Array resize bug in beta build 530 - page 8

[[Deleted]]

angevoyageur:
After fruits (apple, pear), cat, dog and animal. The lack of imagination is terrible when people are talking about oop. (cyclops993, not about you, but wikipedia.) Which real program need a class "animal" with a method "talk". I will post a "trading" example as soon as possible.

Slightly more complete example script:

class Animal {
    public: virtual string talk() {return "";}
};
 
class Cat : public Animal {
    public: string talk() {return "Meow!";}
};
 

class Dog : public Animal {
    public: string talk() {return "Woof!";}
};

void OnStart()
{
   Animal * random;
   if (GetTickCount() % 2 == 0) {
      random = new Cat();
   } else {
      random = new Dog();
   }
   MessageBox(random.talk());  
   delete random;
}

What I hadn't noticed before it is that it doesn't seem to be possible to have virtual functions with no bodies if there is a reference to the base class. In the above example, you can't do the following:

class Animal {
   public: virtual string talk();
};

...whereas in C++ you can do the following:

class Animal {
    public: virtual const char * talk() = 0; // Pure virtual function
};
 
class Cat : public Animal {
    public: const char *  talk() {return "Meow!";}
};
 

class Dog : public Animal {
    public: const char * talk() {return "Woof!";}
};

void main()
{
   Animal * random;
   if (GetTickCount() % 2 == 0) {
      random = new Cat();
   } else {
      random = new Dog();
   }
   printf(random->talk());   
}

[Alain Verleyen]

SDC:

so what would you call class cat and class dog, are they subclasses of animal ? could you create another subclass of dog in the dog class and call it class pitbull ?

Yes it's exactly that. And when using these classes, you use a variable and affects any objects of one class and its subclasses. As shown in the example of cyclops993 (main function), when you call talk() the good function is used.

[Ian Venner]

ok thats kinda neat I think I'm going to make some effort to learn this

[[Deleted]]

SDC:

ok thats kinda neat I think I'm going to make some effort to learn this

For example:

class Pitbull : public Dog {
   public: 
      string talk() {return "Growl!";}
      void menace() {}
};

...Pitbulls can not only talk, like cats and other dogs, but can also menace things.