virtualcopy.cpp

《24学时精通c++》的光盘内容

 //Listing 17.4 Virtual copy constructor
 #include <iostream>
 
 class Mammal
 {
 public:
     Mammal():itsAge(1) { std::cout << "Mammal constructor...\n"; }
     virtual ~Mammal() { std::cout << "Mammal destructor...\n"; }
     Mammal (const Mammal & rhs);
     virtual void Speak() const { std::cout << "Mammal speak!\n"; }
     virtual Mammal* Clone() { return new Mammal(*this); } 
     int GetAge()const { return itsAge; }
 
 protected:
     int itsAge;
 };
 
 Mammal::Mammal (const Mammal & rhs):itsAge(rhs.GetAge())
 {
     std::cout << "Mammal Copy Constructor...\n";
 }
 
 class Dog : public Mammal
 {
 public:
     Dog() { std::cout << "Dog constructor...\n"; }
     virtual ~Dog() { std::cout << "Dog destructor...\n"; }
     Dog (const Dog & rhs);
     void Speak()const { std::cout << "Woof!\n"; }
     virtual Mammal* Clone() { return new Dog(*this); }
 };
 
 Dog::Dog(const Dog & rhs):
 Mammal(rhs)
 {
     std::cout << "Dog copy constructor...\n";
 }
 
 class Cat : public Mammal
 {
 public:
     Cat() { std::cout << "Cat constructor...\n"; }
     virtual ~Cat() { std::cout << "Cat destructor...\n"; }
     Cat (const Cat &);
     void Speak()const { std::cout << "Meow!\n"; }
     virtual Mammal* Clone() { return new Cat(*this); }
 };
 
 Cat::Cat(const Cat & rhs):
 Mammal(rhs)
 {
     std::cout << "Cat copy constructor...\n";
 }
 
 enum ANIMALS { MAMMAL, DOG, CAT};
 const int NumAnimalTypes = 3;
 int main()
 {
     Mammal *theArray[NumAnimalTypes];
     Mammal* ptr;
     int choice,i;
     for (i = 0; i<NumAnimalTypes; i++)
     {
         std::cout << "(1)dog (2)cat (3)Mammal: ";
         std::cin >> choice;
         switch (choice)
         {
         case DOG: 
             ptr = new Dog;
             break;
         case CAT: 
             ptr = new Cat;
             break;
         default: 
             ptr = new Mammal;
             break;
         }
         theArray[i] = ptr;
     }
     Mammal *OtherArray[NumAnimalTypes];
     for (i=0;i<NumAnimalTypes;i++)
     {
         theArray[i]->Speak();
         OtherArray[i] = theArray[i]->Clone();
     }
     for (i=0;i<NumAnimalTypes;i++)
         OtherArray[i]->Speak();
     return 0;
 }