Day12QFile2021-09-27

QFile—— File operations

Qt The file operation of is very simple ,Qt Provided in the QIODevice Class as all I/O Equipment foundation interface , by IO Equipment such as QFile Provides an abstract interface .QFile Is a readable and writable text file 、 Binary 、 as well as qt Of resource files IO equipment . Before accessing a device , Need to use open（） Function to open the device , And the correct opening mode must be established . Use write（）、putchar Method write ,read（）,readline（）、readAll（） Method read , with QTextStream or QDataStream Use a combination of , More convenient . So after the operation ends , You should use close（） Method to close the file , Keep good habits .

Case study ：

Output txt file , Separate use write and QTextStream There are two ways to write .
1. stay .cpp or .h Add header file to

#include <QFile>
#include <QTextStream>

2.cpp The code in the file is as follows , First, construct the file object , Create a file by parameter name , And then to append Way to open a file , Use QTextStream Class to write “ written words ”, Use write（） Function writes a string , Last call close（） Close file .

 	QFile file("Day12.txt");
    file.open(QIODevice::Append);
    // Use QTextStream write file 
    QTextStream tsm(&file);
    QString str = " Please believe that , All accumulation has its specific value ！\r\n";
    tsm<<str<<"Designed by Jack chen";
    file.write("Day12\r\n");
    file.close();

3. Running effect ： Generated under the build directory Day12.txt file , The contents are as follows ：