Validators

In this example you see how to write and use an own validator.

---

Header file of the validator:

/****************************************************************************
** $Id: //depot/qt/main/examples/validator/motor.h#3 $
**
** Copyright (C) 1992-2000 Trolltech AS.  All rights reserved.
**
** This file is part of an example program for Qt.  This example
** program may be used, distributed and modified without limitation.
**
*****************************************************************************/

#ifndef MOTOR_H
#define MOTOR_H

#include <qvalidator.h>
#include <qspinbox.h>

class MotorValidator: public QValidator
{
    Q_OBJECT
public:
    MotorValidator( QSpinBox * parent, const char * name );
    ~MotorValidator();

    void setRange( int bottom, int top, int step );

    int bottom() { return b; }
    int top() { return t; }
    int step() { return s; }

    QValidator::State validate( QString &, int & ) const;

private:
    int b, t, s;
};

#endif

---

Implementation of the validator:

/****************************************************************************
** $Id: //depot/qt/main/examples/validator/motor.cpp#3 $
**
** Copyright (C) 1992-2000 Trolltech AS.  All rights reserved.
**
** This file is part of an example program for Qt.  This example
** program may be used, distributed and modified without limitation.
**
*****************************************************************************/

#include "motor.h"
#include "qlineedit.h"
#include "qpushbutton.h"

MotorValidator::MotorValidator( QSpinBox * parent, const char * name )
    : QValidator( parent, name )
{
    // just some random junk.
    b = 0;
    t = 42;
    s = 2;
}

MotorValidator::~MotorValidator()
{
    // nothing.  wow. programming qt is easy.
}

void MotorValidator::setRange( int bottom, int top, int step )
{
    b = bottom;
    t = top;
    s = step;
}

// the guts of this example: return TRUE if motorSize describes an
// integer in the range b to t which can be described as n*s+b for
// some integer n.

QValidator::State MotorValidator::validate( QString & motorSize, int & ) const
{
    bool ok;
    long int tmp = motorSize.toLong( &ok );
    if ( !ok )
        return QValidator::Invalid;
    else if ( tmp < b || tmp > t || ((tmp-b)%s) != 0 )
        return QValidator::Valid;
    else
        return QValidator::Acceptable;
}

---

Header file of the mainwidget:

/****************************************************************************
** $Id: //depot/qt/main/examples/validator/vw.h#2 $
**
** Copyright (C) 1992-2000 Trolltech AS.  All rights reserved.
**
** This file is part of an example program for Qt.  This example
** program may be used, distributed and modified without limitation.
**
*****************************************************************************/

#ifndef VW_H
#define VW_H

#include <qvalidator.h>
#include <qstring.h>
#include <qwidget.h>

class VW: public QWidget {
    Q_OBJECT
public:
    VW( QWidget * parent = 0, const char * name = 0 );
    ~VW();

private slots:
    void modelSelected( const QString& );
    void motorSelected( int );
    void yearSelected( int );

signals:
    void validSelectionMade( const QString& );

private:
    void computeSelection();

    QString currentModel;
    int currentMotorSize;
    int currentYear;
};

#endif

---

Implementation of the mainwidget:

/****************************************************************************
** $Id: //depot/qt/main/examples/validator/vw.cpp#2 $
**
** Copyright (C) 1992-2000 Trolltech AS.  All rights reserved.
**
** This file is part of an example program for Qt.  This example
** program may be used, distributed and modified without limitation.
**
*****************************************************************************/

#include "vw.h"

#include <qlineedit.h>
#include <qcombobox.h>
#include <qspinbox.h>
#include <qlayout.h>
#include <qgroupbox.h>
#include <qlabel.h>

#include "motor.h"

VW::VW( QWidget * parent, const char * name )
    : QWidget( parent, name )
{
    QHBoxLayout * hb;

    hb = new QHBoxLayout( this, 10 );

    QGroupBox * box;
    box = new QGroupBox( this, "input box" );
    hb->addWidget( box, 0, AlignTop );

    QVBoxLayout * b;

    // set up the input box
    b = new QVBoxLayout( box, 12 );

    QLabel * l = new QLabel( "Enter Vehicle Details", box, "header" );
    l->setMinimumSize( l->sizeHint() );
    b->addWidget( l );
    QFrame * f = new QFrame( box, "horizontal divider" );
    f->setFrameStyle( QFrame::HLine | QFrame::Sunken );
    f->setMinimumHeight( 12 );
    b->addWidget( f );

    QGridLayout *grid = new QGridLayout( 3, 2 );
    b->addLayout( grid );

    // here we start on the input grid, with labels and other widget
    // neatly arranged. the variable names are reused all over the
    // place.

    QComboBox * model = new QComboBox( FALSE, box, "model selection" );
    model->insertItem( "Type 1 Beetle" );
    model->insertItem( "Camper" );
    model->insertItem( "Van" );
    model->insertItem( "Fastback" );
    model->insertItem( "Squareback" );
    model->insertItem( "Notchback" );
    model->insertItem( "411" );
    model->setCurrentItem( model->count() - 1 ); // I like the 411
    currentModel = "411";
    model->insertItem( "412" );
    model->insertItem( "Karmann Ghia" );
    model->insertItem( "Thing" );
    model->insertItem( "Safari" );
    model->insertItem( "Kubelwagen" );
    model->insertItem( "Trekker" );
    model->insertItem( "Baja" );
    model->setMinimumSize( model->sizeHint() );
    model->setMaximumHeight( model->minimumSize().height() );
    grid->addWidget( model, 0, 1 );

    l = new QLabel( model, "Model:", box, "model label" );
    l->setMinimumSize( l->sizeHint() );
    grid->addWidget( l, 0, 0 );

    QSpinBox * motor = new QSpinBox( 1000, 1600, 100,
                                     box, "motor size selection" );
    motor->setValue( 1000 );
    currentMotorSize = 1000;
    motor->setMinimumSize( motor->sizeHint() );
    motor->setMaximumHeight( motor->minimumSize().height() );
    grid->addWidget( motor, 1, 1 );

    l = new QLabel( motor, "Motor size (cc):", box, "motor size label" );
    l->setMinimumSize( l->sizeHint() );
    grid->addWidget( l, 1, 0 );

    QSpinBox * year = new QSpinBox( box, "model year" );
    year->setRange( 1949, 1981 );
    year->setValue( 1949 );
    currentYear = 1949;
    year->setMinimumSize( year->sizeHint() );
    year->setMaximumHeight( year->minimumSize().height() );
    grid->addWidget( year, 2, 1 );

    l = new QLabel( year, "Year:", box, "model year label" );
    l->setMinimumSize( l->sizeHint() );
    grid->addWidget( l, 2, 0 );

    b->addStretch( 1 );

    b->activate();

    // output box

    box = new QGroupBox( this, "output box" );
    hb->addWidget( box, 0 );

    b = new QVBoxLayout( box, 12 );

    l = new QLabel( "Resulting Limousine:", box, "header" );
    l->setMinimumSize( l->sizeHint() );
    b->addWidget( l );

    f = new QFrame( box, "horizontal divider" );
    f->setFrameStyle( QFrame::HLine | QFrame::Sunken );
    f->setMinimumHeight( 12 );
    b->addWidget( f );

    l = new QLabel( box, "output label" );
    l->setAlignment( AlignTop | AlignLeft | WordBreak );
    l->setText( "No VW selected yet." );
    b->addWidget( l, 1 );

    b->addStretch( 1 );

    b->activate();
    hb->activate();

    // set up connections
    connect( model, SIGNAL(activated(const QString&)),
             this, SLOT(modelSelected(const QString&)) );
    connect( motor, SIGNAL(valueChanged(int)),
             this, SLOT(motorSelected(int)) );
    connect( year, SIGNAL(valueChanged(int)),
             this, SLOT(yearSelected(int)) );

    connect( this, SIGNAL(validSelectionMade(const QString&)),
             l, SLOT(setText(const QString&)) );
}

VW::~VW()
{
    // nothing needs to be done.
}

void VW::modelSelected( const QString& m )
{
    currentModel = m;
    computeSelection();
}

void VW::motorSelected( int m )
{
    currentMotorSize = m;
    computeSelection();
}

void VW::yearSelected( int y )
{
    currentYear = y;
    computeSelection();
}

void VW::computeSelection()
{
    if ( currentModel.isNull() )
        return; // no model selected yet

    QString s;
    s.sprintf( "You have selected a Volkswagen %s model %d with a "
               "%d cm³ motor.\n\nGood choice!",
               (const char *)currentModel,
               (int)currentYear, currentMotorSize );
    emit validSelectionMade( s );
}

---

Main:

/****************************************************************************
** $Id: //depot/qt/main/examples/validator/main.cpp#2 $
**
** Copyright (C) 1992-2000 Trolltech AS.  All rights reserved.
**
** This file is part of an example program for Qt.  This example
** program may be used, distributed and modified without limitation.
**
*****************************************************************************/

#include <qapplication.h>
#include "vw.h"

int main( int argc, char ** argv ) {
    QApplication a( argc, argv );
    VW mw;
    a.setMainWidget( &mw );
    mw.setCaption( "Qt Example - Validators" );
    mw.show();
    return a.exec();
}