Unity ECS：基本组件和功能

// Using typeof to create an EntityArchetype from a set of components
EntityArchetype archetype = EntityManager.CreateArchetype(typeof(MyComponentData), typeof(MySharedComponent));

// Same API but slightly more efficient
EntityArchetype archetype = EntityManager.CreateArchetype(ComponentType.Create<MyComponentData>(), ComponentType.Create<MySharedComponent>());

// Create an Entity from an EntityArchetype
var entity = EntityManager.CreateEntity(archetype);

// Implicitly create an EntityArchetype for convenience
var entity = EntityManager.CreateEntity(typeof(MyComponentData), typeof(MySharedComponent));

// Create an Entity with no components on it
var entity = EntityManager.CreateEntity();

// Adding a component at runtime
EntityManager.AddComponent(entity, new MyComponentData());

// Get the ComponentData
MyComponentData myData = EntityManager.GetComponentData<MyComponentData>(entity);

// Set the ComponentData
EntityManager.SetComponentData(entity, myData);

// Removing a component at runtime
EntityManager.RemoveComponent<MyComponentData>(entity);

// Does the Entity exist and does it have the component?
bool has = EntityManager.HasComponent<MyComponentData>(entity);

// Is the Entity still alive?
bool has = EntityManager.Exists(entity);

// Instantiate the Entity
var instance = EntityManager.Instantiate(entity);

// Destroy the created instance
EntityManager.DestroyEntity(instance);

// EntityManager also provides batch APIs
// to create and destroy many Entities in one call. 
// They are significantly faster 
// and should be used where ever possible
// for performance reasons.

// Instantiate 500 Entities and write the resulting Entity IDs to the instances array
var instances = new NativeArray<Entity>(500, Allocator.Temp);
EntityManager.Instantiate(entity, instances);

// Destroy all 500 entities
EntityManager.DestroyEntity(instances);