c++ - 无法创建两个继承自 std::logic_error 的自定义异常类

Question

我的 cs 类任务是创建两个继承自 std::logic_error 的自定义异常类:OverflowingSwimmingPoolException 和 UnderflowingSwimmingPoolException。当尝试进行非法操作时，创建并抛出自定义异常，而不仅仅是打印错误消息。在您的驱动程序代码中包含 try...catch block 以捕获任何异常。

这是我的头文件的一部分:

    #ifndef SWIMMINGPOOL_H
    #define SWIMMINGPOOL_H
    #include <stdexcept>
    #include <iostream>
    using namespace std;



 namespace cs52
  {
          class OverflowingSwimmingPoolException: public logic_error
  {

    OverflowingSwimmingPoolException (){};

};

class UnderflowingSwimmingPoolException: public logic_error
{

    UnderflowingSwimmingPoolException(){};
};

这是编译器在构造函数所在的行中说的:“cs52::UnderflowingSwimmingPoolException”的构造函数必须显式初始化没有默认构造函数的基类“std::logic_error”。

这就是我的实现文件中的内容:

    #include "SwimmingPool.h"
    #include <stdexcept>
    #include <iostream>
     using namespace std;



     namespace cs52
     {       
      SwimmingPool operator +(const SwimmingPool& pool1, const SwimmingPool&         pool2) throw (OverflowingSwimmingPoolException, UnderflowingSwimmingPoolException)
{
    SwimmingPool temp;
    temp.mySize = pool1.mySize+pool2.mySize;
    temp.myContents = pool1.myContents+pool2.myContents;
    if (temp.myContents>temp.mySize)
   throw OverflowingSwimmingPoolException();
    return temp;
}
SwimmingPool operator -(const SwimmingPool& pool1, const SwimmingPool& pool2) throw (OverflowingSwimmingPoolException, UnderflowingSwimmingPoolException)
{
    SwimmingPool temp;
    temp.mySize= pool1.mySize-pool2.mySize;
    temp.myContents= pool1.myContents-pool2.myContents;
    if (temp.myContents>temp.mySize)
        throw OverflowingSwimmingPoolException();
    if (temp.myContents<0 || temp.mySize<0)
        throw UnderflowingSwimmingPoolException();
    return temp;
}
}

编译器在我抛出异常类的行中显示错误。它说:调用 cs53 类的私有(private)构造函数:OverflowingSwimmimgPoolException。

我的驱动程序文件的一部分应该看起来像这样:

   using namespace cs52;
   try {
    SwimmingPool badPool = smallOne - bigOne;
    cout << "This should never happen..." << endl;
    } 
    catch( UnderflowingSwimmingPoolException uspe ) {
    cout << "working..." << endl;
    } 
    catch( OverflowingSwimmingPoolException uspe ) {
    cout << "This should never happen..." << endl;
    }

我刚刚开始编写代码，所以我不太了解库中已经创建的类(如 std::logic_error)是如何工作的。

Answer 1

错误很明显，与逻辑无关，也与您抛出异常的时间、地点和方式无关。这只是关于异常类本身和构造函数。

注意错误是怎么说你必须初始化父类的？您可以使用构造函数初始化列表来做到这一点，例如

OverflowingSwimmingPoolException ()
    : std::logic_error("Some error message")
{}

std::logic_error 初始化中的错误信息是what函数将报告。