ASSERT failure in QList<T>::operator[]: "index out of range"

[deleted286]

Read data and appear on the screen every 20 seconds. When i run I have index out of range error.
What my mistake?

#include "mainwindow.h"
#include "ui_mainwindow.h"
#include <QFile>
#include <QTextStream>
#include <QMessageBox>
#include <QTimer>


MainWindow::MainWindow(QWidget *parent)
    : QMainWindow(parent)
    , ui(new Ui::MainWindow)
{
    ui->setupUi(this);

    QTimer *timer = new QTimer(this);

    connect(timer, SIGNAL(timeout()), SLOT(on_pushButton_clicked()));

    QString line = allLines[curIndex];

    ui->plainTextEdit->setPlainText(line);
    if(curIndex < allLines.size() - 1) {
        curIndex++;
    }

timer ->start(20000);



}
MainWindow::~MainWindow()
{
    delete ui;
}


void MainWindow::on_pushButton_2_clicked()  //write
{
    QFile file("C:/Users/ilknu/Documents/QFileDemo/abc.txt");
    if(!file.open(QFile::WriteOnly | QFile::Text )) {

        QMessageBox::warning(this, "title", "file not open");


    }

    QTextStream out (&file);
    QString text = ui->plainTextEdit->toPlainText();
    out << text;
    file.flush();
    file.close();


}

void MainWindow::on_pushButton_clicked()  //read
{

    QFile file("C:/Users/ilknu/Documents/QFileDemo/abc.txt");

    // QMessageBox::warning(this, "title", "file not open");
    // QTextStream in (&file);
    //    while (!in.atEnd()) {
    //        QString text = in.readLine();
    //    }

    //QString text = in.readLine();

  if(file.open(QIODevice::ReadOnly)) {
      QTextStream in (&file);
      while (!in.atEnd()) {

          QString line = in.readLine();
         //  ui -> plainTextEdit->setPlainText(all);

          allLines.append(line); //listeye ekliyoruz


      }


      file.close();  }

  //  file.close();

}

[JonB]

@suslucoder
Your mistake is that you have an index out of range, as the message tells you!

And since the only place you use a QList with an index is:

QString line = allLines[curIndex];

So why don't you debug or print out curIndex on the line above that? At which point, my guess is you discover first time it's an uninitialized member variable...?

[Anonymous_Banned275]

@suslucoder IT may help if you post the actual error message - especially its location .
Another suggestion - when dealing with data - perhaps adding code to tell when the condition is not true may also help.

if( data)
process data.....
else
no data to process