12.8 MyStringCopyAssignmentOperator.cpp

#include <iostream>
#include <string.h>
using namespace std;

class MyString
{
private:
   char* buffer;
   
public:
   MyString(const char* initialInput)
   {
      if(initialInput != NULL)
      {
         buffer = new char [strlen(initialInput) + 1];
         strcpy(buffer, initialInput);
     }
      else 
         buffer = NULL;
   }

   // Copy assignment operator
   MyString& operator= (const MyString& CopySource)
   {
      if ((this != &CopySource) && (CopySource.buffer != NULL))
      {
         if (buffer != NULL)
          delete[] buffer;

         // ensure deep copy by first allocating own buffer 
         buffer = new char [strlen(CopySource.buffer) + 1];

         // copy from the source into local buffer
         strcpy(buffer, CopySource.buffer);
      }

     return *this;
   }

   operator const char*()
   {
      return buffer;
   }

   ~MyString()
   {
	   delete[] buffer;
   }

   MyString(const MyString& CopySource)
   {
	   cout << "Copy constructor: copying from MyString" << endl;

	   if (CopySource.buffer != NULL)
	   {
		   // ensure deep copy by first allocating own buffer 
		   buffer = new char[strlen(CopySource.buffer) + 1];

		   // copy from the source into local buffer
		   strcpy(buffer, CopySource.buffer);
	   }
	   else
		   buffer = NULL;
   }
};
   
int main()
{
   MyString string1("Hello ");
   MyString string2(" World");

   cout << "Before assignment: " << endl;
   cout << string1 << string2 << endl;
   string2 = string1;
   cout << "After assignment string2 = string1: " << endl;
   cout << string1 << string2 << endl;

   return 0;
}