Revamp SQL examples to C++11

Changed signals and slots to new syntax, used nullptr and replaced
foreach with new C++11 range based for loops.
Also fixed a few minor flaws.

Task-number: QTBUG-60633
Change-Id: Ice4030133971912f96752d9d84c638c70fd73e35
Reviewed-by: Jesus Fernandez <Jesus.Fernandez@qt.io>
Reviewed-by: André Hartmann <aha_1980@gmx.de>
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@qt.io>

30 files changed, 171 insertions, 146 deletions

diff --git a/examples/sql/cachedtable/tableeditor.cpp b/examples/sql/cachedtable/tableeditor.cpp
index 71e441486d..95c3047c76 100644
--- a/examples/sql/cachedtable/tableeditor.cpp
+++ b/examples/sql/cachedtable/tableeditor.cpp
@@ -85,9 +85,9 @@ TableEditor::TableEditor(const QString &tableName, QWidget *parent)
 //! [2]
 
 //! [3]
-    connect(submitButton, SIGNAL(clicked()), this, SLOT(submit()));
-    connect(revertButton, SIGNAL(clicked()), model, SLOT(revertAll()));
-    connect(quitButton, SIGNAL(clicked()), this, SLOT(close()));
+    connect(submitButton, &QPushButton::clicked, this, &TableEditor::submit);
+    connect(revertButton, &QPushButton::clicked,  model, &QSqlTableModel::revertAll);
+    connect(quitButton, &QPushButton::clicked, this, &TableEditor::close);
 //! [3]
 
 //! [4]
diff --git a/examples/sql/cachedtable/tableeditor.h b/examples/sql/cachedtable/tableeditor.h
index 6544276cbe..727aa88ab3 100644
--- a/examples/sql/cachedtable/tableeditor.h
+++ b/examples/sql/cachedtable/tableeditor.h
@@ -65,7 +65,7 @@ class TableEditor : public QWidget
     Q_OBJECT
 
 public:
-    explicit TableEditor(const QString &tableName, QWidget *parent = 0);
+    explicit TableEditor(const QString &tableName, QWidget *parent = nullptr);
 
 private slots:
     void submit();
diff --git a/examples/sql/connection.h b/examples/sql/connection.h
index 3bedf4b061..482feff5b4 100644
--- a/examples/sql/connection.h
+++ b/examples/sql/connection.h
@@ -70,12 +70,12 @@ static bool createConnection()
     QSqlDatabase db = QSqlDatabase::addDatabase("QSQLITE");
     db.setDatabaseName(":memory:");
     if (!db.open()) {
-        QMessageBox::critical(0, qApp->tr("Cannot open database"),
-            qApp->tr("Unable to establish a database connection.\n"
-                     "This example needs SQLite support. Please read "
-                     "the Qt SQL driver documentation for information how "
-                     "to build it.\n\n"
-                     "Click Cancel to exit."), QMessageBox::Cancel);
+        QMessageBox::critical(nullptr, QObject::tr("Cannot open database"),
+            QObject::tr("Unable to establish a database connection.\n"
+                        "This example needs SQLite support. Please read "
+                        "the Qt SQL driver documentation for information how "
+                        "to build it.\n\n"
+                        "Click Cancel to exit."), QMessageBox::Cancel);
         return false;
     }
 
diff --git a/examples/sql/doc/src/drilldown.qdoc b/examples/sql/doc/src/drilldown.qdoc
index 1fcac41eeb..e8841d2013 100644
--- a/examples/sql/doc/src/drilldown.qdoc
+++ b/examples/sql/doc/src/drilldown.qdoc
@@ -172,11 +172,20 @@
     \snippet drilldown/informationwindow.cpp 4
 
     Finally, we connect the "something's changed" signals in the
-    editors to our custom \c enableButtons() slot, enabling the users
-    to either submit or revert their changes. We add all the widgets
-    into a layout, store the item ID and the name of the displayed
-    image file for future reference, and set the window title and
-    initial size.
+    editors to our custom \c enableButtons slot, enabling the users
+    to either submit or revert their changes.
+    We need to use lambdas for connecting the \c enableButtons slot
+    because its signature does not match \c QTextEdit::textChanged
+    and \c QComboBox::currentIndexChanged.
+    Since the latter has another overload with the signature
+    \c {const QString &} and the selected signal would be ambiguous,
+    we need to use \c QOverload<int>::of to select a specific overload
+    for \c currentIndexChanged.
+
+    We add all the widgets into a layout, store the item ID and the
+    name of the displayed image file for future reference, and set
+    the window title and initial size.
+
 
     Note that we also set the Qt::Window window flag to indicate that
     our widget is in fact a window, with a window system frame and a
@@ -389,19 +398,21 @@
     \snippet drilldown/view.cpp 6
 
     The \c showInformation() function is given an \c ImageItem object
-    as argument, and starts off by extracting the item's item
-    ID. Then it determines if there already is created an information
-    window for this location. If it is, and the window is visible, it
-    ensures that the window is raised to the top of the widget stack
-    and activated. If the window exists but is hidden, calling its \l
-    {QWidget::}{show()} slot gives the same result.
+    as argument, and starts off by extracting the item's item ID.
 
+    Then it determines if there already is created an information
+    window for this location.
     If no window for the given location exists, we create one by
     passing the item ID, a pointer to the model, and our view as a
     parent, to the \c InformationWindow constructor. Note that we
     connect the information window's \c imageChanged() signal to \e
     this widget's \c updateImage() slot, before we give it a suitable
     position and add it to the list of existing windows.
+    If there is a window for the given location, and that window is
+    visible, it ensures that the window is raised to the top of the
+    widget stack and activated. If it is hidden, calling its \l
+    {QWidget::}{show()} slot gives the same result.
+
 
     \snippet drilldown/view.cpp 7
 
diff --git a/examples/sql/drilldown/imageitem.cpp b/examples/sql/drilldown/imageitem.cpp
index 4e440fc786..04ec614755 100644
--- a/examples/sql/drilldown/imageitem.cpp
+++ b/examples/sql/drilldown/imageitem.cpp
@@ -60,8 +60,8 @@ ImageItem::ImageItem(int id, const QPixmap &pixmap, QGraphicsItem *parent)
     timeLine.setDuration(150);
     timeLine.setFrameRange(0, 150);
 
-    connect(&timeLine, SIGNAL(frameChanged(int)), this, SLOT(setFrame(int)));
-    connect(&timeLine, SIGNAL(finished()), this, SLOT(updateItemPosition()));
+    connect(&timeLine, &QTimeLine::frameChanged, this, &ImageItem::setFrame);
+    connect(&timeLine, &QTimeLine::finished, this, &ImageItem::updateItemPosition);
 
     adjust();
 }
@@ -116,7 +116,7 @@ void ImageItem::adjust()
 //! [4]
 
 //! [5]
-int ImageItem::id()
+int ImageItem::id() const
 {
     return recordId;
 }
diff --git a/examples/sql/drilldown/imageitem.h b/examples/sql/drilldown/imageitem.h
index 4f773a6dfc..abb9103c7e 100644
--- a/examples/sql/drilldown/imageitem.h
+++ b/examples/sql/drilldown/imageitem.h
@@ -60,10 +60,10 @@ class ImageItem : public QObject, public QGraphicsPixmapItem
     Q_OBJECT
 
 public:
-    ImageItem(int id, const QPixmap &pixmap, QGraphicsItem *parent = 0);
+    ImageItem(int id, const QPixmap &pixmap, QGraphicsItem *parent = nullptr);
 
     void adjust();
-    int id();
+    int id() const;
 
 protected:
     void hoverEnterEvent(QGraphicsSceneHoverEvent *event) override;
diff --git a/examples/sql/drilldown/informationwindow.cpp b/examples/sql/drilldown/informationwindow.cpp
index 2536b0ca91..0007432672 100644
--- a/examples/sql/drilldown/informationwindow.cpp
+++ b/examples/sql/drilldown/informationwindow.cpp
@@ -84,10 +84,12 @@ InformationWindow::InformationWindow(int id, QSqlRelationalTableModel *items,
 //! [3]
 
 //! [4]
-    connect(descriptionEditor, SIGNAL(textChanged()),
-            this, SLOT(enableButtons()));
-    connect(imageFileEditor, SIGNAL(currentIndexChanged(int)),
-            this, SLOT(enableButtons()));
+    connect(descriptionEditor, &QTextEdit::textChanged, [=]() {
+        enableButtons();
+    });
+    connect(imageFileEditor, QOverload<int>::of(&QComboBox::currentIndexChanged), [=]() {
+        enableButtons();
+    });
 
     QFormLayout *formLayout = new QFormLayout;
     formLayout->addRow(itemLabel, itemText);
@@ -109,7 +111,7 @@ InformationWindow::InformationWindow(int id, QSqlRelationalTableModel *items,
 //! [4]
 
 //! [5]
-int InformationWindow::id()
+int InformationWindow::id() const
 {
     return itemId;
 }
@@ -149,9 +151,9 @@ void InformationWindow::createButtons()
 
     closeButton->setDefault(true);
 
-    connect(closeButton, SIGNAL(clicked()), this, SLOT(close()));
-    connect(revertButton, SIGNAL(clicked()), this, SLOT(revert()));
-    connect(submitButton, SIGNAL(clicked()), this, SLOT(submit()));
+    connect(closeButton, &QPushButton::clicked, this, &InformationWindow::close);
+    connect(revertButton, &QPushButton::clicked, this, &InformationWindow::revert);
+    connect(submitButton, &QPushButton::clicked, this, &InformationWindow::submit);
 //! [8]
 
 //! [9]
diff --git a/examples/sql/drilldown/informationwindow.h b/examples/sql/drilldown/informationwindow.h
index 6e87cea65a..653837d722 100644
--- a/examples/sql/drilldown/informationwindow.h
+++ b/examples/sql/drilldown/informationwindow.h
@@ -61,9 +61,9 @@ class InformationWindow : public QDialog
 
 public:
     InformationWindow(int id, QSqlRelationalTableModel *items,
-                      QWidget *parent = 0);
+                      QWidget *parent = nullptr);
 
-    int id();
+    int id() const;
 
 signals:
     void imageChanged(int id, const QString &fileName);
@@ -83,16 +83,16 @@ private:
     int itemId;
     QString displayedImage;
 
-    QComboBox *imageFileEditor;
-    QLabel *itemText;
-    QTextEdit *descriptionEditor;
+    QComboBox *imageFileEditor = nullptr;
+    QLabel *itemText = nullptr;
+    QTextEdit *descriptionEditor = nullptr;
 
-    QPushButton *closeButton;
-    QPushButton *submitButton;
-    QPushButton *revertButton;
-    QDialogButtonBox *buttonBox;
+    QPushButton *closeButton = nullptr;
+    QPushButton *submitButton = nullptr;
+    QPushButton *revertButton = nullptr;
+    QDialogButtonBox *buttonBox = nullptr;
 
-    QDataWidgetMapper *mapper;
+    QDataWidgetMapper *mapper = nullptr;
 };
 //! [2]
 
diff --git a/examples/sql/drilldown/main.cpp b/examples/sql/drilldown/main.cpp
index 3465d11b4d..db3320de48 100644
--- a/examples/sql/drilldown/main.cpp
+++ b/examples/sql/drilldown/main.cpp
@@ -48,10 +48,13 @@
 **
 ****************************************************************************/
 
-#include <QtWidgets>
-
-#include "../connection.h"
 #include "view.h"
+#include "../connection.h"
+
+#include <QApplication>
+
+#include <stdlib.h>
+
 
 int main(int argc, char *argv[])
 {
@@ -60,7 +63,7 @@ int main(int argc, char *argv[])
     QApplication app(argc, argv);
 
     if (!createConnection())
-        return 1;
+        return EXIT_FAILURE;
 
     View view("items", "images");
     view.show();
diff --git a/examples/sql/drilldown/view.cpp b/examples/sql/drilldown/view.cpp
index fc05d2fcaf..13e9310061 100644
--- a/examples/sql/drilldown/view.cpp
+++ b/examples/sql/drilldown/view.cpp
@@ -89,8 +89,6 @@ void View::addItems()
     int topMargin = 40;
 
     for (int i = 0; i < itemCount; i++) {
-        ImageItem *image;
-        QGraphicsTextItem *label;
         QSqlRecord record = itemTable->record(i);
 
         int id = record.value("id").toInt();
@@ -101,12 +99,12 @@ void View::addItems()
         int x = ((i % 2) * imageOffset) + leftMargin + columnOffset;
         int y = ((i / 2) * imageOffset) + topMargin;
 
-        image = new ImageItem(id, QPixmap(":/" + file));
+        ImageItem *image = new ImageItem(id, QPixmap(":/" + file));
         image->setData(0, i);
         image->setPos(x, y);
         scene->addItem(image);
 
-        label = scene->addText(item);
+        QGraphicsTextItem *label = scene->addText(item);
         label->setDefaultTextColor(QColor("#d7d6d5"));
         QPointF labelOffset((120 - label->boundingRect().width()) / 2, 120.0);
         label->setPos(QPointF(x, y) + labelOffset);
@@ -133,22 +131,22 @@ void View::showInformation(ImageItem *image)
         return;
 
     InformationWindow *window = findWindow(id);
-    if (window && window->isVisible()) {
-        window->raise();
-        window->activateWindow();
-    } else if (window && !window->isVisible()) {
-        window->show();
-    } else {
-        InformationWindow *window;
+    if (!window) {
         window = new InformationWindow(id, itemTable, this);
 
-        connect(window, SIGNAL(imageChanged(int,QString)),
-                this, SLOT(updateImage(int,QString)));
+        connect(window, QOverload<int,const QString &>::of(&InformationWindow::imageChanged),
+                this, QOverload<int,const QString &>::of(&View::updateImage));
 
         window->move(pos() + QPoint(20, 40));
         window->show();
         informationWindows.append(window);
     }
+
+    if (window->isVisible()) {
+        window->raise();
+        window->activateWindow();
+    } else
+        window->show();
 }
 //! [6]
 
@@ -172,19 +170,13 @@ void View::updateImage(int id, const QString &fileName)
 //! [7]
 
 //! [8]
-InformationWindow* View::findWindow(int id)
+InformationWindow *View::findWindow(int id) const
 {
-    QList<InformationWindow*>::iterator i, beginning, end;
-
-    beginning = informationWindows.begin();
-    end = informationWindows.end();
-
-    for (i = beginning; i != end; ++i) {
-        InformationWindow *window = (*i);
+    for (auto window : informationWindows) {
         if (window && (window->id() == id))
             return window;
     }
-    return 0;
+    return nullptr;
 }
 //! [8]
 
diff --git a/examples/sql/drilldown/view.h b/examples/sql/drilldown/view.h
index 9d6ef0e853..5afa1a25e9 100644
--- a/examples/sql/drilldown/view.h
+++ b/examples/sql/drilldown/view.h
@@ -63,7 +63,7 @@ class View : public QGraphicsView
     Q_OBJECT
 
 public:
-    View(const QString &items, const QString &images, QWidget *parent = 0);
+    View(const QString &items, const QString &images, QWidget *parent = nullptr);
 
 protected:
     void mouseReleaseEvent(QMouseEvent *event) override;
@@ -77,7 +77,7 @@ private slots:
 //! [2]
 private:
     void addItems();
-    InformationWindow* findWindow(int id);
+    InformationWindow *findWindow(int id) const;
     void showInformation(ImageItem *image);
 
     QGraphicsScene *scene;
diff --git a/examples/sql/masterdetail/database.h b/examples/sql/masterdetail/database.h
index 3139deb0b2..9cbca6f749 100644
--- a/examples/sql/masterdetail/database.h
+++ b/examples/sql/masterdetail/database.h
@@ -61,12 +61,12 @@ static bool createConnection()
     QSqlDatabase db = QSqlDatabase::addDatabase("QSQLITE");
     db.setDatabaseName(":memory:");
     if (!db.open()) {
-        QMessageBox::critical(0, qApp->tr("Cannot open database"),
-            qApp->tr("Unable to establish a database connection.\n"
-                     "This example needs SQLite support. Please read "
-                     "the Qt SQL driver documentation for information how "
-                     "to build it.\n\n"
-                     "Click Cancel to exit."), QMessageBox::Cancel);
+        QMessageBox::critical(nullptr, QObject::tr("Cannot open database"),
+            QObject::tr("Unable to establish a database connection.\n"
+                        "This example needs SQLite support. Please read "
+                        "the Qt SQL driver documentation for information how "
+                        "to build it.\n\n"
+                        "Click Cancel to exit."), QMessageBox::Cancel);
         return false;
     }
 
diff --git a/examples/sql/masterdetail/dialog.cpp b/examples/sql/masterdetail/dialog.cpp
index 5bb213230e..bb1812eace 100644
--- a/examples/sql/masterdetail/dialog.cpp
+++ b/examples/sql/masterdetail/dialog.cpp
@@ -155,12 +155,12 @@ int Dialog::addNewAlbum(const QString &title, int artistId)
     return id;
 }
 
-void Dialog::addTracks(int albumId, QStringList tracks)
+void Dialog::addTracks(int albumId, const QStringList &tracks)
 {
     QDomElement albumNode = albumDetails.createElement("album");
     albumNode.setAttribute("id", albumId);
 
-    for (int i = 0; i < tracks.count(); i++) {
+    for (int i = 0; i < tracks.count(); ++i) {
         QString trackNumber = QString::number(i);
         if (i < 10)
             trackNumber.prepend('0');
@@ -254,9 +254,9 @@ QDialogButtonBox *Dialog::createButtons()
 
     closeButton->setDefault(true);
 
-    connect(closeButton, SIGNAL(clicked()), this, SLOT(close()));
-    connect(revertButton, SIGNAL(clicked()), this, SLOT(revert()));
-    connect(submitButton, SIGNAL(clicked()), this, SLOT(submit()));
+    connect(closeButton, &QPushButton::clicked, this, &Dialog::close);
+    connect(revertButton, &QPushButton::clicked,  this, &Dialog::revert);
+    connect(submitButton, &QPushButton::clicked, this, &Dialog::submit);
 
     QDialogButtonBox *buttonBox = new QDialogButtonBox;
     buttonBox->addButton(submitButton, QDialogButtonBox::ResetRole);
@@ -270,7 +270,7 @@ QModelIndex Dialog::indexOfArtist(const QString &artist)
 {
     QSqlTableModel *artistModel = model->relationModel(2);
 
-    for (int i = 0; i < artistModel->rowCount(); i++) {
+    for (int i = 0; i < artistModel->rowCount(); ++i) {
         QSqlRecord record =  artistModel->record(i);
         if (record.value("artist") == artist)
             return artistModel->index(i, 1);
diff --git a/examples/sql/masterdetail/dialog.h b/examples/sql/masterdetail/dialog.h
index 1789207d8d..31c4d8552c 100644
--- a/examples/sql/masterdetail/dialog.h
+++ b/examples/sql/masterdetail/dialog.h
@@ -61,7 +61,7 @@ class Dialog : public QDialog
 
 public:
     Dialog(QSqlRelationalTableModel *albums, QDomDocument details,
-           QFile *output, QWidget *parent = 0);
+           QFile *output, QWidget *parent = nullptr);
 
 private slots:
     void revert();
@@ -70,12 +70,12 @@ private slots:
 private:
     int addNewAlbum(const QString &title, int artistId);
     int addNewArtist(const QString &name);
-    void addTracks(int albumId, QStringList tracks);
+    void addTracks(int albumId, const QStringList &tracks);
     QDialogButtonBox *createButtons();
     QGroupBox *createInputWidgets();
     int findArtistId(const QString &artist);
-    int generateAlbumId();
-    int generateArtistId();
+    static int generateAlbumId();
+    static int generateArtistId();
     void increaseAlbumCount(QModelIndex artistIndex);
     QModelIndex indexOfArtist(const QString &artist);
 
diff --git a/examples/sql/masterdetail/main.cpp b/examples/sql/masterdetail/main.cpp
index cc1a1c4a21..9a4172e55f 100644
--- a/examples/sql/masterdetail/main.cpp
+++ b/examples/sql/masterdetail/main.cpp
@@ -48,11 +48,14 @@
 **
 ****************************************************************************/
 
-#include <QtWidgets>
-
 #include "database.h"
 #include "mainwindow.h"
 
+#include <QApplication>
+#include <QFile>
+
+#include <stdlib.h>
+
 int main(int argc, char *argv[])
 {
     Q_INIT_RESOURCE(masterdetail);
@@ -60,10 +63,10 @@ int main(int argc, char *argv[])
     QApplication app(argc, argv);
 
     if (!createConnection())
-        return 1;
+        return EXIT_FAILURE;
 
-    QFile *albumDetails = new QFile("albumdetails.xml");
-    MainWindow window("artists", "albums", albumDetails);
+    QFile albumDetails("albumdetails.xml");
+    MainWindow window("artists", "albums", &albumDetails);
     window.show();
     return app.exec();
 }
diff --git a/examples/sql/masterdetail/mainwindow.cpp b/examples/sql/masterdetail/mainwindow.cpp
index 9fbc4c43a4..7f3479619a 100644
--- a/examples/sql/masterdetail/mainwindow.cpp
+++ b/examples/sql/masterdetail/mainwindow.cpp
@@ -78,10 +78,10 @@ MainWindow::MainWindow(const QString &artistTable, const QString &albumTable,
     uniqueAlbumId = model->rowCount();
     uniqueArtistId = artistView->count();
 
-    connect(model, SIGNAL(rowsInserted(QModelIndex,int,int)),
-            this, SLOT(updateHeader(QModelIndex,int,int)));
-    connect(model, SIGNAL(rowsRemoved(QModelIndex,int,int)),
-            this, SLOT(updateHeader(QModelIndex,int,int)));
+    connect(model, &QSqlRelationalTableModel::rowsInserted,
+            this, &MainWindow::updateHeader);
+    connect(model, &QSqlRelationalTableModel::rowsRemoved,
+            this, &MainWindow::updateHeader);
 
     QGridLayout *layout = new QGridLayout;
     layout->addWidget(artists, 0, 0);
@@ -145,7 +145,7 @@ void MainWindow::showAlbumDetails(QModelIndex index)
     titleLabel->show();
 
     QDomNodeList albums = albumData.elementsByTagName("album");
-    for (int i = 0; i < albums.count(); i++) {
+    for (int i = 0; i < albums.count(); ++i) {
         QDomNode album = albums.item(i);
         if (album.toElement().attribute("id") == albumId) {
             getTrackList(album.toElement());
@@ -164,9 +164,9 @@ void MainWindow::getTrackList(QDomNode album)
     QDomNode track;
     QString trackNumber;
 
-    for (int j = 0; j < tracks.count(); j++) {
+    for (int i = 0; i < tracks.count(); ++i) {
 
-        track = tracks.item(j);
+        track = tracks.item(i);
         trackNumber = track.toElement().attribute("number");
 
         QListWidgetItem *item = new QListWidgetItem(trackList);
@@ -222,7 +222,7 @@ void MainWindow::removeAlbumFromFile(int id)
 
     QDomNodeList albums = albumData.elementsByTagName("album");
 
-    for (int i = 0; i < albums.count(); i++) {
+    for (int i = 0; i < albums.count(); ++i) {
         QDomNode node = albums.item(i);
         if (node.toElement().attribute("id").toInt() == id) {
             albumData.elementsByTagName("archive").item(0).removeChild(node);
@@ -283,8 +283,8 @@ QGroupBox* MainWindow::createArtistGroupBox()
     artistView->setModel(model->relationModel(2));
     artistView->setModelColumn(1);
 
-    connect(artistView, SIGNAL(currentIndexChanged(int)),
-            this, SLOT(changeArtist(int)));
+    connect(artistView, QOverload<int>::of(&QComboBox::currentIndexChanged),
+            this, &MainWindow::changeArtist);
 
     QGroupBox *box = new QGroupBox(tr("Artist"));
 
@@ -314,10 +314,10 @@ QGroupBox* MainWindow::createAlbumGroupBox()
     locale.setNumberOptions(QLocale::OmitGroupSeparator);
     albumView->setLocale(locale);
 
-    connect(albumView, SIGNAL(clicked(QModelIndex)),
-            this, SLOT(showAlbumDetails(QModelIndex)));
-    connect(albumView, SIGNAL(activated(QModelIndex)),
-            this, SLOT(showAlbumDetails(QModelIndex)));
+    connect(albumView, &QTableView::clicked,
+            this, &MainWindow::showAlbumDetails);
+    connect(albumView, &QTableView::activated,
+            this, &MainWindow::showAlbumDetails);
 
     QVBoxLayout *layout = new QVBoxLayout;
     layout->addWidget(albumView, 0, 0);
@@ -383,11 +383,16 @@ void MainWindow::createMenuBar()
     helpMenu->addAction(aboutAction);
     helpMenu->addAction(aboutQtAction);
 
-    connect(addAction, SIGNAL(triggered(bool)), this, SLOT(addAlbum()));
-    connect(deleteAction, SIGNAL(triggered(bool)), this, SLOT(deleteAlbum()));
-    connect(quitAction, SIGNAL(triggered(bool)), this, SLOT(close()));
-    connect(aboutAction, SIGNAL(triggered(bool)), this, SLOT(about()));
-    connect(aboutQtAction, SIGNAL(triggered(bool)), qApp, SLOT(aboutQt()));
+    connect(addAction, &QAction::triggered,
+            this, &MainWindow::addAlbum);
+    connect(deleteAction, &QAction::triggered,
+            this, &MainWindow::deleteAlbum);
+    connect(quitAction, &QAction::triggered,
+            this, &MainWindow::close);
+    connect(aboutAction, &QAction::triggered,
+            this, &MainWindow::about);
+    connect(aboutQtAction, &QAction::triggered,
+            qApp, &QApplication::aboutQt);
 }
 
 void MainWindow::showImageLabel()
diff --git a/examples/sql/masterdetail/mainwindow.h b/examples/sql/masterdetail/mainwindow.h
index be3c6c94f4..dc6d8d1613 100644
--- a/examples/sql/masterdetail/mainwindow.h
+++ b/examples/sql/masterdetail/mainwindow.h
@@ -71,7 +71,7 @@ class MainWindow : public QMainWindow
 
 public:
     MainWindow(const QString &artistTable, const QString &albumTable,
-               QFile *albumDetails, QWidget *parent = 0);
+               QFile *albumDetails, QWidget *parent = nullptr);
 
 private slots:
     void about();
diff --git a/examples/sql/querymodel/customsqlmodel.h b/examples/sql/querymodel/customsqlmodel.h
index 5d2f625665..462d2ab822 100644
--- a/examples/sql/querymodel/customsqlmodel.h
+++ b/examples/sql/querymodel/customsqlmodel.h
@@ -59,7 +59,7 @@ class CustomSqlModel : public QSqlQueryModel
     Q_OBJECT
 
 public:
-    CustomSqlModel(QObject *parent = 0);
+    CustomSqlModel(QObject *parent = nullptr);
 
     QVariant data(const QModelIndex &item, int role) const override;
 };
diff --git a/examples/sql/querymodel/editablesqlmodel.h b/examples/sql/querymodel/editablesqlmodel.h
index 1341dd372a..e8caad2765 100644
--- a/examples/sql/querymodel/editablesqlmodel.h
+++ b/examples/sql/querymodel/editablesqlmodel.h
@@ -58,7 +58,7 @@ class EditableSqlModel : public QSqlQueryModel
     Q_OBJECT
 
 public:
-    EditableSqlModel(QObject *parent = 0);
+    EditableSqlModel(QObject *parent = nullptr);
 
     Qt::ItemFlags flags(const QModelIndex &index) const override;
     bool setData(const QModelIndex &index, const QVariant &value, int role) override;
diff --git a/examples/sql/querymodel/main.cpp b/examples/sql/querymodel/main.cpp
index 83804682f9..da19939dd8 100644
--- a/examples/sql/querymodel/main.cpp
+++ b/examples/sql/querymodel/main.cpp
@@ -48,12 +48,15 @@
 **
 ****************************************************************************/
 
-#include <QtWidgets>
-
 #include "../connection.h"
 #include "customsqlmodel.h"
 #include "editablesqlmodel.h"
 
+#include <QApplication>
+#include <QTableView>
+
+#include <stdlib.h>
+
 void initializeModel(QSqlQueryModel *model)
 {
     model->setQuery("select * from person");
@@ -80,7 +83,7 @@ int main(int argc, char *argv[])
 {
     QApplication app(argc, argv);
     if (!createConnection())
-        return 1;
+        return EXIT_FAILURE;
 
     QSqlQueryModel plainModel;
     EditableSqlModel editableModel;
diff --git a/examples/sql/relationaltablemodel/relationaltablemodel.cpp b/examples/sql/relationaltablemodel/relationaltablemodel.cpp
index 5292256cd9..c3c7d48d70 100644
--- a/examples/sql/relationaltablemodel/relationaltablemodel.cpp
+++ b/examples/sql/relationaltablemodel/relationaltablemodel.cpp
@@ -110,7 +110,8 @@ int main(int argc, char *argv[])
 {
     QApplication app(argc, argv);
     if (!createConnection())
-        return 1;
+        return EXIT_FAILURE;
+
     createRelationalTables();
 
     QSqlRelationalTableModel model;
diff --git a/examples/sql/sqlbrowser/browser.cpp b/examples/sql/sqlbrowser/browser.cpp
index d86c54404d..b05cf52099 100644
--- a/examples/sql/sqlbrowser/browser.cpp
+++ b/examples/sql/sqlbrowser/browser.cpp
@@ -165,11 +165,12 @@ void Browser::showTable(const QString &t)
     model->select();
     if (model->lastError().type() != QSqlError::NoError)
         emit statusMessage(model->lastError().text());
+
     table->setModel(model);
     table->setEditTriggers(QAbstractItemView::DoubleClicked|QAbstractItemView::EditKeyPressed);
+    connect(table->selectionModel(), &QItemSelectionModel::currentRowChanged,
+            this, &Browser::currentChanged);
 
-    connect(table->selectionModel(), SIGNAL(currentRowChanged(QModelIndex,QModelIndex)),
-            this, SLOT(currentChanged()));
     updateActions();
 }
 
@@ -189,7 +190,6 @@ void Browser::showMetaData(const QString &t)
     model->setHeaderData(5, Qt::Horizontal, "AutoValue");
     model->setHeaderData(6, Qt::Horizontal, "DefaultValue");
 
-
     for (int i = 0; i < rec.count(); ++i) {
         QSqlField fld = rec.field(i);
         model->setData(model->index(i, 0), fld.name());
diff --git a/examples/sql/sqlbrowser/browser.h b/examples/sql/sqlbrowser/browser.h
index fef410778b..3f98f487c3 100644
--- a/examples/sql/sqlbrowser/browser.h
+++ b/examples/sql/sqlbrowser/browser.h
@@ -65,7 +65,7 @@ class Browser: public QWidget, private Ui::Browser
 {
     Q_OBJECT
 public:
-    Browser(QWidget *parent = 0);
+    Browser(QWidget *parent = nullptr);
     virtual ~Browser();
 
     QSqlError addConnection(const QString &driver, const QString &dbName, const QString &host,
@@ -116,7 +116,9 @@ class CustomModel: public QSqlTableModel
 {
     Q_OBJECT
 public:
-    explicit CustomModel(QObject *parent = 0, QSqlDatabase db = QSqlDatabase()):QSqlTableModel(parent, db) {}
+    explicit CustomModel(QObject *parent = nullptr, QSqlDatabase db = QSqlDatabase())
+        : QSqlTableModel(parent, db) {}
+
     QVariant data(const QModelIndex &idx, int role) const override
     {
         if (role == Qt::BackgroundRole && isDirty(idx))
diff --git a/examples/sql/sqlbrowser/connectionwidget.cpp b/examples/sql/sqlbrowser/connectionwidget.cpp
index 888579c9af..658cfb77dc 100644
--- a/examples/sql/sqlbrowser/connectionwidget.cpp
+++ b/examples/sql/sqlbrowser/connectionwidget.cpp
@@ -63,8 +63,8 @@ ConnectionWidget::ConnectionWidget(QWidget *parent)
     tree->header()->setSectionResizeMode(QHeaderView::Stretch);
     QAction *refreshAction = new QAction(tr("Refresh"), tree);
     metaDataAction = new QAction(tr("Show Schema"), tree);
-    connect(refreshAction, SIGNAL(triggered()), SLOT(refresh()));
-    connect(metaDataAction, SIGNAL(triggered()), SLOT(showMetaData()));
+    connect(refreshAction, &QAction::triggered, this, &ConnectionWidget::refresh);
+    connect(metaDataAction, &QAction::triggered, this, &ConnectionWidget::showMetaData);
     tree->addAction(refreshAction);
     tree->addAction(metaDataAction);
     tree->setContextMenuPolicy(Qt::ActionsContextMenu);
@@ -146,7 +146,6 @@ void ConnectionWidget::setActive(QTreeWidgetItem *item)
 
 void ConnectionWidget::on_tree_itemActivated(QTreeWidgetItem *item, int /* column */)
 {
-
     if (!item)
         return;
 
diff --git a/examples/sql/sqlbrowser/connectionwidget.h b/examples/sql/sqlbrowser/connectionwidget.h
index 8b8e3a9a62..a805765f69 100644
--- a/examples/sql/sqlbrowser/connectionwidget.h
+++ b/examples/sql/sqlbrowser/connectionwidget.h
@@ -62,7 +62,7 @@ class ConnectionWidget: public QWidget
 {
     Q_OBJECT
 public:
-    ConnectionWidget(QWidget *parent = 0);
+    ConnectionWidget(QWidget *parent = nullptr);
     virtual ~ConnectionWidget();
 
     QSqlDatabase currentDatabase() const;
diff --git a/examples/sql/sqlbrowser/main.cpp b/examples/sql/sqlbrowser/main.cpp
index 002dbc3242..ea4649b68d 100644
--- a/examples/sql/sqlbrowser/main.cpp
+++ b/examples/sql/sqlbrowser/main.cpp
@@ -80,16 +80,18 @@ int main(int argc, char *argv[])
     mainWin.setCentralWidget(&browser);
 
     QMenu *fileMenu = mainWin.menuBar()->addMenu(QObject::tr("&File"));
-    fileMenu->addAction(QObject::tr("Add &Connection..."), &browser, SLOT(addConnection()));
+    fileMenu->addAction(QObject::tr("Add &Connection..."),
+            [&]() { browser.addConnection(); });
     fileMenu->addSeparator();
-    fileMenu->addAction(QObject::tr("&Quit"), &app, SLOT(quit()));
+    fileMenu->addAction(QObject::tr("&Quit"), []() { qApp->quit(); });
 
     QMenu *helpMenu = mainWin.menuBar()->addMenu(QObject::tr("&Help"));
-    helpMenu->addAction(QObject::tr("About"), &browser, SLOT(about()));
-    helpMenu->addAction(QObject::tr("About Qt"), qApp, SLOT(aboutQt()));
+    helpMenu->addAction(QObject::tr("About"), [&]() { browser.about(); });
+    helpMenu->addAction(QObject::tr("About Qt"), []() { qApp->aboutQt(); });
 
-    QObject::connect(&browser, SIGNAL(statusMessage(QString)),
-                     mainWin.statusBar(), SLOT(showMessage(QString)));
+    QObject::connect(&browser, &Browser::statusMessage, [&mainWin](const QString &text) {
+        mainWin.statusBar()->showMessage(text);
+    });
 
     addConnectionsFromCommandline(app.arguments(), &browser);
     mainWin.show();
diff --git a/examples/sql/sqlbrowser/qsqlconnectiondialog.h b/examples/sql/sqlbrowser/qsqlconnectiondialog.h
index d43955acdc..fc998d7ee9 100644
--- a/examples/sql/sqlbrowser/qsqlconnectiondialog.h
+++ b/examples/sql/sqlbrowser/qsqlconnectiondialog.h
@@ -60,7 +60,7 @@ class QSqlConnectionDialog: public QDialog
 {
     Q_OBJECT
 public:
-    QSqlConnectionDialog(QWidget *parent = 0);
+    QSqlConnectionDialog(QWidget *parent = nullptr);
     ~QSqlConnectionDialog();
 
     QString driverName() const;
diff --git a/examples/sql/sqlwidgetmapper/window.cpp b/examples/sql/sqlwidgetmapper/window.cpp
index 21ce152169..b6946e2386 100644
--- a/examples/sql/sqlwidgetmapper/window.cpp
+++ b/examples/sql/sqlwidgetmapper/window.cpp
@@ -87,12 +87,12 @@ Window::Window(QWidget *parent)
 //! [Set up the mapper]
 
 //! [Set up connections and layouts]
-    connect(previousButton, SIGNAL(clicked()),
-            mapper, SLOT(toPrevious()));
-    connect(nextButton, SIGNAL(clicked()),
-            mapper, SLOT(toNext()));
-    connect(mapper, SIGNAL(currentIndexChanged(int)),
-            this, SLOT(updateButtons(int)));
+    connect(previousButton, &QPushButton::clicked,
+            mapper, &QDataWidgetMapper::toPrevious);
+    connect(nextButton, &QPushButton::clicked,
+            mapper, &QDataWidgetMapper::toNext);
+    connect(mapper, &QDataWidgetMapper::currentIndexChanged,
+            this, &Window::updateButtons);
 
     QGridLayout *layout = new QGridLayout();
     layout->addWidget(nameLabel, 0, 0, 1, 1);
diff --git a/examples/sql/sqlwidgetmapper/window.h b/examples/sql/sqlwidgetmapper/window.h
index bff074d954..b336997360 100644
--- a/examples/sql/sqlwidgetmapper/window.h
+++ b/examples/sql/sqlwidgetmapper/window.h
@@ -72,7 +72,7 @@ class Window : public QWidget
     Q_OBJECT
 
 public:
-    Window(QWidget *parent = 0);
+    Window(QWidget *parent = nullptr);
 
 private slots:
     void updateButtons(int row);
diff --git a/examples/sql/tablemodel/tablemodel.cpp b/examples/sql/tablemodel/tablemodel.cpp
index c22e25cbef..a6e0341c23 100644
--- a/examples/sql/tablemodel/tablemodel.cpp
+++ b/examples/sql/tablemodel/tablemodel.cpp
@@ -47,11 +47,13 @@
 ** $QT_END_LICENSE$
 **
 ****************************************************************************/
+#include "../connection.h"
 
-#include <QtWidgets>
-#include <QtSql>
+#include <QApplication>
+#include <QSqlTableModel>
+#include <QTableView>
 
-#include "../connection.h"
+#include <stdlib.h>
 
 void initializeModel(QSqlTableModel *model)
 {
@@ -76,7 +78,7 @@ int main(int argc, char *argv[])
 {
     QApplication app(argc, argv);
     if (!createConnection())
-        return 1;
+        return EXIT_FAILURE;
 
     QSqlTableModel model;