Rename File

[lsropia]

This is simple program, but is not doing the expected...
(Part of the code)

QString ms, fileName;
    QDir dr;
    int dbg;
    QFileInfoList filesList;
    QString ds, qs;
    uint nf;
    int numFiles = filesList.count();
    QUuid uRand = QUuid::createUuid ();
    QUuid uRand2 = QUuid::createUuid ();
 
    for (int ii = 0; ii < numFiles; ii++) {
        fileName = filesList.at(ii).fileName();
        if (dr.rename(fileName, qs.sprintf("%07u", uRand.data1++)))
            out << "Success-I, ii: " << ii << ", fileName: " << fileName << ", uRand.data1: " << uRand.data1 << endl;
        else out << "Fail-I" << endl;
    }
    for (int ii = 0; ii < numFiles; ii++) {
        fileName = filesList.at(ii).fileName();
        if (dr.rename(fileName, qs.sprintf("%07u", uRand2.data1++)))
            out << "Success-II, ii: " << ii << ", fileName: " << fileName << ", uRand.data1: " << uRand2.data1 << endl;
        else out << "Fail-II" << endl;
    }

QString ms, fileName;
    QDir dr;
    int dbg;
    QFileInfoList filesList;
    QString ds, qs;
    uint nf;
    int numFiles = filesList.count();
    QUuid uRand = QUuid::createUuid ();
    QUuid uRand2 = QUuid::createUuid ();

    for (int ii = 0; ii < numFiles; ii++) {
        fileName = filesList.at(ii).fileName();
        if (dr.rename(fileName, qs.sprintf("%07u", uRand.data1++)))
            out << "Success-I, ii: " << ii << ", fileName: " << fileName << ", uRand.data1: " << uRand.data1 << endl;
        else out << "Fail-I" << endl;
    }
    for (int ii = 0; ii < numFiles; ii++) {
        fileName = filesList.at(ii).fileName();
        if (dr.rename(fileName, qs.sprintf("%07u", uRand2.data1++)))
            out << "Success-II, ii: " << ii << ", fileName: " << fileName << ", uRand.data1: " << uRand2.data1 << endl;
        else out << "Fail-II" << endl;
    }

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Output always is:
Success-I, ii: 0, fileName: 915190944, uRand.data1: 815395111
Success-I, ii: 1, fileName: 915190945, uRand.data1: 815395112
Success-I, ii: 2, fileName: 915190946, uRand.data1: 815395113
Success-I, ii: 3, fileName: 915190947, uRand.data1: 815395114
Success-I, ii: 4, fileName: 915190948, uRand.data1: 815395115
Success-I, ii: 5, fileName: 915190949, uRand.data1: 815395116
Success-I, ii: 6, fileName: 915190950, uRand.data1: 815395117
Success-I, ii: 7, fileName: 915190951, uRand.data1: 815395118
Success-I, ii: 8, fileName: 915190952, uRand.data1: 815395119
Success-I, ii: 9, fileName: 915190953, uRand.data1: 815395120
Success-I, ii: 10, fileName: 915190954, uRand.data1: 815395121
Success-I, ii: 11, fileName: 915190955, uRand.data1: 815395122
Fail-II
Fail-II
Fail-II
Fail-II
Fail-II
Fail-II
Fail-II
Fail-II
Fail-II
Fail-II
Fail-II
Fail-II

Why is it not able to rename file second time?

Pls see for yourself, and suggest ways to make it work.

Thanks.