QFileDialog::getSaveFileName() returns an empty string after clicking on save in the file dialog

I have this problem when I try to save a file in my GUI with qfiledialog. I don't know why, but as I click on the save_button widget, the file dialog opens, I type in a file name and click save, but my variable saveFileName remains empty after the process, so my program always stops there. I do not click on cancel! I really click on save, so how can getSaveFileName() return an empty string? Thank you!!

void MainWindow::on_save_button_clicked()
{
    QString jsonFilter = "JSON Files (*.json)";
    QString saveFileName = QFileDialog::getSaveFileName(this, "Save file", QDir::homePath(), jsonFilter);

    if(fileName.isEmpty())
    {
        qDebug() << "no save file";
    }
    else
    {
        QJsonDocument jsonSaveDoc;
        QJsonObject jsonSaveObj;   // else statement continues if fileName contains something

You aren't checking the correct variable's value. Maybe it is just a typo, but it should be saveFileName instead of fileName. Try something like this:

void MainWindow::on_save_button_clicked()
{
    QString jsonFilter = "JSON Files (*.json)";
    QString saveFileName = QFileDialog::getSaveFileName(this, "Save file", QDir::homePath(), jsonFilter);

    if(saveFileName.isEmpty())
    {
        qDebug() << "no save file";
    }
    else
    {
        QJsonDocument jsonSaveDoc;
        QJsonObject jsonSaveObj;   // else statement continues if saveFileName contains something
    }
}