list1209.cpp

teach yourself C++ in 21 days 第五版

//Listing 12.9 Multiple virtual functions called in turn
#include <iostream>
using namespace std;

class Mammal
{
  public:
     Mammal():itsAge(1) {  }
     virtual ~Mammal() { }
     virtual void Speak() const { cout << "Mammal speak!\n"; }
  
  protected:
     int itsAge;
};

class Dog : public Mammal
{
  public:
    void Speak()const { cout << "Woof!\n"; }
};

class Cat : public Mammal
{
  public:
    void Speak()const { cout << "Meow!\n"; }
};


class Horse : public Mammal
{
  public:
    void Speak()const { cout << "Winnie!\n"; }
};

class Pig : public Mammal
{
  public:
    void Speak()const { cout << "Oink!\n"; }
};

int main()
{
   Mammal* theArray[5];
   Mammal* ptr;
   int choice, i;
   for ( i = 0; i<5; i++)
   {
      cout << "(1)dog (2)cat (3)horse (4)pig: ";
      cin >> choice;
      switch (choice)
      {
        case 1: ptr = new Dog;
                break;
        case 2: ptr = new Cat;
                break;
        case 3: ptr = new Horse;
                break;
        case 4: ptr = new Pig;
                break;
        default: ptr = new Mammal;
                 break;
      }
      theArray[i] = ptr;
   }
   for (i=0;i<5;i++)
      theArray[i]->Speak();
   return 0;
}