C++/Qt/QObject

cpp with qobject

<source lang="cpp"> /*

* 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.
*
*/

1. include <string>

using namespace std;

1. include <QtDebug>
2. 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();

}

 </source>

Qt cast

<source lang="cpp"> /****************************************************************************

• • 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.
  • $QT_END_LICENSE$
  • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • /

1. ifndef QTCAST_H
2. define QTCAST_H
3. include <QWidget>

class MyWidget : public QWidget {

   Q_OBJECT

public:

   MyWidget();

};

1. endif

1. include <QLabel>
2. include <QPushButton>
3. 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;

}

 </source>