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Using QDataWidgetMapper to show data from a database in Qt

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Article Metadata
Tested with
SDK: Qt "tower" pre-release
Devices(s): Nokia 5800 XpressMusic, Nokia N900
Compatibility
Platform(s): Qt
Symbian
Article
Keywords: QSqlDatabase, QSQlite, QSqlTableModel, QDataWidgetMapper
Created: tepaa (25 Nov 2009)
Last edited: hamishwillee (11 Oct 2012)

Contents

Overview

This example shows you how to map a UI component to a database table using QSqlTableModel and QDataWidgetMapper in Qt. Searching and updating data can be done without using any SQL statements.

The table 'person' has the following columns:

  • id (integer primary key), this is an autoincrement field
  • firstname (varchar(20))
  • lastname (varchar(30))
  • age (integer)


Preconditions

For Maemo SQLite development, the following packages must be installed:

  • libqt4-sql
  • libqt4-sql-sqlite
  • libsqlite3-0
  • libsqlite3-dev


Header

Dialog for showing and updating a person's last name:

#include <QtGui>
#include <QtSql>
 
class MyDialog : public QDialog
{
Q_OBJECT
 
public:
MyDialog(int id = 0, QWidget *parent = 0);
~MyDialog();
 
public slots:
void save();
 
private:
// "person" table mode class
QSqlTableModel* tableModel;
 
// Maps QLineEdit ui control into "person"
// table's lastname field
QDataWidgetMapper* dataMapper;
 
QVBoxLayout* vboxlayout;
QLineEdit* nameLineEdit;
QPushButton* saveButton;
};


Source

MyDialog::MyDialog(int id, QWidget *parent)
: QDialog(parent)
{
vboxlayout = new QVBoxLayout(this);
 
nameLineEdit = new QLineEdit(this);
nameLineEdit->setContextMenuPolicy(Qt::NoContextMenu);
nameLineEdit->setAlignment(Qt::AlignTop);
vboxlayout->addWidget(nameLineEdit);
 
saveButton = new QPushButton("Save",this);
saveButton->setFixedHeight(60);
QObject::connect(saveButton, SIGNAL(clicked()), this, SLOT(save()));
vboxlayout->addWidget(saveButton);
 
// 'person' table model
tableModel = new QSqlTableModel(this);
tableModel->setTable("person");
// Set where clause
// QLineEdit shows person lastname that id is given parameter
tableModel->setFilter(QString("id=%1").arg(id));
tableModel->select();
 
// Maps QLineEdit ui control into "person" table's lastname field
dataMapper = new QDataWidgetMapper(this);
dataMapper->setModel(tableModel);
// We want that data is stored only if we call QDataWidgetMapper::submit()
dataMapper->setSubmitPolicy(QDataWidgetMapper::ManualSubmit);
dataMapper->setItemDelegate(new QSqlRelationalDelegate(dataMapper));
dataMapper->addMapping(nameLineEdit, tableModel->fieldIndex("lastname"));
dataMapper->toFirst();
 
setLayout(vboxlayout);
}
 
MyDialog::~MyDialog()
{
}
 
 
void MyDialog::save()
{
// Stores data from QLineEdit to database using QDataWidgetMapper
dataMapper->submit();
}


Postconditions

The UI controls get data from the database and the data can be updated via controls without using any SQL statements.


See also

This page was last modified on 11 October 2012, at 04:16.
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