类异常和运算符

Question

我在让很多操作员工作时遇到了一些麻烦

作业说明如下

本任务的目的是处理例外情况。您可能还记得，我为您提供了一个名为FlashDrive的示例类，如下图所示。您可以在此处获取FlashDrive类的源（.NET或.NET 2010）。我希望您增强该类，以便调用其方法或运算符可能引发异常，而不仅仅是将错误消息打印到cout。目前，我们最喜欢的异常类是std:：logic\u error。您可以通过向其构造函数传递字符串值来创建逻辑错误。正式来说，你也应该说#include开始处理逻辑错误，但是visualstudio（作为一个行为不好的孩子…）让我们不带它就走吧。一旦一切正常运行，驱动程序代码应该按照类中的描述运行。

虽然示例驱动程序代码可能不适用于所有这些情况，但我希望您在以下情况下抛出异常：

驱动器上放的东西超过了它的安全容量（由于writeData）

一个负数可能用作my_StorageUsed值（由于运算符–或发送给构造函数调用的坏值）

负数可能用作my_StorageCapacity值（由于运算符–或发送给构造函数调用的坏值），因此请小心地遍历类的所有运算符和方法，以确保在每种情况下都抛出逻辑_错误。

我还想请你们接接线员

下面是我的代码和构建输出

FlashDrive。H

#ifndef FLASHDRIVE_H
#define FLASHDRIVE_H
#include <iostream>
#include <cstdlib>

namespace cs52 {

class FlashDrive {
    friend FlashDrive operator+ (FlashDrive used1 , FlashDrive used2);
    friend FlashDrive operator- (FlashDrive used3, FlashDrive used4 );

public:

    FlashDrive& FlashDrive::operator=(int);
    FlashDrive::FlashDrive(int);
    FlashDrive& operator = (const FlashDrive& usedtotal){
        my_StorageUsed= usedtotal.my_StorageUsed;
        return *this;
    }
    FlashDrive( );
    FlashDrive( int capacity, int used, bool pluggedIn );

    void plugIn( );
    void pullOut( );
    void writeData( int amount );
    void eraseData( int amount );
    void formatDrive( );

    int  getCapacity( );
    void setCapacity( int amount );
    int  getUsed( );
    void setUsed( int amount );
    bool isPluggedIn( );

private:
    int my_StorageCapacity;   // in kilobytes
    int my_StorageUsed;       // in kilobytes
    bool my_IsPluggedIn;      // am I attached to a computer?
}extern drive1,drive2;

inline FlashDrive operator+ (FlashDrive used1, FlashDrive used2 ) {

    FlashDrive plus;

    plus.my_StorageUsed = (used1.getUsed()+ used2.getUsed());
    return plus;
}
inline bool operator< (FlashDrive &lhs,FlashDrive &rhs ) {
   return ( lhs.getUsed() < rhs.getUsed() );
}
inline bool operator> (FlashDrive &lhs,FlashDrive &rhs ) {
   return ( operator <( rhs, lhs ) );
}
inline FlashDrive operator - (FlashDrive used3, FlashDrive used4 ){
    FlashDrive minus;
    minus.my_StorageUsed = (used3.getUsed()- used4.getUsed());
    return minus;
};

}
#endif 

FlashDrive。cpp

#include <iostream>
#include <cstdlib>
#include "FlashDrive.h"

namespace cs52 {

FlashDrive::FlashDrive( ) {
  my_StorageCapacity = 0;
  my_StorageUsed = 0;
  my_IsPluggedIn = false;
}
FlashDrive::FlashDrive( int capacity, int used, bool pluggedIn ) { 
  my_StorageCapacity = capacity;
  my_StorageUsed = used;
  my_IsPluggedIn = pluggedIn;
}
void FlashDrive::plugIn( ) {
  my_IsPluggedIn = true;
}
void FlashDrive::pullOut( ) {
  my_IsPluggedIn = false;
}
void FlashDrive::writeData( int amount ) {
  my_StorageUsed += amount;
}
void FlashDrive::eraseData( int amount ) {
  my_StorageUsed -= amount;
}
void FlashDrive::formatDrive( ) {
  my_StorageUsed = 0;
}

int  FlashDrive::getCapacity( ) {
  return( my_StorageCapacity );
}
void FlashDrive::setCapacity( int amount ) {
  my_StorageCapacity = amount;
}
int  FlashDrive::getUsed( ) {
  return( my_StorageUsed );
}
void FlashDrive::setUsed( int amount ) {
  my_StorageUsed = amount;
}
bool FlashDrive::isPluggedIn( ) {
  return( my_IsPluggedIn );
}
}

主要的cpp

#include <iostream>
#include <cstdlib>
#include "FlashDrive.h"
void main( )
{
using namespace cs52;
cs52::FlashDrive empty;
cs52::FlashDrive drive1( 10, 0, false );
cs52::FlashDrive drive2( 20, 0, false );

drive1.plugIn( );
drive1.formatDrive( );
drive1.writeData( 5 );
drive1.pullOut( );

drive2.plugIn( );
drive2.formatDrive( );
drive2.writeData( 1 );
drive2.pullOut( );

// read in a FlashDrive... 
// the class designer for FlashDrive (that's you!)
// gets to decide which fields matter and should be read in
cs52::FlashDrive sample;
cin >> sample;

// print out a FlashDrive...
// the class designer for FlashDrive (that's you!)
// gets to decide which fields matter and should be printed
cout << sample << endl;

cs52::FlashDrive combined = drive1 + drive2;
cout << "this drive's filled to " << combined.getUsed( ) << endl;

cs52::FlashDrive other = combined – drive1;
cout << "the other cup's filled to " << other.getUsed( ) << endl;

if (combined > other) {
  cout << "looks like combined is bigger..." << endl;
}
else {
  cout << "looks like other is bigger..." << endl;
}

if (drive2 > other) {
  cout << "looks like drive2 is bigger..." << endl;
}
else {
  cout << "looks like other is bigger..." << endl;
}

if (drive2 < drive1) {
  cout << "looks like drive2 is smaller..." << endl;
}
else {
  cout << "looks like drive1 is smaller..." << endl;
}

// let's throw some exceptions...

try {
  empty = empty - combined;
  cout << "something not right here..." << endl;
} catch( std::logic_error ) {
// an exception should get thrown... 
// so the lines of code here should
// be run, not the cout statement...
}

try {
  drive2.writeData( 10000 );
  cout << "something not right here..." << endl;
} catch( std::logic_error ) {
// an exception should get thrown... 
// so the lines of code here should
// be run, not the cout statement...
}

try {
  cs52::FlashDrive f( -1, -1, false );
  cout << "something not right here..." << endl;
} catch( std::logic_error ) {
// an exception should get thrown... 
// so the lines of code here should
// be run, not the cout statement...
}
}

这是一个非常奇怪的错误信息

------构建开始：项目：FlashDriver，配置：调试Win32------构建开始于2013年7月29日上午4:48:43。InitializeBuildStatus：触摸“调试\ FlashDriver.unsuccessfulbuild”。ClCompile:Main。cpp c:\documents and settings\administrator\my documents\visual studio 2010\projects\flashdriver\flashdriver\main。cpp（28）：错误C2678:二进制'

生成失败。

时间流逝00:00:01.82 ========== 构建：0成功，1失败，0最新，0跳过 ==========

Answer 1

您需要定义运算符

friend std::istream& operator>>(std::istream& is, FlashDrive& fd)
{
  is >> my_StorageCapacity >> my_StorageUsed >> my_IsPluggedIn;
  return is;
}

类似地，您可以定义运算符

std::ostream& operator>>(std::ostream& os, const FlashDrive& fd)
{
  os << fd.getCapacity() << fd.getUsed() << fd.isPluggedIn();
  return os;
}