获取comboBox里面的item使用的方法

使用currentIndex()或者currentText()

void Widget::calc()
{
    int first = ui->firstLineEdit->text().toInt();
    int second = ui->secondLineEdit->text().toInt();
    int result;
    switch(ui->comboBox->currentIndex())
    {
    case 0:
        result = first + second;
        ui->resultLineEdit->setText(QString::number(result));
        break;
    case 1:
        result = first - second;
        ui->resultLineEdit->setText(QString::number(result));
        break;
    case 2:
        result = first * second;
        ui->resultLineEdit->setText(QString::number(result));
        break;
    case 3:
        if(second != 0)
        {
            result = first / second;
            ui->resultLineEdit->setText(QString::number(result));
        }
        break;
    default:break;
    }
}