public struct EntityQuery : IDisposable, IEquatable<EntityQuery>

An entity query defines the set of component types that an archetype must contain in order for its chunks and entities to be selected and specifies whether the components accessed through the query are read-only or read-write.

For simple queries, you can create an EntityQuery based on an array of component types. The following example defines a EntityQuery that finds all entities with both Rotation and RotationSpeed components.

The query uses ComponentType.ReadOnly instead of the simpler expression to designate that the system does not write to RotationSpeed. Always specify read-only when possible, since there are fewer constraints on read-only access to data, which can help the Job scheduler execute your Jobs more efficiently.

For more complex queries, you can use an EntityQueryDesc object to create the entity query. A query description provides a flexible query mechanism to specify which archetypes to select based on the following sets of components:

" = All component types in this array must exist in the archetype, and must be enabled on matching entities. " = At least one of the component types in this array must exist in the archetype, and must be enabled on matching entities. " = None of the component types in this array can exist in the archetype, or they must be present and disabled on matching entities. " = All component types in this array must exist in the archetype, and must be disabled on matching entities. " = None of the component types in this array can exist in the archetype " = All of the component types in this array must exist in the archetype, whether or not they are enabled.

For example, the following query includes archetypes containing Rotation and RotationSpeed components, but excludes any archetypes containing a Static component:

Note: Do not include completely optional components in the query description. To handle optional components, use IJobChunk and the ArchetypeChunk.Has() method to determine whether a chunk contains the optional component or not. Since all entities within the same chunk have the same components, you only need to check whether an optional component exists once per chunk -- not once per entity.

Within a system class, use the ComponentSystemBase.GetEntityQuery() function to get a EntityQuery instance.

You can filter entities based on whether they have changed or whether they have a specific value for a shared component. Once you have created an EntityQuery object, you can reset and change the filter settings, but you cannot modify the base query.

Use an EntityQuery for the following purposes:

" To get a native array of the values for a specific IComponentData type for all entities matching the query " To get an native array of the ArchetypeChunk objects matching the query " To schedule an IJobChunk job " To control whether a system updates using [ComponentSystemBase.RequireForUpdate(query)]

SharedComponent

sharedComponent

T

T

SharedComponent

sharedComponent

T