Demonstrating run-time type id.

   
#include <iostream>
using namespace std;
   
class Mammal {
public:
  virtual bool lays_eggs() { return false; } // Mammal is polymorphic
};
   
class Cat: public Mammal {
public:
};
   
class Platypus: public Mammal {
public:
  bool lays_eggs() { return true; }
};
   
class Dog: public Mammal {
public:
};
   
// A factory for objects derived from Mammal.
Mammal *factory(){
  switch(rand() % 3 ) {
    case 0: return new Dog;
    case 1: return new Cat;
    case 2: return new Platypus;
  }
  return 0;
}
 
int main(){
  Mammal *ptr; // pointer to base class
  int i;
  int c=0, d=0, p=0;
   
  // generate and count objects
  for(i=0; i<10; i++) {
    ptr = factory(); // generate an object
   
    cout << "Object is " << typeid(*ptr).name();
    cout << endl;
   
    // count it
    if(typeid(*ptr) == typeid(Dog)) d++;
    if(typeid(*ptr) == typeid(Cat)) c++;
    if(typeid(*ptr) == typeid(Platypus)) p++;
  }
   
  cout << "  Dogs: " << d << endl;
  cout << "  Cats: " << c << endl;
  cout << "  Platypuses: " << p << endl;
   
  return 0;
}

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Demonstrating run-time type id. : typeid « Development « C++

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