Convert Qstring using QList to double

Question

I want to convert the Qstring in the QLineEdit to double using QList so that it could perform a calculation and display the results in the QMessagebox. If I can get some suggestions on how this can be done it would be great.

#include <QtGui>
#include <QList>

#include <iostream>

int main (int argc, char* argv[])
{
    QApplication app(argc, argv);
    QTextStream cout(stdout);

    bool ok;
    double answer;

    do
    {
        QString mark =  QInputDialog::getText(NULL ,"MarkCalc","Enter Mark:", QLineEdit::Normal,"", &ok);

        if (ok && !mark.isEmpty())    
             QList <QString> list;

        double am = (mark * 0.20)+(mark * 0.50)+(mark * 0.30);
        double ym = am * 0.20;
        double em = 75 * 0.40;
        double fm = em + ym;

        if (em <= 40 && fm >= 50)
            cout <<"pass";
        else
            cout << "fail";

        QString response = QString("Your Final Mark: %1 \n\n%5").arg(ym).arg(em);
        answer = QMessageBox::question(0, "Final Marks", response,QMessageBox::Yes | QMessageBox::No);
    } while (answer == QMessageBox::Yes);

    return 0;
}

Answer 1

Here is an example taking the code from the OP and splitting the QString to a QStringList then using foreach to iterate over the list converting each QString in the list to a double then printing the double using cout:

#include <QtGui>
#include <QtCore>
#include <QtWidgets>


int main (int argc, char* argv[]) {
    QApplication app(argc, argv);
    QTextStream cout(stdout);

    bool ok;
    double answer;

    do{

        QString mark =  QInputDialog::getText(NULL ,"MarkCalc","Enter Mark:", QLineEdit::Normal,"", &ok);

        if (ok && !mark.isEmpty()) {

            QStringList list = mark.split(",");

            foreach(QString str, list) {
                double d = str.toDouble();
                cout << d << endl;
            }


//            double am = (mark * 0.20)+(mark * 0.50)+(mark * 0.30);
//            double ym = am * 0.20;
//            double em = 75 * 0.40;
//            double fm = em + ym;
//            if (em <= 40 && fm >= 50)
//                cout <<"pass";
//            else
//                cout << "fail";


//            QString response = QString("Your Final Mark: %1 \n\n%5").arg(ym).arg(em);
//            answer = QMessageBox::question(0, "Final Marks", response,QMessageBox::Yes | QMessageBox::No);
        }
    } while (answer == QMessageBox::Yes);


    return 0;
}

The following line splits the QString into a QStringList using a comma for the split.

QStringList list = mark.split(",");

After that I use a foreach to iterate over the QStringList one string at a time converting each string to a double and outputting the double one line for each double:

foreach(QString str, list) {
    double d = str.toDouble();
    cout << d << endl;
}