I must replace the QRegExp with QRegularExpression, and I had the check for “a string contains only white space characters” working, but I don’t know how to set QRegularExpression to do the same thing. Here is a sample code (in comments, I put the result – and the desired result).

#include <QCoreApplication>
#include <QDebug>
#include <QRegExp>
#include <QRegularExpression>

int main(int argc, char *argv[])
{
    QCoreApplication a(argc, argv);

    QString inputString1 = "thisisatest";
    QString inputString2 = "this is a test";
    QString inputString3 = " nt";

    // How do I make this work the same as QRegExp ?
    QRegularExpression whiteSpace(QStringLiteral("\s*"));
    qDebug() << whiteSpace.match(inputString1).hasMatch();  // Weird !!! says true. Should be false
    qDebug() << whiteSpace.match(inputString2).hasMatch();  // Says true. Should be false
    qDebug() << whiteSpace.match(inputString3).hasMatch();  // I only want this to be true

    // This is the old behavior that I want to keep
    QRegExp whiteSpace1(QStringLiteral("\s*"));
    qDebug() << whiteSpace1.exactMatch(inputString1);       // False
    qDebug() << whiteSpace1.exactMatch(inputString2);       // False
    qDebug() << whiteSpace1.exactMatch(inputString3);       // True

    return 0;
}