(Qt) 文件读写基础

文章目录

• 🗂️前言
• • 📄ref
  • 📄访问标记
  • • 🗃️enum 标记
• 🗂️Code
• • 📄demo
  • 📄分点讲解
  • • 🗃️继承体系
    • 🗃️打开/关闭
    • 🗃️写
    • 🗃️读
• 🗂️END
• • 🌟关注我

🗂️前言

📄ref

• Index of / (qt.io)

本文资料和测试版本为 Qt 5.15

📄访问标记

🗃️enum 标记

std::ios_base::openmode - cppreference.com

class QIODevice;  	enum OpenModeFlag {         NotOpen = 0x0000,         ReadOnly = 0x0001,         WriteOnly = 0x0002,         ReadWrite = ReadOnly | WriteOnly,         Append = 0x0004,         Truncate = 0x0008,         Text = 0x0010,         Unbuffered = 0x0020,         NewOnly = 0x0040,         ExistingOnly = 0x0080     };     Q_DECLARE_FLAGS(OpenMode, OpenModeFlag) 

class QFileDevice;      enum FileError {         NoError = 0,         ReadError = 1,         WriteError = 2,         FatalError = 3,         ResourceError = 4,         OpenError = 5,         AbortError = 6,         TimeOutError = 7,         UnspecifiedError = 8,         RemoveError = 9,         RenameError = 10,         PositionError = 11,         ResizeError = 12,         PermissionsError = 13,         CopyError = 14     };      enum FileTime {         FileAccessTime,         FileBirthTime,         FileMetadataChangeTime,         FileModificationTime     };      enum Permission {         ReadOwner = 0x4000, WriteOwner = 0x2000, ExeOwner = 0x1000,         ReadUser  = 0x0400, WriteUser  = 0x0200, ExeUser  = 0x0100,         ReadGroup = 0x0040, WriteGroup = 0x0020, ExeGroup = 0x0010,         ReadOther = 0x0004, WriteOther = 0x0002, ExeOther = 0x0001     };     Q_DECLARE_FLAGS(Permissions, Permission)      enum FileHandleFlag {         AutoCloseHandle = 0x0001,         DontCloseHandle = 0     };     Q_DECLARE_FLAGS(FileHandleFlags, FileHandleFlag) 

🗂️Code

📄demo

qmake

QT += core  #DESTDIR = $$PWD/bin CONFIG += c++11 console  SOURCES += \         main.cpp 

main.cpp

#include <QDebug> #include <QFile> #include <QString>  void check_qfile(QFile& file) {     qWarning() << file.error() << file.errorString(); }  void file_write(QString file_path) {     QFile file(file_path);     if (file.open(QFile::WriteOnly) == false) {         qDebug() << __func__;         check_qfile(file);         return;     }      QString name = "cuber-lotus";     QString url  = "https://space.bilibili.com/8172252";     /// QTextStream &endl(QTextStream &s)     QTextStream(&file) << name << Qt::endl;     /// QString -> QByteArray     file.write(url.toLocal8Bit());      qDebug() << __func__;     check_qfile(file);     file.close(); }  void file_read(QString file_path) {     QFile file(file_path);     if (file.open(QFile::ReadOnly) == false) {         qDebug() << __func__;         check_qfile(file);         return;     }      /// 直接读取全部     /// QByteArray -> QString     QByteArray byteArr = file.readAll();     QString    msg     = byteArr;     qDebug().noquote() << msg;      qDebug() << __func__;     check_qfile(file);     file.close(); }  int main() {     QString file_path = "example.txt";     file_write(file_path);     file_read(file_path); } 

📄分点讲解

🗃️继承体系

QIODevice是否继承于QObject取决于是否指定（编译时指定）。

#################### ####  QIODevice  ###  ####################         | 	    V #################### #### QFileDevice ###  ####################         | 	    V #################### ####    QFile    ###  #################### 

🗃️打开/关闭

QFile file(file_path); if (file.open(QFile::WriteOnly) == false) {     return; } 

🗃️写

法1：

// 借助 QTextStream qt的文件流操作 QString name = "cuber-lotus"; /// QTextStream &endl(QTextStream &s) QTextStream(&file) << name << Qt::endl; 

法2：

// 使用自带的 write QString url  = "https://space.bilibili.com/8172252"; /// QString -> QByteArray file.write(url.toLocal8Bit()); 

qint64 write(const char *data, qint64 len); qint64 write(const char *data); inline qint64 write(const QByteArray &data) { return write(data.constData(), data.size()); } 

🗃️读

• read
• reanLine
• readAll

qint64 read(char *data, qint64 maxlen); QByteArray read(qint64 maxlen); QByteArray readAll(); qint64 readLine(char *data, qint64 maxlen); QByteArray readLine(qint64 maxlen = 0); virtual bool canReadLine() const; 

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🗂️END

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