C++/Qt/QObject

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cpp with qobject

  
/*
 * Copyright (c) 2006-2007, Johan Thelin
 * 
 * All rights reserved.
 * 
 * Redistribution and use in source and binary forms, with or without modification, 
 * are permitted provided that the following conditions are met:
 * 
 *     * Redistributions of source code must retain the above copyright notice, 
 *       this list of conditions and the following disclaimer.
 *     * Redistributions in binary form must reproduce the above copyright notice,  
 *       this list of conditions and the following disclaimer in the documentation 
 *       and/or other materials provided with the distribution.
 *     * Neither the name of APress nor the names of its contributors 
 *       may be used to endorse or promote products derived from this software 
 *       without specific prior written permission.
 * 
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
 * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
 * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 *
 */
 
#include <string>
using namespace std;
#include <QtDebug>
#include <QObject>
class MyClass : public QObject
{
public:
  MyClass( const string &text, QObject *parent = 0 );
  const string &text();
  void setText( const string &text );
  int getLengthOfText();
  
private:
  string m_text;
};
MyClass::MyClass( const string &text, QObject *parent ) : QObject( parent )
{
  m_text = text;
}
const string &MyClass::text() { return m_text; }
void MyClass::setText( const string &text ) { m_text = text; }
int MyClass::getLengthOfText() { return m_text.size(); }
int main( int argc, char **argv )
{
  QObject parent;
  MyClass *a, *b, *c;
  a = new MyClass( "foo", &parent );
  b = new MyClass( "ba-a-ar", &parent );
  c = new MyClass( "baz", &parent );
  qDebug() << QString::fromStdString(a->text()) << " (" << a->getLengthOfText() << ")";
  a->setText( b->text() );
  qDebug() << QString::fromStdString(a->text()) << " (" << a->getLengthOfText() << ")";
  return a->getLengthOfText() - c->getLengthOfText();
}


Qt cast

  
/****************************************************************************
**
** Copyright (C) 2009 Nokia Corporation and/or its subsidiary(-ies).
** All rights reserved.
** Contact: Nokia Corporation (qt-info@nokia.com)
**
** This file is part of the documentation of the Qt Toolkit.
**
** $QT_BEGIN_LICENSE:LGPL$
** Commercial Usage
** Licensees holding valid Qt Commercial licenses may use this file in
** accordance with the Qt Commercial License Agreement provided with the
** Software or, alternatively, in accordance with the terms contained in
** a written agreement between you and Nokia.
**
** GNU Lesser General Public License Usage
** Alternatively, this file may be used under the terms of the GNU Lesser
** General Public License version 2.1 as published by the Free Software
** Foundation and appearing in the file LICENSE.LGPL included in the
** packaging of this file.  Please review the following information to
** ensure the GNU Lesser General Public License version 2.1 requirements
** will be met: http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html.
**
** In addition, as a special exception, Nokia gives you certain additional
** rights.  These rights are described in the Nokia Qt LGPL Exception
** version 1.1, included in the file LGPL_EXCEPTION.txt in this package.
**
** GNU General Public License Usage
** Alternatively, this file may be used under the terms of the GNU
** General Public License version 3.0 as published by the Free Software
** Foundation and appearing in the file LICENSE.GPL included in the
** packaging of this file.  Please review the following information to
** ensure the GNU General Public License version 3.0 requirements will be
** met: http://www.gnu.org/copyleft/gpl.html.
**
** If you have questions regarding the use of this file, please contact
** Nokia at qt-info@nokia.com.
** $QT_END_LICENSE$
**
****************************************************************************/
#ifndef QTCAST_H
#define QTCAST_H
#include <QWidget>
class MyWidget : public QWidget
{
    Q_OBJECT
public:
    MyWidget();
};
#endif





#include <QLabel>
#include <QPushButton>
#include "qtcast.h"
MyWidget::MyWidget()
{
    QObject *obj = new MyWidget;

    QWidget *widget = qobject_cast<QWidget *>(obj);

    MyWidget *myWidget = qobject_cast<MyWidget *>(obj);

    QLabel *label = qobject_cast<QLabel *>(obj);
 
    // label is 0

    if (QLabel *label = qobject_cast<QLabel *>(obj)) {
 
        label->setText(tr("Ping"));
    } else if (QPushButton *button = qobject_cast<QPushButton *>(obj)) {
        button->setText(tr("Pong!"));
    }
}
int main()
{
    return 0;
}