When to Use Public Inheritance

Public inheritance is appropriate when there is an "is-a" relationship between the derived class and the base class.

For example, consider a game with a Character base class and derived classes representing player characters and non-player characters (NPCs).

We can say a Player "is a" Character, and an NPC "is a" Character. They share common attributes and behaviors that can be inherited from Character.

1class Character {
2public:
3  void Move() {/*...*/ }
4protected:
5  int health_;
6};
7
8class Player : public Character {
9public:
10  void SpecialAbility() {/*...*/ }
11};
12
13class NPC : public Character {
14public:
15  void Dialogue() {/*...*/ }
16};

Here, Player and NPC inherit the Move() function and health_ member from Character, but also add their own unique functionality.

Public inheritance allows us to treat derived objects as if they were base objects. For example, we could have a std::vector<Character*> that stores pointers to both Player and NPC objects.

Use public inheritance when:

• The derived class "is a" specialization of the base
• You want the base class interface to be available to users of the derived class
• You want to be able to use derived objects in place of base objects