Class ComponentSystemBase
A system provides behavior in an ECS architecture.
Namespace: Unity.Entities
Syntax
public abstract class ComponentSystemBase
Remarks
System implementations should inherit SystemBase, which is a subclass of ComponentSystemBase.
Properties
Enabled
Controls whether this system executes when its OnUpdate function is called.
Declaration
public bool Enabled { get; set; }
Property Value
Type | Description |
---|---|
Boolean | True, if the system is enabled. |
Remarks
The Enabled property is intended for debugging so that you can easily turn on and off systems from the Entity Debugger window. A system with Enabled set to false will not update, even if its ShouldRunSystem() function returns true.
EntityManager
The EntityManager object of the World in which this system exists.
Declaration
public EntityManager EntityManager { get; }
Property Value
Type | Description |
---|---|
EntityManager | The EntityManager for this system. |
EntityQueries
The query objects cached by this system.
Declaration
public EntityQuery[] EntityQueries { get; }
Property Value
Type | Description |
---|---|
EntityQuery[] | A read-only array of the cached EntityQuery objects. |
Remarks
A system caches any queries it implicitly creates through the IJob interfaces or EntityQueryBuilder, that you create explicitly by calling GetEntityQuery(ComponentType[]), or that you add to the system as a required query with RequireForUpdate(EntityQuery). Implicit queries may be created lazily and not exist before a system has run for the first time.
GlobalSystemVersion
The current change version number in this World.
Declaration
public uint GlobalSystemVersion { get; }
Property Value
Type | Description |
---|---|
UInt32 |
Remarks
The system updates the component version numbers inside any ArchetypeChunk instances that this system accesses with write permissions to this value.
LastSystemVersion
The current version of this system.
Declaration
public uint LastSystemVersion { get; }
Property Value
Type | Description |
---|---|
UInt32 | The GlobalSystemVersion the last time this system ran. |
Remarks
LastSystemVersion is updated to match the GlobalSystemVersion whenever a system runs.
When you use
When a system accesses a component and has write permission, it updates the change version of that component type to the current value of LastSystemVersion. The system updates the component type's version whether or not it actually modifies data in any instances of the component type -- this is one reason why you should specify read-only access to components whenever possible.
For efficiency, ECS tracks the change version of component types by chunks, not by individual entities. If a system updates the component of a given type for any entity in a chunk, then ECS assumes that the components of all entities in that chunk could have been changed. Change filtering allows you to save processing time by skipping all entities in an unchanged chunk, but does not support skipping individual entities in a chunk that does contain changes.
Time
The current Time data for this system's world.
Declaration
public TimeData Time { get; }
Property Value
Type | Description |
---|---|
TimeData |
World
The World in which this system exists.
Declaration
public World World { get; }
Property Value
Type | Description |
---|---|
World | The World of this system. |
Methods
GetArchetypeChunkBufferType<T>(Boolean)
Gets the run-time type information required to access an array of buffer components in a chunk.
Declaration
public ArchetypeChunkBufferType<T> GetArchetypeChunkBufferType<T>(bool isReadOnly = false)
where T : struct, IBufferElementData
Parameters
Type | Name | Description |
---|---|---|
Boolean | isReadOnly | Whether the data is only read, not written. Access data as read-only whenever possible. |
Returns
Type | Description |
---|---|
ArchetypeChunkBufferType<T> | An object representing the type information required to safely access buffer components stored in a chunk. |
Type Parameters
Name | Description |
---|---|
T | A struct that implements IBufferElementData. |
Remarks
Pass a GetArchetypeChunkBufferType instance to a job that has access to chunk data, such as an IJobChunk job, to access that type of buffer component inside the job.
GetArchetypeChunkComponentType<T>(Boolean)
Gets the run-time type information required to access an array of component data in a chunk.
Declaration
public ArchetypeChunkComponentType<T> GetArchetypeChunkComponentType<T>(bool isReadOnly = false)
where T : struct, IComponentData
Parameters
Type | Name | Description |
---|---|---|
Boolean | isReadOnly | Whether the component data is only read, not written. Access components as read-only whenever possible. |
Returns
Type | Description |
---|---|
ArchetypeChunkComponentType<T> | An object representing the type information required to safely access component data stored in a chunk. |
Type Parameters
Name | Description |
---|---|
T | A struct that implements IComponentData. |
Remarks
Pass an
GetArchetypeChunkComponentTypeDynamic(ComponentType)
Gets the run-time type information required to access an array of component data in a chunk.
Declaration
public ArchetypeChunkComponentTypeDynamic GetArchetypeChunkComponentTypeDynamic(ComponentType componentType)
Parameters
Type | Name | Description |
---|---|---|
ComponentType | componentType | Type of the component |
Returns
Type | Description |
---|---|
ArchetypeChunkComponentTypeDynamic | An object representing the type information required to safely access component data stored in a chunk. |
Remarks
Pass an ArchetypeChunkComponentTypeDynamic instance to a job that has access to chunk data, such as an IJobChunk job, to access that type of component inside the job.
GetArchetypeChunkEntityType()
Gets the run-time type information required to access the array of Entity objects in a chunk.
Declaration
public ArchetypeChunkEntityType GetArchetypeChunkEntityType()
Returns
Type | Description |
---|---|
ArchetypeChunkEntityType | An object representing the type information required to safely access Entity instances stored in a chunk. |
GetArchetypeChunkSharedComponentType<T>()
Gets the run-time type information required to access a shared component data in a chunk.
Declaration
public ArchetypeChunkSharedComponentType<T> GetArchetypeChunkSharedComponentType<T>()
where T : struct, ISharedComponentData
Returns
Type | Description |
---|---|
ArchetypeChunkSharedComponentType<T> | An object representing the type information required to safely access shared component data stored in a chunk. |
Type Parameters
Name | Description |
---|---|
T | A struct that implements ISharedComponentData. |
GetBufferFromEntity<T>(Boolean)
Gets a BufferFromEntity<T> object that can access a DynamicBuffer<T>.
Declaration
public BufferFromEntity<T> GetBufferFromEntity<T>(bool isReadOnly = false)
where T : struct, IBufferElementData
Parameters
Type | Name | Description |
---|---|---|
Boolean | isReadOnly | Whether the buffer data is only read or is also written. Access data in a read-only fashion whenever possible. |
Returns
Type | Description |
---|---|
BufferFromEntity<T> | An array-like object that provides access to buffers, indexed by Entity. |
Type Parameters
Name | Description |
---|---|
T | The type of IBufferElementData stored in the buffer. |
Remarks
Assign the returned object to a field of your Job struct so that you can access the contents of the buffer in a Job.
See Also
GetComponentDataFromEntity<T>(Boolean)
Gets an dictionary-like container containing all components of type T, keyed by Entity.
Declaration
public ComponentDataFromEntity<T> GetComponentDataFromEntity<T>(bool isReadOnly = false)
where T : struct, IComponentData
Parameters
Type | Name | Description |
---|---|---|
Boolean | isReadOnly | Whether the data is only read, not written. Access data as read-only whenever possible. |
Returns
Type | Description |
---|---|
ComponentDataFromEntity<T> | All component data of type T. |
Type Parameters
Name | Description |
---|---|
T | A struct that implements IComponentData. |
GetEntityQuery(NativeArray<ComponentType>)
Gets the cached query for the specified component types, if one exists; otherwise, creates a new query instance and caches it.
Declaration
protected EntityQuery GetEntityQuery(NativeArray<ComponentType> componentTypes)
Parameters
Type | Name | Description |
---|---|---|
NativeArray<ComponentType> | componentTypes | An array of component types. |
Returns
Type | Description |
---|---|
EntityQuery | The new or cached query. |
GetEntityQuery(ComponentType[])
Gets the cached query for the specified component types, if one exists; otherwise, creates a new query instance and caches it.
Declaration
protected EntityQuery GetEntityQuery(params ComponentType[] componentTypes)
Parameters
Type | Name | Description |
---|---|---|
ComponentType[] | componentTypes | An array or comma-separated list of component types. |
Returns
Type | Description |
---|---|
EntityQuery | The new or cached query. |
GetEntityQuery(EntityQueryDesc[])
Combines an array of query description objects into a single query.
Declaration
protected EntityQuery GetEntityQuery(params EntityQueryDesc[] queryDesc)
Parameters
Type | Name | Description |
---|---|---|
EntityQueryDesc[] | queryDesc | An array of query description objects to be combined to define the query. |
Returns
Type | Description |
---|---|
EntityQuery | The new or cached query. |
Remarks
This function looks for a cached query matching the combined query descriptions, and returns it if one exists; otherwise, the function creates a new query instance and caches it.
GetSingleton<T>()
Gets the value of a singleton component.
Declaration
public T GetSingleton<T>()
where T : struct, IComponentData
Returns
Type | Description |
---|---|
T | The component. |
Type Parameters
Name | Description |
---|---|
T | The IComponentData subtype of the singleton component. |
See Also
GetSingletonEntity<T>()
Gets the Entity instance for a singleton.
Declaration
public Entity GetSingletonEntity<T>()
Returns
Type | Description |
---|---|
Entity | The entity associated with the specified singleton component. |
Type Parameters
Name | Description |
---|---|
T | The Type of the singleton component. |
See Also
HasSingleton<T>()
Checks whether a singelton component of the specified type exists.
Declaration
public bool HasSingleton<T>()
where T : struct, IComponentData
Returns
Type | Description |
---|---|
Boolean | True, if a singleton of the specified type exists in the current World. |
Type Parameters
Name | Description |
---|---|
T | The IComponentData subtype of the singleton component. |
OnCreate()
Called when this system is created.
Declaration
protected virtual void OnCreate()
Remarks
Implement an OnCreate() function to set up system resources when it is created.
OnCreate is invoked before the the first time OnStartRunning() and OnUpdate are invoked.
OnCreateForCompiler()
Declaration
protected virtual void OnCreateForCompiler()
OnDestroy()
Called when this system is destroyed.
Declaration
protected virtual void OnDestroy()
Remarks
Systems are destroyed when the application shuts down, the World is destroyed, or you call DestroySystem(ComponentSystemBase). In the Unity Editor, system destruction occurs when you exit Play Mode and when scripts are reloaded.
OnStartRunning()
Called before the first call to OnUpdate and when a system resumes updating after being stopped or disabled.
Declaration
protected virtual void OnStartRunning()
Remarks
If the EntityQuery objects defined for a system do not match any existing entities then the system skips updates until a successful match is found. Likewise, if you set Enabled to false, then the system stops running. In both cases, OnStopRunning() is called when a running system stops updating; OnStartRunning is called when it starts updating again.
OnStopRunning()
Called when this system stops running because no entities match the system's EntityQuery objects or because you change the system Enabled property to false.
Declaration
protected virtual void OnStopRunning()
Remarks
If the EntityQuery objects defined for a system do not match any existing entities then the system skips updating until a successful match is found. Likewise, if you set Enabled to false, then the system stops running. In both cases, OnStopRunning() is called when a running system stops updating; OnStartRunning is called when it starts updating again.
RequireForUpdate(EntityQuery)
Adds a query that must return entities for the system to run. You can add multiple required queries to a system; all of them must match at least one entity for the system to run.
Declaration
public void RequireForUpdate(EntityQuery query)
Parameters
Type | Name | Description |
---|---|---|
EntityQuery | query | A query that must match entities this frame in order for this system to run. |
Remarks
Any queries added through RequireforUpdate override all other queries cached by this system. In other words, if any required query does not find matching entities, the update is skipped even if another query created for the system (either explicitly or implicitly) does match entities and vice versa.
RequireSingletonForUpdate<T>()
Require that a specific singleton component exist for this system to run.
Declaration
public void RequireSingletonForUpdate<T>()
Type Parameters
Name | Description |
---|---|
T | The IComponentData subtype of the singleton component. |
SetSingleton<T>(T)
Sets the value of a singleton component.
Declaration
public void SetSingleton<T>(T value)
where T : struct, IComponentData
Parameters
Type | Name | Description |
---|---|---|
T | value | A component containing the value to assign to the singleton. |
Type Parameters
Name | Description |
---|---|
T | The IComponentData subtype of the singleton component. |
See Also
ShouldRunSystem()
Reports whether any of this system's entity queries currently match any chunks. This function is used internally to determine whether the system's OnUpdate function can be skipped.
Declaration
public bool ShouldRunSystem()
Returns
Type | Description |
---|---|
Boolean | True, if the queries in this system match existing entities or the system has the AlwaysUpdateSystemAttribute. |
Remarks
A system without any queries also returns true. Note that even if this function returns true, other factors may prevent a system from updating. For example, a system will not be updated if its Enabled property is false.
Update()
Executes the system immediately.
Declaration
public abstract void Update()
Remarks
The exact behavior is determined by this system's specific subclass.