window.cpp Example File

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 #include <QtWidgets>
 #include <QtSql>

 #include "window.h"

 Window::Window(QWidget *parent)
     : QWidget(parent)
 {
     setupModel();

     nameLabel = new QLabel(tr("Na&me:"));
     nameEdit = new QLineEdit();
     addressLabel = new QLabel(tr("&Address:"));
     addressEdit = new QTextEdit();
     typeLabel = new QLabel(tr("&Type:"));
     typeComboBox = new QComboBox();
     nextButton = new QPushButton(tr("&Next"));
     previousButton = new QPushButton(tr("&Previous"));

     nameLabel->setBuddy(nameEdit);
     addressLabel->setBuddy(addressEdit);
     typeLabel->setBuddy(typeComboBox);

     QSqlTableModel *relModel = model->relationModel(typeIndex);
     typeComboBox->setModel(relModel);
     typeComboBox->setModelColumn(relModel->fieldIndex("description"));

     mapper = new QDataWidgetMapper(this);
     mapper->setModel(model);
     mapper->setItemDelegate(new QSqlRelationalDelegate(this));
     mapper->addMapping(nameEdit, model->fieldIndex("name"));
     mapper->addMapping(addressEdit, model->fieldIndex("address"));
     mapper->addMapping(typeComboBox, typeIndex);

     connect(previousButton, SIGNAL(clicked()),
             mapper, SLOT(toPrevious()));
     connect(nextButton, SIGNAL(clicked()),
             mapper, SLOT(toNext()));
     connect(mapper, SIGNAL(currentIndexChanged(int)),
             this, SLOT(updateButtons(int)));

     QGridLayout *layout = new QGridLayout();
     layout->addWidget(nameLabel, 0, 0, 1, 1);
     layout->addWidget(nameEdit, 0, 1, 1, 1);
     layout->addWidget(previousButton, 0, 2, 1, 1);
     layout->addWidget(addressLabel, 1, 0, 1, 1);
     layout->addWidget(addressEdit, 1, 1, 2, 1);
     layout->addWidget(nextButton, 1, 2, 1, 1);
     layout->addWidget(typeLabel, 3, 0, 1, 1);
     layout->addWidget(typeComboBox, 3, 1, 1, 1);
     setLayout(layout);

     setWindowTitle(tr("SQL Widget Mapper"));
     mapper->toFirst();
 }

 void Window::setupModel()
 {
     QSqlDatabase db = QSqlDatabase::addDatabase("QSQLITE");
     db.setDatabaseName(":memory:");
     if (!db.open()) {
         QMessageBox::critical(0, tr("Cannot open database"),
             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."), QMessageBox::Cancel);
         return;
     }

     QSqlQuery query;
     query.exec("create table person (id int primary key, "
                "name varchar(20), address varchar(200), typeid int)");
     query.exec("insert into person values(1, 'Alice', "
                "'<qt>123 Main Street<br/>Market Town</qt>', 101)");
     query.exec("insert into person values(2, 'Bob', "
                "'<qt>PO Box 32<br/>Mail Handling Service"
                "<br/>Service City</qt>', 102)");
     query.exec("insert into person values(3, 'Carol', "
                "'<qt>The Lighthouse<br/>Remote Island</qt>', 103)");
     query.exec("insert into person values(4, 'Donald', "
                "'<qt>47338 Park Avenue<br/>Big City</qt>', 101)");
     query.exec("insert into person values(5, 'Emma', "
                "'<qt>Research Station<br/>Base Camp<br/>"
                "Big Mountain</qt>', 103)");

     query.exec("create table addresstype (id int, description varchar(20))");
     query.exec("insert into addresstype values(101, 'Home')");
     query.exec("insert into addresstype values(102, 'Work')");
     query.exec("insert into addresstype values(103, 'Other')");

     model = new QSqlRelationalTableModel(this);
     model->setTable("person");
     model->setEditStrategy(QSqlTableModel::OnManualSubmit);

     typeIndex = model->fieldIndex("typeid");

     model->setRelation(typeIndex,
            QSqlRelation("addresstype", "id", "description"));
     model->select();
 }

 void Window::updateButtons(int row)
 {
     previousButton->setEnabled(row > 0);
     nextButton->setEnabled(row < model->rowCount() - 1);
 }