Virtual Copy Constructor Help

[incognito]

//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())
/*Could you please tell me what this constructor here does.. the extra ":" is confusing me */
{
	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();
  int x;
  cin>>x;

	return 0;

}

/*Could you please tell me what the last two for loops do exactly because I am a bit confused......Thank you in advance */

[Stoned_Coder]

Mammal::Mammal (const Mammal & rhs):itsAge(rhs.GetAge())
/*Could you please tell me what this constructor here does.. the extra ":" is confusing me */
{
cout << "Mammal Copy Constructor...\n";
}

This is a copy constructor.This constructs a mammal object from another mammal object. The extra : that is putting you off is an initialization list. It is very similar to ....

Mammal::Mammal (const Mammal & rhs)
/*Could you please tell me what this constructor here does.. the extra ":" is confusing me */
{
itsAge=rhs.GetAge();	
cout << "Mammal Copy Constructor...\n";
}

/*Could you please tell me what the last two for loops do exactly because I am a bit confused......Thank you in advance */

The first loop fills an array with pointers to dynamically created mammal objects (or derived from mammal objects).
The second loop shows polymorphic calls to the objects member functions.
The third loop shows polymorphic calls to the objects member functions.
Run the program and note the output. What do you think is happening? Which functions get called and why?

[incognito]

Ok, so when you call a Mammal Clone constructor a copy of the constructor is sent....or am I wrong? Why are all of the Mammal clone constructors, and the Dog's and, etc, all declared to be virtual, I thought you only declared one of them the base method/or constructor virtual if you wanted to overload them.

[Stoned_Coder]

none of the constructors are virtual. The function clone() is. Its job is to call a copy constructor. It will create a copy of whatever type of object it is called through.It is virtual so that when working in terms of Mammal* pointers the right function for the object gets called.