entity - is stable int16 identifier used as index. 0 index used as invalid null-entity. passport - is mix of entity index and cyclic version number (generation) to store and invalidate logical references to entity. component_type - is data manager which control association of entity with some logical component and it's data. component_handle - is index used to access component's data arrays.

Lifecycle

• user initialize ecs system
• user creates new entity (no on_entity_created callback)
• add new component to entity: component type ctor is called.
• remove component from entity: component type dtor is called.
• user destroy entity
  • system clears entity from all components
  • on_entity_destroy callbacks fired
• user shutdown ecs system
  • system destroys all component data (dtor calls for each created data)
  • call shutdown callback for each component type, here user should terminate temporary communication managers between ecs components and external systems.
• user shutdown external systems