what is the diffrent between these codes:one of them does'nt change label text

Question

I wrote this code to change label text. but id does not change:

void DateTimes::on_btnHourP_clicked()
{
    int h=ui->txtHour->text().toInt();
    if(h==24)
        h=-1;
    ui->txtHour->setText(QString::number(h++));//*
}

but my label text not change. then I change the code to this:

void DateTimes::on_btnHourP_clicked()
{
    int h=ui->txtHour->text().toInt();
    if(h==24)
        h=-1;
    h+=1;//*
    ui->txtHour->setText(QString::number(h));//*
}  

then the text of my label is change.
why?! could anyone solve my question?

Answer 1

Incremet operator ++ will use the value and then increment. If you want to use the incremented h value within the same expresion. use ++h.

ui->txtHour->setText(QString::number(++h));