博客

1）例子1

try

{


   int a=5/0;


}


catch(…)


{


   printf(“catch the exception!”);

}

2）例子2

void Widget::check()
{    
if(le->text()==””)
{
throw QString(“Please input a positive number!”);             //抛出異常信息
//        throw 1;                                                        
}
else
{
if(a<0)
{
throw QString(“Do input a positive number!”);                   //抛出異常信息
//            throw 2;
}        
}

}
void Widget::compute()
{
try                                                         //定義異常
{
a = le->text().toInt();
check();                                                 //調用函數，確保異常被提前抛出
label->clear();
double root = sqrt(a);                            //關鍵位置，容易出錯的地方。
QString res = QString::number(root);
label->setText(res);
}
catch(QString exception)                      //定義異常處理，可以抓取多種類型的異常信息
//    catch(int errorcode)
{
QMessageBox::about(this,”Error”,exception);
//        QMessageBox::about(this,”Error”,QString::number(errorcode));
}
}

Widget::~Widget()
{
}
/

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在上面的异常处理中，我们可以看到，throw可以带参数(可以是int,也可以使QString)，也可以不带参数（对应的catch(…)).

当然,一定要记住,try{}catch(){}一定要异常定义得正确,不然,都已经throw出去了,还没到catch…就会报错说:

Qt has caught an exception thrown from an event handler. Throwing
exceptions from an event handler is not supported in Qt. You must
reimplement QApplication::notify() and catch all exceptions there.