C++/Qt/QFile — различия между версиями

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Версия 17:21, 25 мая 2010

Check file existance and file name with QFile

<source lang="cpp"> Foundations of Qt Development\Chapter08\fileexist\main.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 <QFile>
  2. include <QtDebug>

int main( int argc, char **argv ) { 

 QFile file( "testfile.txt" );
 
 if( !file.exists() )
 {
   qDebug() << "The file" << file.fileName() << "does not exist.";
   return 0;
 }
 
 if( !file.open( QIODevice::WriteOnly ) )
 {
   qDebug() << "Could not open" << file.fileName() << "for writing.";
   return 0;
 }
 
 qDebug() << "The file opened.";
 
 file.close();
 
 return 0;

} 


 </source>


Create file with QFile

<source lang="cpp">

Foundations of Qt Development\Chapter08\datastream\main.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 <QFile>
  2. include <QDataStream>
  3. include <QList>
  4. include <QColor>
  5. include <QtDebug>

struct ColorText { 

 QString text;
 QColor color;

}; QDataStream &operator<<( QDataStream &stream, const ColorText &data ) { 

 stream << data.text << data.color;
 
 return stream;

} QDataStream &operator>>( QDataStream &stream, ColorText &data ) { 

 stream >> data.text;
 stream >> data.color;
 
 return stream;

} void saveList() { 

 QList<ColorText> list;
 ColorText data;
 
 data.text = "Red";
 data.color = Qt::red;
 list << data;
 
 data.text = "Blue";
 data.color = Qt::blue;
 list << data;
 data.text = "Yellow";
 data.color = Qt::yellow;
 list << data;
 data.text = "Green";
 data.color = Qt::green;
 list << data;
 
 QFile file( "test.dat" );
 if( !file.open( QIODevice::WriteOnly ) )
   return;
   
 QDataStream stream( &file );
 stream.setVersion( QDataStream::Qt_4_2 );
 
 stream << list;
 
 file.close();

} void loadList() { 

 QList<ColorText> list;
 
 QFile file( "test.dat" );
 if( !file.open( QIODevice::ReadOnly ) )
   return;
   
 QDataStream stream( &file );
 stream.setVersion( QDataStream::Qt_4_2 );
 stream >> list;
 
 file.close();
 foreach( ColorText data, list )
   qDebug() << data.text << "(" 
            << data.color.red() << "," 
            << data.color.green() << "," 
            << data.color.blue() << ")";

} int main( int argc, char **argv ) { 

 saveList();
 loadList();
 
 return 0;

} 


 </source>


Create QFile from file path

<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. include <QFile>
  2. include <QTextStream>

static void process_line(const QByteArray &) { } static void process_line(const QString &) { } int main() { 

   QFile file("in.txt");
   if (!file.open(QIODevice::ReadOnly | QIODevice::Text))
       return 1;
   while (!file.atEnd()) {
       QByteArray line = file.readLine();
       process_line(line);
   }

} 


 </source>


Open a text file in read-only mode

<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. include <QFile>
  2. include <QTextStream>

static void process_line(const QByteArray &) { } static void process_line(const QString &) { } int main() { 

   QFile file("in.txt");
   if (!file.open(QIODevice::ReadOnly | QIODevice::Text))
       return 1;
   while (!file.atEnd()) {
       QByteArray line = file.readLine();
       process_line(line);
   }

} 


 </source>


Open binary file for write-operation

<source lang="cpp">

  1. include <QFile>
  2. include <QTextStream>

int main() { 

   QFile file("out.dat");
   if (!file.open(QIODevice::WriteOnly))
       return 1;
   QDataStream out(&file);
   out << "The magic number is: " << 49 << "\n";

} 


 </source>


Open QFile with WriteOnly flag

<source lang="cpp">

Foundations of Qt Development\Chapter08\fileexist\main.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 <QFile>
  2. include <QtDebug>

int main( int argc, char **argv ) { 

 QFile file( "testfile.txt" );
 
 if( !file.exists() )
 {
   qDebug() << "The file" << file.fileName() << "does not exist.";
   return 0;
 }
 
 if( !file.open( QIODevice::WriteOnly ) )
 {
   qDebug() << "Could not open" << file.fileName() << "for writing.";
   return 0;
 }
 
 qDebug() << "The file opened.";
 
 file.close();
 
 return 0;

} 


 </source>


Open text file for write-operation

<source lang="cpp">

  1. include <QFile>
  2. include <QTextStream>

int main() { 

   QFile file("out.txt");
   if (!file.open(QIODevice::WriteOnly | QIODevice::Text))
       return 1;
   QTextStream out(&file);
   out << "The magic number is: " << 49 << "\n";

} 


 </source>


Output with QFile

<source lang="cpp">

  1. include <QtCore>
  2. include <iostream>
  3. include <stdio.h>

using namespace std; int main(int argc, char* argv[]) { 

 QFile in("c:\\a.txt");
 if(!in.open(QIODevice::ReadOnly|QIODevice::Text)) {
   cerr << "File " << argv[1] << " does not exist" << endl;
 }
 QFile out;
 out.setFileName(argv[2]);
 if (out.exists()) {
     cerr << "File" << argv[2] << " already exists" << endl;
     return 1;
 }
 if(!out.open(QIODevice::WriteOnly|QIODevice::Text)) {
     cerr << "Failed to open file " << argv[2] << " for writing" << endl;
     return 1;
 }
 while (!in.atEnd()) {
  QByteArray line = in.readLine();
  if (!line.trimmed().isEmpty() && !line.trimmed().startsWith("#"))
    out.write(line);
 }
 in.close();
 out.close();
 return 0;

} 


 </source>


Read byte array from text file

<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. include <QFile>
  2. include <QTextStream>

static void process_line(const QByteArray &) { } static void process_line(const QString &) { } int main() { 

   QFile file("in.txt");
   if (!file.open(QIODevice::ReadOnly | QIODevice::Text))
       return 1;
   while (!file.atEnd()) {
       QByteArray line = file.readLine();
       process_line(line);
   }

} 


 </source>


Read file till file end

<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. include <QFile>
  2. include <QTextStream>

static void process_line(const QByteArray &) { } static void process_line(const QString &) { } int main() { 

   QFile file("in.txt");
   if (!file.open(QIODevice::ReadOnly | QIODevice::Text))
       return 1;
   while (!file.atEnd()) {
       QByteArray line = file.readLine();
       process_line(line);
   }

} 


 </source>


Read text file line by line

<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. include <QFile>
  2. include <QTextStream>

static void process_line(const QByteArray &) { } static void process_line(const QString &) { } int main() { 

   QFile file("modules");
   if (!file.open(QIODevice::ReadOnly | QIODevice::Text))
       return 1;
   QTextStream in(&file);
   QString line = in.readLine();
   while (!line.isNull()) {
       process_line(line);
       line = in.readLine();
   }

} 


 </source>
Источник — «http://cppe.ru/index.php?title=C%2B%2B/Qt/QFile&oldid=1168»