Verification: Is entered - integer number? QT c++

Question

Please help me with optimize the function of checking the entered value. Function returns true and sent value using link, if entered - integer, or returns false if entered char, string(empty). I think there are 2 ways to speed increase: eliminate the use of std::string or eliminate the use of QString.

bool tryRead(int &v)
{
    QString s;
    string s1;
    cin >> s1;
    s = QString::fromStdString(s1);
    if (s.isEmpty())
    {
        cout << "Error! You entered empty string";
        return false;
    }
    bool isNumber = true;
    v = ((s.toInt(&isNumber)));
    if(isNumber == false)
        return false;
    return true;
}

Answer 1

This is what iostream operators are for. A minimal implementation would be:

bool tryRead(int &v){
    cin >> v;
    return cin.good();
}

Depending on what you actually want to accomplish you may want to add some additional sanity checking, error handling and cleanup of cin.

Answer 2

Instead of using cin and cout you can use QTextStream .

QTextStream cin(stdin), cout(stdout);
int myint;
cin >> myint;
if(cin.status() != QTextStream::Ok)
    cout << "It is not an integer!" << endl;

After detecting the error make sure to call QTextStream::resetStatus() to clean the error flags.