How to catch out of range array crashed error?

Hi,

After I pressed pushbutton (four times) , variable i is reach 3 (a array is out of range so) application is crashed.
I don't fix this error with checking of array size. I only want to use try .. catch in sample

Code:

---

//header file
 QString a[3];
int i;
 
//cpp file
MainWindow::MainWindow(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::MainWindow)
{
    ui->setupUi(this);
    a[0]="Zero";
    a[1]="Three";
    a[2]="Two";
    i=0;
}
 
MainWindow::~MainWindow()
{
    delete ui;
}
 
void MainWindow::on_pushButton_clicked()
{
    try {
        ui->label->setText(a[i++]);
    }
    catch(std::exception &e){
        qDebug() << "error1" << endl;
    }
    catch (...)
    {
        qDebug() << "error2" << endl;
    }
}

---

Your example code does not throw exceptions, it simply crashes (as you already observed). If you want to experiment with exceptions, replace your

Code:

---

QString a[3];

---

by

Code:

---

#include <vector>
std::vector<QString> a(3); // 3 element vector filled with QString()

---

Next replace the access to the array elements

Code:

---

ui->label->setText(a[i++]);

---

by

Code:

---

ui->label->setText(a.at(i));

---

Note that using operator [] of std::vector does not do any range checking, while at() method will check the range and throw exception std::out_of_range if the index is not inside the vector range. For more details see http://www.cplusplus.com/reference/vector/vector/at/.

Best regards
ars