ECS.hpp - Class enabled Entity/Component System

ECS.hpp is a header-only, class enabled entity/component system which provided a inheritence between different entity classes. Currently, it is in development and is not ready for production use.

Features

1. Native C++ Class support for Entities and Components
2. Entity/Component System

Basic Usage Example

Assuming we have a Node class which has a Position component and a Movable class which inherits from Node and has a Velocity component. We can define the classes as follows:

#include "ECS.hpp"

class Node : public ecs::Entity
{
public:
  ENTITY(Node, ecs::Entity)

  struct Position
  {
    float x, y;
  };
  COMPONENT(Position, position)
};

class Movable : public Node
{
public:
  ENTITY(Movable, Node)  // Inherit from Node

  struct Velocity
  {
    float dx = 1;
    float dy = 1;
  };
  COMPONENT(Velocity, velocity)
};

The ENTITY and COMPONENT macros are used to define the entity and component classes respectively. The first argument to the ENTITY macro is the class name and the second argument is the base class. The COMPONENT macro takes the component name and the member variable name as arguments.

We can now create instances of the Node and Movable classes and access their components as follows:

int main()
{
    Node *a = Node::create();
    Movable *b = Movable::create();

    a->position().x = 10;
    a->position().y = 0;

    b->position().x = 0;
    b->position().y = 10;
    b->velocity().dx = 2;
    b->velocity().dy = 2;
    ...
}

The component macros will create the necessary boilerplate code to access the components of the entities. The create method is used to create instances of the entities.

If you want handle all the entities under a class, you can use the View class to iterate all the entities under the class and its subclasses.

    auto view = ecs::View<Node, Position>();

    // This loop will iterate Node and Movable entities
    for (auto it = view.begin(); it != view.end(); ++it)
    {
        auto [v] = *it;
        v->x = 0;
        v->y = 0;
    }

License

MIT License (c) 2024, sunxfancy