Entitas++ is a fast Entity Component System Framework (ECS) C++11 port of Entitas v0.29.0 for C# and Unity.
There are some differences between both, so please check the code and notes below !
Any feedback is welcome !
As in Entitas C#, basic code architecture is the same:
+------------------+
| Pool |
|------------------|
| e e | +-----------+
| e e---|----> | Entity |
| e e | |-----------|
| e e e | | Component |
| e e | | | +-----------+
| e e | | Component-|----> | Component |
| e e e | | | |-----------|
| e e e | | Component | | Data |
+------------------+ +-----------+ +-----------+
|
|
| +-------------+ Groups:
| | e | Subsets of entities in the pool
| | e e | for blazing fast querying
+---> | +------------+
| e | | |
| e | e | e |
+--------|----+ e |
| e |
| e e |
+------------+
public class PositionComponent : IComponent {
public float x;
public float y;
public float z;
}
//...
var pool = new Pool(ComponentIds.TotalComponents);
var e = pool.CreateEntity();
e.AddPosition(1f, 2f, 3f);
e.ReplacePosition(3f, 2f, 1f);
e.RemovePosition();
var posX = e.position.x;
var hasPosition = e.hasPosition;// I suggest you to use structs instead, they are the same and all members/methods are public by default.
class Position : public IComponent {
public:
// You must provide at least ONE public "Reset" method with any parameters you want
void Reset(float px, float py, float pz) {
x = px;
y = py;
z = pz;
}
float x;
float y;
float z;
};
//...
auto pool = new Pool();
auto e = pool->CreateEntity();
e->Add<Position>(1f, 2f, 3f);
e->Replace<Position>(3f, 2f, 1f);
e->Remove<Position>();
float posX = e->Get<Position>()->x;
bool hasPosition = e->Has<Position>();entity.AddPosition(3, 7);
entity.AddHealth(100);
entity.isMovable = true;
entity.ReplacePosition(10, 100);
entity.ReplaceHealth(entity.health.value - 1);
entity.isMovable = false;
entity.RemovePosition();
var hasPos = entity.hasPosition;
var movable = entity.isMovable;entity->Add<Position>(3, 7);
entity->Add<Health>(100);
entity->Replace<Movable>(); // There is no helper in here, you must use "Replace" and "Remove" methods
entity->Replace<Position>(10, 100);
entity->Replace<Health>(entity->Get<Health>()->value - 1);
entity->Remove<Movable>();
entity->Remove<Position>();
bool hasPos = entity->Has<Position>();
bool movable = entity->Has<Movable>(); // Again, you must use "Has" to check if an entity has a component// Pools.pool is kindly generated for you by the code generator
var pool = Pools.pool;
var entity = pool.CreateEntity();
entity.isMovable = true;
// Returns all entities having MovableComponent and PositionComponent.
// Matchers are also generated for you.
var entities = pool.GetEntities(Matcher.AllOf(Matcher.Movable, Matcher.Position));
foreach (var e in entities) {
// do something
}// No code generator == no "Pools". You must handle yourself your Pools !
auto pool = new Pool();
auto entity = pool->CreateEntity();
entity->Replace<Movable>(); // I used "Replace" but in this case is better to use "Add" directly
// Returns all entities having MovableComponent and PositionComponent.
// Matchers are also generated for you.
auto entities = pool->GetEntities(Matcher_AllOf(Movable, Position)); // *Some magic preprocessor involved*
for (auto &e : entities) { // e is a shared_ptr of Entity
// do something
}pool.GetGroup(Matcher.Position).OnEntityAdded += (group, entity, index, component) => {
// Do something
};pool->GetGroup(Matcher_AllOf(Position))->OnEntityAdded += [](std::shared_ptr<Group> group, EntityPtr entity, ComponentId index, IComponent* component) {
// Do something
};var group = pool.GetGroup(Matcher.Position);
var observer = group.CreateObserver(GroupEventType.OnEntityAdded);
foreach (var e in observer.collectedEntities) {
// do something
}
observer.ClearCollectedEntities();auto group = pool->GetGroup(Matcher_AllOf(Position)); // There are _AnyOf and _NoneOf too !
auto observer = group->CreateObserver(GroupEventType::OnEntityAdded);
for (auto &e : observer->GetCollectedEntities()) {
// do something
}
observer->ClearCollectedEntities();public class MoveSystem : IExecuteSystem, ISetPool {
Group _group;
public void SetPool(Pool pool) {
_group = pool.GetGroup(Matcher.AllOf(Matcher.Move, Matcher.Position));
}
public void Execute() {
foreach (var e in _group.GetEntities()) {
var move = e.move;
var pos = e.position;
e.ReplacePosition(pos.x, pos.y + move.speed, pos.z);
}
}
}class MoveSystem : public IExecuteSystem, public ISetPool {
std::weak_ptr<Group> _group;
public:
void SetPool(Pool* pool) {
_group = pool->GetGroup(Matcher_AllOf(Move, Position));
}
void Execute() {
for (auto &e : _group.lock()->GetEntities()) {
auto move = e->Get<Move>();
auto pos = e->Get<Position>();
e->Replace<Position>(pos->x, pos->y + move->speed, pos->z);
}
}
};public class RenderPositionSystem : IReactiveSystem {
public TriggerOnEvent trigger { get { return Matcher.AllOf(Matcher.Position, Matcher.View).OnEntityAdded(); } }
public void Execute(List<Entity> entities) {
// Gets executed only if the observed group changed.
// Changed entities are passed as an argument
foreach (var e in entities) {
var pos = e.position;
e.view.gameObject.transform.position = new Vector3(pos.x, pos.y, pos.z);
}
}
}class RenderPositionSystem : public IReactiveSystem {
public:
RenderPositionSystem() {
trigger = Matcher_AllOf(Position, View).OnEntityAdded();
}
void Execute(std::vector<EntityPtr> entities) {
// Gets executed only if the observed group changed.
// Changed entities are passed as an argument
for (auto &e : entities) {
auto pos = e->Get<Position>();
// NOTE: Unity-only example, but this maybe could be the code if Unity were compatible with C++
e->Get<View>()->gameObject.transform.position = new Vector3(pos->x, pos->y, pos->z);
}
}
}- All code above was written using:
using namespace EntitasPP;, if you don't, you must prepend all the classes with the namespaceEntitasPP::. - There is no code generator because C++ lacks of code reflection. So all code must be done by you, but there are a lot of templating involved in here to ease the work for you anyways (see code above).
- 'Systems' class was renamed to 'SystemContainer'. You can see a simple example of use in the provided 'main.cpp'.
- All 'ToString()' methods were removed. If you need to track identifiers between entities I suggest you to use your own custom Component.
- AERC (Automatic Entity Reference Counting) was implemented using smart pointers. (Yeah! Take that C# 😜)
If you need more documentation of the architecture of the framework, please go to Entitas v0.29.0 C# Wiki since this framework has a lot on common with the original C# one.
Copyright © 2020 Juan Delgado (JuDelCo)
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