Method GetChangeVersion

GetChangeVersion<T>(ComponentTypeHandle<T>)

Gets the change version number assigned to the specified type of component in this chunk.

Declaration

public uint GetChangeVersion<T>(ComponentTypeHandle<T> chunkComponentTypeHandle)
    where T : IComponentData

Parameters

Type	Name	Description
ComponentTypeHandle<T>	chunkComponentTypeHandle	An object containing type and job safety information. Create this object by calling GetComponentTypeHandle<T>(Boolean) immediately before scheduling a job. Pass the object to a job using a public field you define as part of the job struct.

Returns

Type	Description
UInt32	The current version number of the specified component, which is the version set the last time a system accessed a component of that type in this chunk with write privileges. Returns 0 if the chunk does not contain a component of the specified type.

Type Parameters

Name	Description
T	The data type of component T.

Remarks

Every time a system accesses components in a chunk, the system updates the change version of any component types to which it has write access with the current GlobalSystemVersion. (A system updates the version whether or not you actually write any component data -- always specify read-only access when possible.)

You can use the change version to filter out entities that have not changed since the last time a system ran. Implement change filtering using one of the following:

• Entities.ForEach.WithChangeFilter(ComponentType)
• AddChangedVersionFilter(ComponentType)
• DidChange<T>(ComponentTypeHandle<T>, UInt32) in an IJobChunk job.

Note that change versions are stored at the chunk level. Thus when you use change filtering, the query system excludes or includes whole chunks not individual entities.

GetChangeVersion(DynamicComponentTypeHandle)

Gets the change version number assigned to the specified type of component in this chunk.

Declaration

public uint GetChangeVersion(DynamicComponentTypeHandle chunkComponentType)

Parameters

Type	Name	Description
DynamicComponentTypeHandle	chunkComponentType	An object containing type and job safety information. Create this object by calling GetDynamicComponentTypeHandle(ComponentType) immediately before scheduling a job. Pass the object to a job using a public field you define as part of the job struct.

Returns

Type	Description
UInt32	The current version number of the specified component, which is the version set the last time a system accessed a component of that type in this chunk with write privileges. Returns 0 if the chunk does not contain a component of the specified type.

Remarks

Every time a system accesses components in a chunk, the system updates the change version of any component types to which it has write access with the current GlobalSystemVersion. (A system updates the version whether or not you actually write any component data -- always specify read-only access when possible.)

You can use the change version to filter out entities that have not changed since the last time a system ran. Implement change filtering using one of the following:

• Entities.ForEach.WithChangeFilter(ComponentType)
• AddChangedVersionFilter(ComponentType)
• DidChange<T>(ComponentTypeHandle<T>, UInt32) in an IJobChunk job.

Note that change versions are stored at the chunk level. Thus when you use change filtering, the query system excludes or includes whole chunks not individual entities.

GetChangeVersion<T>(BufferTypeHandle<T>)

Gets the change version number assigned to the specified type of dynamic buffer component in this chunk.

Declaration

public uint GetChangeVersion<T>(BufferTypeHandle<T> chunkBufferTypeHandle)
    where T : struct, IBufferElementData

Parameters

Type	Name	Description
BufferTypeHandle<T>	chunkBufferTypeHandle	An object containing type and job safety information. Create this object by calling GetBufferTypeHandle<T>(Boolean) immediately before scheduling a job. Pass the object to a job using a public field you define as part of the job struct.

Returns

Type	Description
UInt32	The current version number of the specified dynamic buffer type, which is the version set the last time a system accessed a buffer component of that type in this chunk with write privileges. Returns 0 if the chunk does not contain a buffer component of the specified type.

Type Parameters

Name	Description
T	The data type of component T.

Remarks

Every time a system accesses components in a chunk, the system updates the change version of any component types to which it has write access with the current GlobalSystemVersion. (A system updates the version whether or not you actually write any component data -- always specify read-only access when possible.)

You can use the change version to filter out entities that have not changed since the last time a system ran. Implement change filtering using one of the following:

• Entities.ForEach.WithChangeFilter(ComponentType)
• AddChangedVersionFilter(ComponentType)
• DidChange<T>(ComponentTypeHandle<T>, UInt32) in an IJobChunk job.

Note that change versions are stored at the chunk level. Thus if you use change filtering, the query system excludes or includes whole chunks not individual entities.

GetChangeVersion<T>(SharedComponentTypeHandle<T>)

Gets the change version number assigned to the specified type of shared component in this chunk.

Declaration

public uint GetChangeVersion<T>(SharedComponentTypeHandle<T> chunkSharedComponentData)
    where T : struct, ISharedComponentData

Parameters

Type	Name	Description
SharedComponentTypeHandle<T>	chunkSharedComponentData	An object containing type and job safety information. Create this object by calling GetSharedComponentTypeHandle<T>() immediately before scheduling a job. Pass the object to a job using a public field you define as part of the job struct.

Returns

Type	Description
UInt32	The current version number of the specified shared component, which is the version set the last time a system accessed a component of that type in this chunk with write privileges. Returns 0 if the chunk does not contain a shared component of the specified type.

Type Parameters

Name	Description
T	The data type of shared component T.

Remarks

Shared components behave differently than other types of components in terms of change versioning because changing the value of a shared component can move an entity to a different chunk. If the change results in an entity moving to a different chunk, then only the order version is updated (for both the original and the receiving chunk). If you change the shared component value for all entities in a chunk at once, the entities remain in their current chunk. The change version for that chunk is updated and the order version is unaffected.

GetChangeVersion(DynamicSharedComponentTypeHandle)

Gets the change version number assigned to the specified type of shared component in this chunk.

Declaration

public uint GetChangeVersion(DynamicSharedComponentTypeHandle chunkSharedComponentData)

Parameters

Type	Name	Description
DynamicSharedComponentTypeHandle	chunkSharedComponentData	An object containing type and job safety information. Create this object by calling GetDynamicSharedComponentTypeHandle(ComponentType).

Returns

Type	Description
UInt32	The current version number of the specified shared component, which is the version set the last time a system accessed a component of that type in this chunk with write privileges. Returns 0 if the chunk does not contain a shared component of the specified type.

Remarks

Shared components behave differently than other types of components in terms of change versioning because changing the value of a shared component can move an entity to a different chunk. If the change results in an entity moving to a different chunk, then only the order version is updated (for both the original and the receiving chunk). If you change the shared component value for all entities in a chunk at once, the entities remain in their current chunk. The change version for that chunk is updated and the order version is unaffected.