ex9_05.cpp

Beginning Visual C++ 6源码。Wrox。

// EX9_05.CPP
// Overloaded copy operator perfection
#include <iostream>
#include <cstring>
using namespace std;

class CMessage
{
   private:
      char* pmessage;                     // Pointer to object text string

   public:
      // Function to display a message
      void ShowIt() const
      {
         cout << endl << pmessage;
      }

      //Function to reset a message to *
      void Reset()
      {
         char* temp = pmessage;
         while(*temp)
            *(temp++) = '*';
      }

      // Overloaded assignment operator for CMessage objects
      CMessage& operator=(const CMessage& aMess)
      {
         if(this == &aMess)               // Check addresses, if equal
            return *this;                 // return the 1st operand

         // Release memory for 1st operand
         delete[] pmessage;
         pmessage = new char[ strlen(aMess.pmessage) +1];

         // Copy 2nd operand string to 1st
         strcpy(this->pmessage, aMess.pmessage);

         // Return a reference to 1st operand
         return *this;
      }

      // Constructor definition
      CMessage(const char* text = "Default message")
      {
         pmessage = new char[ strlen(text) +1 ]; // Allocate space for text
         strcpy(pmessage, text);                 // Copy text to new memory
      }

      // Destructor to free memory allocated by new
      ~CMessage()
      {
         cout << "Destructor called."     // Just to track what happens
              << endl;
         delete[] pmessage;               // Free memory assigned to pointer
      }
};

int main()
{
   CMessage motto1("The devil takes care of his own");
   CMessage motto2;

   cout << "motto2 contains - ";
   motto2.ShowIt();
   cout << endl;

   motto2 = motto1;                       // Use new assignment operator

   cout << "motto2 contains - ";
   motto2.ShowIt();
   cout << endl;

   motto1.Reset();                        // Setting motto1 to * doesn't
                                          // affect motto2

   cout << "motto1 now contains - ";
   motto1.ShowIt();
   cout << endl;

   cout << "motto2 still contains - ";
   motto2.ShowIt();
   cout << endl;

   return 0;
}