EntityManager.md

EntityManager

Provides access to Entities.

Members

Constructor

EntityManager(size_t threads = 0);

An EntityManager can be constructed with a number of threads, which will be used for its ThreadPool.

createEntity

template<typename Func> // Func: void(Entity &);
Entity createEntity(Func && postCreate);

Creates a new Entity, calls postCreate on it, and registers it to the existing Systems.

operator+=

template<typename Func> // Func: void(Entity &)
Entity operator+=(Func && postCreate);

Equivalent to createEntity. Allows for syntax such as:

em += [](Entity & e) {
  e += TransformComponent{};
};

removeEntity

void removeEntity(Entity e);
void removeEntity(Entity::ID id);

getEntity

Entity getEntity(Entity::ID id);

getEntities

auto getEntities();

Returns an iteratable collection over all Entities.

template<typename ...Comps>
auto getEntities<Comps...>();

Returns an iteratable collection over all Entities which have each component listed in Comps.

Dereferencing the iterator returns an std::tuple<Entity, Comps &...>, which means you can write the following:

for (const auto & [e, transform, lua] : em.getEntities<TransformComponent, LuaComponent>()) {
    std::cout << "Pitch: " << transform.pitch << '\n';
    // do stuff
}

no

template<typename T>
struct no;

Can be used as a template parameter for getEntities<Comps...> to filter out Entities which have a specific Component:

for (const auto & [e, transform, noSelected] : em.getEntities<TransformComponent, no<SelectedComponent>>) {
    // Entities with a SelectedComponent will be filtered out
    std::cout << e.id << " has a TransformComponent but no SelectedComponent" << '\n';
}