Prototype

Page dedicated to knowledge related to Prototype design pattern described by Robert Nystrom in the game programming patterns..

Note

“object-oriented programming” lets you define “objects” which bundle data and code together.

In my own words

The key idea is that an object can spawn other objects similar to itself.

Basic

// ===== interface defining a spawner =========================================
class Spawner
{
public:
  virtual ~Spawner() {}
  virtual Monster* spawnMonster() = 0;
};
// ===== template class to spawn class of type T ==============================
template <class T>
class SpawnerFor : public Spawner
{
public:
  virtual Monster* spawnMonster() { return new T(); }
};
// ===== spawn a ghost class ==================================================
Spawner* ghostSpawner = new SpawnerFor<Ghost>();

Later on, we can use some JSON format to spawn class with specific values for attributes. The constructor or the spawner can have default values that can be overriden.

{
  "name": "goblin grunt",
  "minHealth": 20,
  "maxHealth": 30,
  "resists": ["cold", "poison"],
  "weaknesses": ["fire", "light"]
}

{
  "name": "goblin wizard",
  "prototype": "goblin grunt",
  "spells": ["fire ball", "lightning bolt"]
}

{
  "name": "goblin archer",
  "prototype": "goblin grunt",
  "attacks": ["short bow"]
}