Constraint Traits

Traits that enforce constraints on entities, components and relationships. More...

Collaboration diagram for Constraint Traits:

Variables
FLECS_API const ecs_entity_t	EcsFinal
	Ensure that an entity or component cannot be used as a target in an IsA relationship.
FLECS_API const ecs_entity_t	EcsSymmetric
	Mark relationship as commutative.
FLECS_API const ecs_entity_t	EcsAcyclic
	Mark a relationship as acyclic.
FLECS_API const ecs_entity_t	EcsOneOf
	Ensure that a relationship target is a child of the specified entity.
FLECS_API const ecs_entity_t	EcsTrait
	Can be added to components to indicate it is a trait.
FLECS_API const ecs_entity_t	EcsRelationship
	Ensure that an entity is always used in a pair as a relationship.
FLECS_API const ecs_entity_t	EcsTarget
	Ensure that an entity is always used in a pair as a target.
FLECS_API const ecs_entity_t	EcsSingleton
	Mark component as singleton.

Detailed Description

Traits that enforce constraints on entities, components and relationships.

Variable Documentation

EcsAcyclic

FLECS_API const ecs_entity_t EcsAcyclic

extern

Mark a relationship as acyclic.

Acyclic relationships may not form cycles.

EcsFinal

FLECS_API const ecs_entity_t EcsFinal

extern

Ensure that an entity or component cannot be used as a target in an IsA relationship.

Final can improve the performance of queries as they will not attempt to substitute a final component with its subsets.

Behavior:

if IsA(X, Y) and Final(Y) throw error

EcsOneOf

FLECS_API const ecs_entity_t EcsOneOf

extern

Ensure that a relationship target is a child of the specified entity.

Behavior:

If OneOf(R, O) and R(X, Y), Y must be a child of O
If OneOf(R) and R(X, Y), Y must be a child of R

EcsRelationship

FLECS_API const ecs_entity_t EcsRelationship

extern

Ensure that an entity is always used in a pair as a relationship.

Behavior:

e.add(R) panics
e.add(X, R) panics, unless X has the "Trait" trait

EcsSingleton

FLECS_API const ecs_entity_t EcsSingleton

extern

Mark component as singleton.

Singleton components may only be added to themselves.

EcsSymmetric

FLECS_API const ecs_entity_t EcsSymmetric

extern

Mark relationship as commutative.

Behavior:

if R(X, Y) then R(Y, X)

EcsTarget

FLECS_API const ecs_entity_t EcsTarget

extern

Ensure that an entity is always used in a pair as a target.

Behavior:

e.add(T) panics
e.add(T, X) panics

EcsTrait

FLECS_API const ecs_entity_t EcsTrait

extern

Can be added to components to indicate it is a trait.

Traits are components and/or tags that are added to other components to modify their behavior.