->host()))
-            qWarning() << "He is inviting:";
+            qInfo() << "He is inviting:";
         else
-            qWarning() << "She is inviting:";
+            qInfo() << "She is inviting:";
 
-        for (int ii = 0; ii < party->guestCount(); ++ii) {
+        for (qsizetype ii = 0; ii < party->guestCount(); ++ii) {
             Person *guest = party->guest(ii);
 
             QDate rsvpDate;
@@ -80,9 +80,9 @@ int main(int argc, char ** argv)
                 rsvpDate = attached->property("rsvp").toDate();
 
             if (rsvpDate.isNull())
-                qWarning() << "   " << guest->name() << "RSVP date: Hasn't RSVP'd";
+                qInfo() << "   " << guest->name() << "RSVP date: Hasn't RSVP'd";
             else
-                qWarning() << "   " << guest->name() << "RSVP date:" << qPrintable(rsvpDate.toString());
+                qInfo() << "   " << guest->name() << "RSVP date:" << rsvpDate.toString();
         }
 
         party->startParty();
diff --git a/examples/qml/referenceexamples/signal/person.cpp b/examples/qml/referenceexamples/signal/person.cpp
index 0603644108..4e52da76c8 100644
--- a/examples/qml/referenceexamples/signal/person.cpp
+++ b/examples/qml/referenceexamples/signal/person.cpp
@@ -1,6 +1,6 @@
 /****************************************************************************
 **
-** Copyright (C) 2017 The Qt Company Ltd.
+** Copyright (C) 2021 The Qt Company Ltd.
 ** Contact: https://www.qt.io/licensing/
 **
 ** This file is part of the examples of the Qt Toolkit.
@@ -47,12 +47,8 @@
 ** $QT_END_LICENSE$
 **
 ****************************************************************************/
-#include "person.h"
 
-ShoeDescription::ShoeDescription(QObject *parent)
-: QObject(parent), m_size(0), m_price(0)
-{
-}
+#include "person.h"
 
 int ShoeDescription::size() const
 {
@@ -94,11 +90,6 @@ void ShoeDescription::setPrice(qreal p)
     m_price = p;
 }
 
-Person::Person(QObject *parent)
-: QObject(parent)
-{
-}
-
 QString Person::name() const
 {
     return m_name;
@@ -113,16 +104,3 @@ ShoeDescription *Person::shoe()
 {
     return &m_shoe;
 }
-
-
-Boy::Boy(QObject * parent)
-: Person(parent)
-{
-}
-
-
-Girl::Girl(QObject * parent)
-: Person(parent)
-{
-}
-
diff --git a/examples/qml/referenceexamples/signal/person.h b/examples/qml/referenceexamples/signal/person.h
index 7283f39f61..ddd3baa5f2 100644
--- a/examples/qml/referenceexamples/signal/person.h
+++ b/examples/qml/referenceexamples/signal/person.h
@@ -1,6 +1,6 @@
 /****************************************************************************
 **
-** Copyright (C) 2017 The Qt Company Ltd.
+** Copyright (C) 2021 The Qt Company Ltd.
 ** Contact: https://www.qt.io/licensing/
 **
 ** This file is part of the examples of the Qt Toolkit.
@@ -47,6 +47,7 @@
 ** $QT_END_LICENSE$
 **
 ****************************************************************************/
+
 #ifndef PERSON_H
 #define PERSON_H
 
@@ -63,7 +64,7 @@ class ShoeDescription : public QObject
     Q_PROPERTY(qreal price READ price WRITE setPrice)
     QML_ANONYMOUS
 public:
-    ShoeDescription(QObject *parent = nullptr);
+    using QObject::QObject;
 
     int size() const;
     void setSize(int);
@@ -76,11 +77,12 @@ public:
 
     qreal price() const;
     void setPrice(qreal);
+
 private:
-    int m_size;
+    int m_size = 0;
     QColor m_color;
     QString m_brand;
-    qreal m_price;
+    qreal m_price = 0;
 };
 
 class Person : public QObject
@@ -90,7 +92,7 @@ class Person : public QObject
     Q_PROPERTY(ShoeDescription *shoe READ shoe)
     QML_ANONYMOUS
 public:
-    Person(QObject *parent = nullptr);
+    using QObject::QObject;
 
     QString name() const;
     void setName(const QString &);
@@ -106,7 +108,7 @@ class Boy : public Person
     Q_OBJECT
     QML_ELEMENT
 public:
-    Boy(QObject * parent = nullptr);
+    using Person::Person;
 };
 
 class Girl : public Person
@@ -114,7 +116,7 @@ class Girl : public Person
     Q_OBJECT
     QML_ELEMENT
 public:
-    Girl(QObject * parent = nullptr);
+    using Person::Person;
 };
 
 #endif // PERSON_H
diff --git a/examples/qml/referenceexamples/valuesource/birthdayparty.cpp b/examples/qml/referenceexamples/valuesource/birthdayparty.cpp
index 7ad11066cb..ced34c0cbb 100644
--- a/examples/qml/referenceexamples/valuesource/birthdayparty.cpp
+++ b/examples/qml/referenceexamples/valuesource/birthdayparty.cpp
@@ -1,6 +1,6 @@
 /****************************************************************************
 **
-** Copyright (C) 2017 The Qt Company Ltd.
+** Copyright (C) 2021 The Qt Company Ltd.
 ** Contact: https://www.qt.io/licensing/
 **
 ** This file is part of the examples of the Qt Toolkit.
@@ -47,12 +47,8 @@
 ** $QT_END_LICENSE$
 **
 ****************************************************************************/
-#include "birthdayparty.h"
 
-BirthdayPartyAttached::BirthdayPartyAttached(QObject *object)
-: QObject(object)
-{
-}
+#include "birthdayparty.h"
 
 QDate BirthdayPartyAttached::rsvp() const
 {
@@ -64,12 +60,6 @@ void BirthdayPartyAttached::setRsvp(QDate d)
     m_rsvp = d;
 }
 
-
-BirthdayParty::BirthdayParty(QObject *parent)
-: QObject(parent), m_host(nullptr)
-{
-}
-
 Person *BirthdayParty::host() const
 {
     return m_host;
@@ -85,12 +75,12 @@ QQmlListProperty<Person> BirthdayParty::guests()
     return {this, &m_guests};
 }
 
-int BirthdayParty::guestCount() const
+qsizetype BirthdayParty::guestCount() const
 {
     return m_guests.count();
 }
 
-Person *BirthdayParty::guest(int index) const
+Person *BirthdayParty::guest(qsizetype index) const
 {
     return m_guests.at(index);
 }
@@ -108,11 +98,10 @@ QString BirthdayParty::announcement() const
 
 void BirthdayParty::setAnnouncement(const QString &speak)
 {
-    qWarning() << qPrintable(speak);
+    qInfo().noquote() << speak;
 }
 
 BirthdayPartyAttached *BirthdayParty::qmlAttachedProperties(QObject *object)
 {
     return new BirthdayPartyAttached(object);
 }
-
diff --git a/examples/qml/referenceexamples/valuesource/birthdayparty.h b/examples/qml/referenceexamples/valuesource/birthdayparty.h
index abd6363571..4c661499ce 100644
--- a/examples/qml/referenceexamples/valuesource/birthdayparty.h
+++ b/examples/qml/referenceexamples/valuesource/birthdayparty.h
@@ -1,6 +1,6 @@
 /****************************************************************************
 **
-** Copyright (C) 2017 The Qt Company Ltd.
+** Copyright (C) 2021 The Qt Company Ltd.
 ** Contact: https://www.qt.io/licensing/
 **
 ** This file is part of the examples of the Qt Toolkit.
@@ -47,6 +47,7 @@
 ** $QT_END_LICENSE$
 **
 ****************************************************************************/
+
 #ifndef BIRTHDAYPARTY_H
 #define BIRTHDAYPARTY_H
 
@@ -62,7 +63,7 @@ class BirthdayPartyAttached : public QObject
     Q_PROPERTY(QDate rsvp READ rsvp WRITE setRsvp)
     QML_ANONYMOUS
 public:
-    BirthdayPartyAttached(QObject *object);
+    using QObject::QObject;
 
     QDate rsvp() const;
     void setRsvp(QDate);
@@ -83,14 +84,14 @@ class BirthdayParty : public QObject
     QML_ELEMENT
     QML_ATTACHED(BirthdayPartyAttached)
 public:
-    BirthdayParty(QObject *parent = nullptr);
+    using QObject::QObject;
 
     Person *host() const;
     void setHost(Person *);
 
     QQmlListProperty<Person> guests();
-    int guestCount() const;
-    Person *guest(int) const;
+    qsizetype guestCount() const;
+    Person *guest(qsizetype) const;
 
     QString announcement() const;
     void setAnnouncement(const QString &);
@@ -98,11 +99,12 @@ public:
     static BirthdayPartyAttached *qmlAttachedProperties(QObject *);
 
     void startParty();
+
 signals:
     void partyStarted(QTime time);
 
 private:
-    Person *m_host;
+    Person *m_host = nullptr;
     QList<Person *> m_guests;
 };
 
diff --git a/examples/qml/referenceexamples/valuesource/happybirthdaysong.cpp b/examples/qml/referenceexamples/valuesource/happybirthdaysong.cpp
index da09d3d7ba..635a50ef12 100644
--- a/examples/qml/referenceexamples/valuesource/happybirthdaysong.cpp
+++ b/examples/qml/referenceexamples/valuesource/happybirthdaysong.cpp
@@ -1,6 +1,6 @@
 /****************************************************************************
 **
-** Copyright (C) 2017 The Qt Company Ltd.
+** Copyright (C) 2021 The Qt Company Ltd.
 ** Contact: https://www.qt.io/licensing/
 **
 ** This file is part of the examples of the Qt Toolkit.
@@ -47,13 +47,13 @@
 ** $QT_END_LICENSE$
 **
 ****************************************************************************/
+
 #include "happybirthdaysong.h"
 #include <QTimer>
 
-HappyBirthdaySong::HappyBirthdaySong(QObject *parent)
-: QObject(parent), m_line(-1)
+HappyBirthdaySong::HappyBirthdaySong(QObject *parent) :
+      QObject(parent)
 {
-    setName(QString());
     auto *timer = new QTimer(this);
     QObject::connect(timer, &QTimer::timeout, this, &HappyBirthdaySong::advance);
     timer->start(1000);
diff --git a/examples/qml/referenceexamples/valuesource/happybirthdaysong.h b/examples/qml/referenceexamples/valuesource/happybirthdaysong.h
index 2600208968..146e336487 100644
--- a/examples/qml/referenceexamples/valuesource/happybirthdaysong.h
+++ b/examples/qml/referenceexamples/valuesource/happybirthdaysong.h
@@ -1,6 +1,6 @@
 /****************************************************************************
 **
-** Copyright (C) 2017 The Qt Company Ltd.
+** Copyright (C) 2021 The Qt Company Ltd.
 ** Contact: https://www.qt.io/licensing/
 **
 ** This file is part of the examples of the Qt Toolkit.
@@ -47,6 +47,7 @@
 ** $QT_END_LICENSE$
 **
 ****************************************************************************/
+
 #ifndef HAPPYBIRTHDAYSONG_H
 #define HAPPYBIRTHDAYSONG_H
 
@@ -66,7 +67,7 @@ class HappyBirthdaySong : public QObject, public QQmlPropertyValueSource
 // ![1]
     QML_ELEMENT
 public:
-    HappyBirthdaySong(QObject *parent = nullptr);
+    explicit HappyBirthdaySong(QObject *parent = nullptr);
 
     void setTarget(const QQmlProperty &) override;
 // ![1]
@@ -78,7 +79,7 @@ private slots:
     void advance();
 
 private:
-    int m_line;
+    qsizetype m_line = -1;
     QStringList m_lyrics;
     QQmlProperty m_target;
     QString m_name;
diff --git a/examples/qml/referenceexamples/valuesource/main.cpp b/examples/qml/referenceexamples/valuesource/main.cpp
index 2e9995fcd8..a100497659 100644
--- a/examples/qml/referenceexamples/valuesource/main.cpp
+++ b/examples/qml/referenceexamples/valuesource/main.cpp
@@ -64,14 +64,14 @@ int main(int argc, char ** argv)
     auto *party = qobject_cast<BirthdayParty *>(component.create());
 
     if (party && party->host()) {
-        qWarning() << party->host()->name() << "is having a birthday!";
+        qInfo() << party->host()->name() << "is having a birthday!";
 
         if (qobject_cast<Boy *>(party->host()))
-            qWarning() << "He is inviting:";
+            qInfo() << "He is inviting:";
         else
-            qWarning() << "She is inviting:";
+            qInfo() << "She is inviting:";
 
-        for (int ii = 0; ii < party->guestCount(); ++ii) {
+        for (qsizetype ii = 0; ii < party->guestCount(); ++ii) {
             Person *guest = party->guest(ii);
 
             QDate rsvpDate;
@@ -81,9 +81,9 @@ int main(int argc, char ** argv)
                 rsvpDate = attached->property("rsvp").toDate();
 
             if (rsvpDate.isNull())
-                qWarning() << "   " << guest->name() << "RSVP date: Hasn't RSVP'd";
+                qInfo() << "   " << guest->name() << "RSVP date: Hasn't RSVP'd";
             else
-                qWarning() << "   " << guest->name() << "RSVP date:" << qPrintable(rsvpDate.toString());
+                qInfo() << "   " << guest->name() << "RSVP date:" << rsvpDate.toString();
         }
 
         party->startParty();
diff --git a/examples/qml/referenceexamples/valuesource/person.cpp b/examples/qml/referenceexamples/valuesource/person.cpp
index 0603644108..4e52da76c8 100644
--- a/examples/qml/referenceexamples/valuesource/person.cpp
+++ b/examples/qml/referenceexamples/valuesource/person.cpp
@@ -1,6 +1,6 @@
 /****************************************************************************
 **
-** Copyright (C) 2017 The Qt Company Ltd.
+** Copyright (C) 2021 The Qt Company Ltd.
 ** Contact: https://www.qt.io/licensing/
 **
 ** This file is part of the examples of the Qt Toolkit.
@@ -47,12 +47,8 @@
 ** $QT_END_LICENSE$
 **
 ****************************************************************************/
-#include "person.h"
 
-ShoeDescription::ShoeDescription(QObject *parent)
-: QObject(parent), m_size(0), m_price(0)
-{
-}
+#include "person.h"
 
 int ShoeDescription::size() const
 {
@@ -94,11 +90,6 @@ void ShoeDescription::setPrice(qreal p)
     m_price = p;
 }
 
-Person::Person(QObject *parent)
-: QObject(parent)
-{
-}
-
 QString Person::name() const
 {
     return m_name;
@@ -113,16 +104,3 @@ ShoeDescription *Person::shoe()
 {
     return &m_shoe;
 }
-
-
-Boy::Boy(QObject * parent)
-: Person(parent)
-{
-}
-
-
-Girl::Girl(QObject * parent)
-: Person(parent)
-{
-}
-
diff --git a/examples/qml/referenceexamples/valuesource/person.h b/examples/qml/referenceexamples/valuesource/person.h
index 7283f39f61..ed77f8c4d8 100644
--- a/examples/qml/referenceexamples/valuesource/person.h
+++ b/examples/qml/referenceexamples/valuesource/person.h
@@ -1,6 +1,6 @@
 /****************************************************************************
 **
-** Copyright (C) 2017 The Qt Company Ltd.
+** Copyright (C) 2021 The Qt Company Ltd.
 ** Contact: https://www.qt.io/licensing/
 **
 ** This file is part of the examples of the Qt Toolkit.
@@ -47,6 +47,7 @@
 ** $QT_END_LICENSE$
 **
 ****************************************************************************/
+
 #ifndef PERSON_H
 #define PERSON_H
 
@@ -63,7 +64,7 @@ class ShoeDescription : public QObject
     Q_PROPERTY(qreal price READ price WRITE setPrice)
     QML_ANONYMOUS
 public:
-    ShoeDescription(QObject *parent = nullptr);
+    using QObject::QObject;
 
     int size() const;
     void setSize(int);
@@ -76,21 +77,24 @@ public:
 
     qreal price() const;
     void setPrice(qreal);
+
 private:
-    int m_size;
+    int m_size = 0;
     QColor m_color;
     QString m_brand;
-    qreal m_price;
+    qreal m_price = 0;
 };
 
 class Person : public QObject
 {
     Q_OBJECT
     Q_PROPERTY(QString name READ name WRITE setName)
+// ![1]
     Q_PROPERTY(ShoeDescription *shoe READ shoe)
+// ![1]
     QML_ANONYMOUS
 public:
-    Person(QObject *parent = nullptr);
+    using QObject::QObject;
 
     QString name() const;
     void setName(const QString &);
@@ -106,7 +110,7 @@ class Boy : public Person
     Q_OBJECT
     QML_ELEMENT
 public:
-    Boy(QObject * parent = nullptr);
+    using Person::Person;
 };
 
 class Girl : public Person
@@ -114,7 +118,7 @@ class Girl : public Person
     Q_OBJECT
     QML_ELEMENT
 public:
-    Girl(QObject * parent = nullptr);
+    using Person::Person;
 };
 
 #endif // PERSON_H