QT里endl无法识别以下是问题代码的头文件和代码部分求解答

```c++

#include "mainwindow.h"

#include "ui_mainwindow.h"

#include

#include

#include

void MainWindow::on_pushButton_clicked()

{

QFile initial_D("C://Users//19878//Desktop//demo2.0//untitled//example.txt"); //创建文件存放的路径

if(!initial_D.open(QIODevice::Append|QIODevice::Text)){

qDebug()<<"Error opening file";

return;

}

// initial_D.open(QIODevice::Append|QIODevice::Text);//Append可以连续的输入内容而不被覆盖

QTextStream in(&initial_D);

using namespace std;

in <<"hello world"<

initial_D.close();//关闭文件

}

```