C++/Qt/QFile — различия между версиями
Admin (обсуждение | вклад) м (1 версия: Импорт контента...) |
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(нет различий)
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Текущая версия на 13:25, 25 мая 2010
Содержание
- 1 Check file existance and file name with QFile
- 2 Create file with QFile
- 3 Create QFile from file path
- 4 Open a text file in read-only mode
- 5 Open binary file for write-operation
- 6 Open QFile with WriteOnly flag
- 7 Open text file for write-operation
- 8 Output with QFile
- 9 Read byte array from text file
- 10 Read file till file end
- 11 Read text file line by line
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. * */
- include <QFile>
- 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. * */
- include <QFile>
- include <QDataStream>
- include <QList>
- include <QColor>
- 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.
- $QT_END_LICENSE$
-
- /
- include <QFile>
- 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.
- $QT_END_LICENSE$
-
- /
- include <QFile>
- 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">
- include <QFile>
- 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. * */
- include <QFile>
- 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">
- include <QFile>
- 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">
- include <QtCore>
- include <iostream>
- 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.
- $QT_END_LICENSE$
-
- /
- include <QFile>
- 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.
- $QT_END_LICENSE$
-
- /
- include <QFile>
- 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.
- $QT_END_LICENSE$
-
- /
- include <QFile>
- 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>