OOP 中的异常（尝试 catch）c++

Question

我需要异常方面的帮助，我想为每个cout 生成异常，我有这个方法，但我有点困惑如何使用每个 if 的 try catch 来生成异常

istream & operator>>(istream & input, Date &date) 
{ 
    int day, mounth, year;
    cout << "please enter day , mounth year" << endl;
    input >> day >> mounth >> year;
    date.setDay(day);
    date.setMonth(mounth);
    date.setYear(year);
    if (day < 1 || day >31)
        throw "Illegal day for month should be number day - between 1 to 31" ;
    if (mounth < 1 || mounth > 12)
        throw "Illegal month should be number mount - between 1 to 12" ;
    if ((mounth == 4 || mounth == 6 || mounth == 9 || mounth == 11)
        && (date.day > 30))
        throw "Illegal day for month " ;
    if (year == 1 && mounth == 1 && day == 1)
        throw "please stop the while loop your date is 1/1/1" ;

        return input;
 }

Answer 1

在您的代码中，既没有 try 也没有 catch 块，throw 关键字需要像这样包装到 try 块中：

try {
    std::cout << "Throwing an integer exception...\n";
    throw 42;
} catch (int i) {
    std::cout << " the integer exception was caught, with value: " << i << '\n';
}

这是来自cppreferencetry catch 页面的示例，我建议您阅读此内容。

根据您的需要，您可以这样做：

int main()
{
    int day = 0;
    try {
        std::cin >> day;
        if (day < 1 || day >31)
            throw std::string("Illegal day for month should be number day - between 1 to 31");
    } catch (const std::string &error) {
        std::cout << "Catch error: " << error << "\n";
    }
}

编写自己的异常处理是一个很好的方法。 这可以帮助您解决这个问题：Creating custom exceptions