C++虚复制构造函数

构造函数不能是虚函数。但有时候确实需要能传递一个指向基类对象的指针，并且有已创建的派生类对象的拷贝。通常在类内部创建一个Clone()方法，并设置为虚函数。

//Listing 12.11 Virtual copy constructor

#include <iostream>

using namespace std;

class Mammal

{

  public:

     Mammal():itsAge(1) { cout << "Mammal constructor...\n"; }

     virtual ~Mammal() { cout << "Mammal destructor...\n"; }

     Mammal (const Mammal & rhs);

     virtual void Speak() const { 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())

{

   cout << "Mammal Copy Constructor...\n";

}
class Dog : public Mammal

{

  public:

    Dog() { cout << "Dog constructor...\n"; }

    virtual ~Dog() { cout << "Dog destructor...\n"; }

    Dog (const Dog & rhs);

    void Speak()const { cout << "Woof!\n"; }

    virtual Mammal* Clone() { return new Dog(*this); }

};
Dog::Dog(const Dog & rhs):

Mammal(rhs)

{

   cout << "Dog copy constructor...\n";

}
class Cat : public Mammal

{

  public:

    Cat() { cout << "Cat constructor...\n"; }

    ~Cat() { cout << "Cat destructor...\n"; }

    Cat (const Cat &);

    void Speak()const { cout << "Meow!\n"; }

    virtual Mammal* Clone() { return new Cat(*this); }

};
Cat::Cat(const Cat & rhs):

Mammal(rhs)

{

   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++)

   {

      cout << "(1)dog (2)cat (3)Mammal: ";

      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;

}

输出结果：

(1)dog (2)cat (3)Mammal: 3
Mammal
constructor...
Woof!
Mammal Copy
Constructor...
Dog copy
constructor...
Meow!
Mammal Copy Constructor...
Cat copy
constructor...
Mammal speak!
Mammal Copy
Constructor...
Woof!
Meow!
Mammal speak!

C++虚复制构造函数,码迷,mamicode.com