Unity Entities

https://docs.unity3d.com/Packages/com.unity.entities@1.4/
Admin
The Unity Entities package is part of Unity's Data-Oriented Technology Stack (DOTS), providing a...
Tokens:1,222,169
Snippets:11,708
Trust Score:10
Update:1 week ago
Show doc for...
Tokens:
Raw
### Start(ref DownloadStatus)

Source: https://docs.unity3d.com/Packages/com.unity.entities%401.4/api/Unity.Entities.Content.ContentDownloadService.DownloadOperation.Start.html

Starts the download operation and updates the provided status.

```APIDOC
## Start(ref DownloadStatus)

### Description
Starts the download operation.

### Method
Start

### Signature
public void Start(ref ContentDownloadService.DownloadStatus status)

### Parameters
- **status** (ContentDownloadService.DownloadStatus) - The status will be updated when Start is called.

```

--------------------------------

### Custom ICustomBootstrap implementation

Source: https://docs.unity3d.com/Packages/com.unity.entities%401.4/changelog/CHANGELOG.html

Example of implementing ICustomBootstrap to replace default world initialization. It creates a custom world, gets all systems, adds them to root level system groups, and updates the player loop.

```csharp
class MyCustomBootStrap : ICustomBootstrap
{
    public bool Initialize(string defaultWorldName)
    {
        Debug.Log("Executing bootstrap");
        var world = new World("Custom world");
        World.DefaultGameObjectInjectionWorld = world;
        var systems = DefaultWorldInitialization.GetAllSystems(WorldSystemFilterFlags.Default);

        DefaultWorldInitialization.AddSystemsToRootLevelSystemGroups(world, systems);
        ScriptBehaviourUpdateOrder.UpdatePlayerLoop(world);
        return true;
    }
}
```

--------------------------------

### Example: Building a query with WithAny

Source: https://docs.unity3d.com/Packages/com.unity.entities%401.4/api/Unity.Entities.EntityQueryBuilder.WithAny.html

Example showing how to use WithAny to require an entity to have at least one of the specified optional components.

```csharp
var query = new EntityQueryBuilder(Allocator.Temp)
    .WithAll<ObjectPosition>()
    .WithAny<ObjectUniformScale, ObjectNonUniformScale>()
    .WithAny<ObjectCompositeScale>()
    .Build(this);
```

--------------------------------

### GetServerGUID()

Source: https://docs.unity3d.com/Packages/com.unity.entities%401.4/api/Unity.Entities.Build.DotsGlobalSettings.GetServerGUID.html

Gets the GUID of the Server asset. Returns the GUID as a Hash128 value.

```APIDOC
## GetServerGUID()

### Description
Gets the GUID of the Server asset.

### Method
GetServerGUID

### Declaration
```csharp
public Hash128 GetServerGUID()
```

### Returns
| Type | Description |
|------|-------------|
| Hash128 | Returns the GUID of the Server asset. |
```

--------------------------------

### OnCreate()

Source: https://docs.unity3d.com/Packages/com.unity.entities%401.4/api/Unity.Entities.ComponentSystemBase.OnCreate.html

Called when this system is created. Implement this method to set up system resources. It is invoked before the first time OnStartRunning() and OnUpdate are invoked.

```APIDOC
## OnCreate()

### Description
Called when this system is created. Implement an OnCreate() function to set up system resources when it is created. OnCreate is invoked before the first time OnStartRunning() and OnUpdate are invoked.

### Method
OnCreate

### Declaration
```csharp
[RequiredMember]
protected virtual void OnCreate()
```

### Remarks
Implement an OnCreate() function to set up system resources when it is created. OnCreate is invoked before the first time OnStartRunning() and OnUpdate are invoked.
```

--------------------------------

### ComponentSystemBase()

Source: https://docs.unity3d.com/Packages/com.unity.entities%401.4/api/Unity.Entities.ComponentSystemBase.-ctor.html

Initializes and returns an instance of a system.

```APIDOC
## ComponentSystemBase()

### Description
Initializes and returns an instance of a system.

### Declaration
```csharp
[RequiredMember]
public ComponentSystemBase()
```

```

--------------------------------

### public Hash128 SceneGUID { get; }

Source: https://docs.unity3d.com/Packages/com.unity.entities%401.4/api/Unity.Scenes.SubScene.SceneGUID.html

Gets the GUID of the SceneAsset as a Hash128 value.

```APIDOC
## Property SceneGUID

### Description
Represents the GUID of the SceneAsset.

### Declaration
```csharp
public Hash128 SceneGUID { get; }
```

### Property Value
| Type | Description |
|------|-------------|
| Hash128 | The GUID of the SceneAsset. |
```

--------------------------------

### GetSceneGUID()

Source: https://docs.unity3d.com/Packages/com.unity.entities%401.4/api/Unity.Entities.IBaker.GetSceneGUID.html

Gets the GUID of the current scene. Returns a Hash128 representing the scene GUID.

```APIDOC
## GetSceneGUID()

### Description
Gets the GUID of the current scene.

### Declaration
```csharp
public Hash128 GetSceneGUID()
```

### Returns
| Type | Description |
|------|-------------|
| Hash128 | The scene GUID |
```

--------------------------------

### Initialize(string, bool)

Source: https://docs.unity3d.com/Packages/com.unity.entities%401.4/api/Unity.Entities.DefaultWorldInitialization.html

Initializes the default world or runs ICustomBootstrap if one is available.

```APIDOC
## Initialize(string, bool)

### Description
Initializes the default world or runs ICustomBootstrap if one is available.

### Method
Initialize

### Parameters
- **worldName** (string) - The name of the default world.
- **editorWorld** (bool) - Whether this is an editor world.

### Return Value
void
```

--------------------------------

### Using WithAllChunkComponent to Query Chunk Components

Source: https://docs.unity3d.com/Packages/com.unity.entities%401.4/api/Unity.Entities.EntityQueryBuilder.WithAllChunkComponent.html

Example showing how to create entities with a standard component and a chunk component, and how to build queries using WithAll<Player> and WithAllChunkComponent<Player> to match each entity type respectively.

```csharp
var entityWithPlayerComponent = EntityManager.CreateEntity();
EntityManager.AddComponent<Player>(entityWithPlayerComponent);
var entityWithPlayerChunkComponent = EntityManager.CreateEntity();
EntityManager.AddComponent(entityWithPlayerChunkComponent, ComponentType.ChunkComponent<Player>());
// This query will only match entityWithPlayerComponent
var playerQuery = new EntityQueryBuilder(Allocator.Temp)
.WithAll<Player>()
.Build(this);
// This query will only match entityWithPlayerChunkComponent
var chunkPlayerQuery = new EntityQueryBuilder(Allocator.Temp)
.WithAllChunkComponent<Player>()
.Build(this);
```

--------------------------------

### EntityIndexInQuery Example

Source: https://docs.unity3d.com/Packages/com.unity.entities%401.4/manual/iterating-data-ijobentity.html

Example of using the EntityIndexInQuery attribute in an IJobEntity to get the current index in query for array access.

```APIDOC
## IJobEntity EntityIndexInQuery Example

### Description
Demonstrates how to use the `[EntityIndexInQuery]` attribute on an `int` parameter in `Execute` to get the current index in query for the current entity iteration.

### Code
```csharp
[BurstCompile]
partial struct CopyPositionsJob : IJobEntity
{
    public NativeArray<float3> copyPositions;

    // Iterates over all `LocalToWorld` and stores their position inside `copyPositions`.
    // The [EntityIndexInQuery] attribute provides the index of the current entity within the query results.
    public void Execute([EntityIndexInQuery] int entityIndexInQuery, in LocalToWorld localToWorld)
    {
        copyPositions[entityIndexInQuery] = localToWorld.Position;
    }
}

[RequireMatchingQueriesForUpdate]
public partial struct EntityInQuerySystem : ISystem
{
    // This query should match `CopyPositionsJob` parameters
    EntityQuery query;

    public void OnCreate(ref SystemState state)
    {
        // Get query that matches `CopyPositionsJob` parameters
        query = state.GetEntityQuery(ComponentType.ReadOnly<LocalToWorld>());
    }

    public void OnUpdate(ref SystemState state)
    {
        // Get a native array equal to the size of the amount of entities found by the query.
        var positions = new NativeArray<float3>(query.CalculateEntityCount(), state.WorldUnmanaged.UpdateAllocator.ToAllocator);

        // Schedule job on parallel threads for this array.
        // The EntityIndexInQuery parameter ensures each entity gets a unique index for array access.
        new CopyPositionsJob{copyPositions = positions}.ScheduleParallel();

        // Dispose the array of positions found by the job.
        positions.Dispose(state.Dependency);
    }
}
```
```

--------------------------------

### Initialize(string, bool)

Source: https://docs.unity3d.com/Packages/com.unity.entities%401.4/api/Unity.Entities.DefaultWorldInitialization.Initialize.html

Documentation for the static method Initialize(string, bool) that initializes the default world or runs ICustomBootstrap if available.

```APIDOC
## Initialize(string, bool)

### Description
Initializes the default world or runs ICustomBootstrap if one is available.

### Method
Initialize

### Signature
public static World Initialize(string defaultWorldName, bool editorWorld = false)

### Parameters
- **defaultWorldName** (string) - Required - The name of the world that will be created. Unless there is a custom bootstrap.
- **editorWorld** (bool) - Optional - Editor worlds by default only include systems with [WorldSystemFilter(WorldSystemFilterFlags.Editor)]. If editorWorld is true, ICustomBootstrap will not be used.

### Returns
- **World** - The initialized World object.
```

--------------------------------

### GetPathFromGUID(Hash128)

Source: https://docs.unity3d.com/Packages/com.unity.entities%401.4/api/Unity.Scenes.ResourceCatalogData.html

Gets the path of a resource from a GUID.

```APIDOC
## GetPathFromGUID(Hash128)

### Description
Gets the path of a resource from a GUID.

### Method
GetPathFromGUID

### Parameters
#### Parameters
- **guid** (Hash128) - The GUID of the resource.

### Returns
- **string** - The path of the resource.

```

--------------------------------

### GetPathFromGUID(Hash128)

Source: https://docs.unity3d.com/Packages/com.unity.entities%401.4/api/Unity.Scenes.ResourceCatalogData.GetPathFromGUID.html

Gets the path of a resource from a GUID.

```APIDOC
## GetPathFromGUID(Hash128)

### Description
Gets the path of a resource from a GUID.

### Method
GetPathFromGUID

### Signature
public string GetPathFromGUID(Hash128 guid)

### Parameters
- **guid** (Hash128) - The GUID of the resource.

### Returns
- **string** - Returns the path of the resource.

```

--------------------------------

### OnCreate(ref SystemState)

Source: https://docs.unity3d.com/Packages/com.unity.entities%401.4/api/Unity.Entities.ISystem.OnCreate.html

Called when this system is created. Implement this method to set up system resources. It is invoked before OnStartRunning and OnUpdate.

```APIDOC
## OnCreate(ref SystemState)

### Description
Called when this system is created. Implement an `OnCreate` function to set up system resources when it is created. `OnCreate` is invoked before the first time `OnStartRunning(ref SystemState)` and `OnUpdate(ref SystemState)` are invoked.

### Method
OnCreate

### Signature
```csharp
[RequiredMember]
void OnCreate(ref SystemState state)
```

### Parameters
- **state** (SystemState) - Required - The SystemState backing this system instance.

### Remarks
Implement an `OnCreate` function to set up system resources when it is created. `OnCreate` is invoked before the first time `OnStartRunning(ref SystemState)` and `OnUpdate(ref SystemState)` are invoked.
```

--------------------------------

### BeginSimulationEntityCommandBufferSystem.OnCreate()

Source: https://docs.unity3d.com/Packages/com.unity.entities%401.4/api/Unity.Entities.BeginSimulationEntityCommandBufferSystem.html

Initializes this command buffer system. This method is called when the system is created and sets up the command buffer system.

```APIDOC
## OnCreate()

### Description
Initializes this command buffer system.

### Method
OnCreate()

### Syntax
```csharp
protected override void OnCreate()
```

### Parameters
None.

### Returns
void

### Remarks
This method is called when the system is created and performs initialization for the command buffer system.
```

--------------------------------

### EntityPrefabReference.AssetGUID

Source: https://docs.unity3d.com/Packages/com.unity.entities%401.4/api/Unity.Entities.Serialization.EntityPrefabReference.AssetGUID.html

Gets the prefab GUID associated with the EntityPrefabReference.

```APIDOC
## Property AssetGUID

### Description
Returns the prefab GUID.

### Declaration
```csharp
public Hash128 AssetGUID { get; }
```

### Property Value
| Type | Description |
|------|-------------|
| Hash128 | The prefab GUID. |

```

--------------------------------

### Init(RemoteContentLocation, string, string)

Source: https://docs.unity3d.com/Packages/com.unity.entities%401.4/api/Unity.Entities.Content.ContentDownloadService.DownloadOperation.Init.html

Initializes the download operation with the information needed to start.

```APIDOC
## Init(RemoteContentLocation, string, string)

### Description
Initializes the download operation with the information needed to start.

### Declaration
```csharp
public void Init(RemoteContentLocation loc, string tmpPath, string finalPath)
```

### Parameters
- **loc** (RemoteContentLocation) - The content location.
- **tmpPath** (string) - The temporary path to download to.
- **finalPath** (string) - The final path to copy to once the download completes.

```

--------------------------------

### GUID

Source: https://docs.unity3d.com/Packages/com.unity.entities%401.4/api/Unity.Entities.Build.IEntitiesPlayerSettings.GUID.html

Gets the unique ID of the settings asset.

```APIDOC
## GUID

### Description
Gets the unique ID of the settings asset.

### Declaration
```
Hash128 GUID { get; }
```

### Property Value
- **Hash128** - The unique ID of the settings asset.
```

--------------------------------

### GetSubScenes(GUID)

Source: https://docs.unity3d.com/Packages/com.unity.entities%401.4/api/Unity.Scenes.Editor.EditorEntityScenes.html

Gets all the sub scenes embedded in a scene.

```APIDOC
## GetSubScenes(GUID)

### Description
Gets all the sub scenes embedded in a scene.

### Method
GetSubScenes

### Parameters
- **GUID** (GUID) - The GUID of the scene to get sub scenes from.

### Returns
- The sub scenes embedded in the scene.
```

--------------------------------

### BeginFixedStepSimulationEntityCommandBufferSystem.OnCreate()

Source: https://docs.unity3d.com/Packages/com.unity.entities%401.4/api/Unity.Entities.BeginFixedStepSimulationEntityCommandBufferSystem.html

Initializes the command buffer system. This method is called when the system is created and sets up any necessary resources.

```APIDOC
## BeginFixedStepSimulationEntityCommandBufferSystem.OnCreate()

### Description
Initializes this command buffer system. This method is called when the system is created and sets up any necessary resources.

### Method
OnCreate()

### Parameters
None

### Return Value
void

### Remarks
This method is part of the system lifecycle and is called automatically by the Unity ECS framework.
```

--------------------------------

### GetSceneGUID

Source: https://docs.unity3d.com/Packages/com.unity.entities%401.4/api/Unity.Scenes.SceneSystem.html

Method to get the asset GUID for a scene path or name.

```APIDOC
## GetSceneGUID

### Description
Get the guid for a scene path or name. This is a slow method - it is best to use the guid directly.

### Signature
```csharp
public static Hash128 GetSceneGUID(ref SystemState state, string scenePathOrName)
```

### Parameters
- **state** (SystemState) - Reference to the system state.
- **scenePathOrName** (string) - The path or name of the scene.

### Returns
- **Hash128** - The asset GUID of the scene.
```

--------------------------------

### GetSubScenes(GUID)

Source: https://docs.unity3d.com/Packages/com.unity.entities%401.4/api/Unity.Scenes.Editor.EditorEntityScenes.GetSubScenes.html

Gets all the sub scenes embedded in a scene. This method takes a scene GUID and returns an array of Hash128 values representing the sub scenes.

```APIDOC
## GetSubScenes(GUID)

### Description
Gets all the sub scenes embedded in a scene.

### Method
GetSubScenes

### Signature
public static Hash128[] GetSubScenes(GUID guid)

### Parameters
- **guid** (GUID) - The GUID of the scene

### Returns
- **Hash128[]** - A list of all sub scenes embedded in the given scene
```

--------------------------------

### BeginPresentationEntityCommandBufferSystem.OnCreate()

Source: https://docs.unity3d.com/Packages/com.unity.entities%401.4/api/Unity.Entities.BeginPresentationEntityCommandBufferSystem.html

Initializes this command buffer system. This method is called when the system is created and sets up the command buffer system.

```APIDOC
## BeginPresentationEntityCommandBufferSystem.OnCreate()

### Description
Initializes this command buffer system. This method is called when the system is created and sets up the command buffer system.

### Method
OnCreate()

### Parameters
None

### Returns
void

### Remarks
This method is part of the EntityCommandBufferSystem lifecycle and is called automatically by the ECS framework.
```

--------------------------------

### BuildConfigurationGUID

Source: https://docs.unity3d.com/Packages/com.unity.entities%401.4/api/Unity.Scenes.SceneSystemData.BuildConfigurationGUID.html

Gets the GUID of the Unity.Build.BuildConfiguration applied on the World. This field is of type Hash128.

```APIDOC
## BuildConfigurationGUID

### Description
Gets the GUID of the Unity.Build.BuildConfiguration applied on the World.

### Syntax
```csharp
public Hash128 BuildConfigurationGUID
```

### Returns
| Type | Description |
|------|-------------|
| Hash128 | The GUID of the build configuration. |

```

--------------------------------

### StartDownload(string, string)

Source: https://docs.unity3d.com/Packages/com.unity.entities%401.4/api/Unity.Entities.Content.ContentDownloadService.DownloadOperation.StartDownload.html

Called when the operation can begin downloading its data. This method is protected and abstract, intended to be overridden by derived classes.

```APIDOC
## StartDownload(string remotePath, string localTmpPath)

### Description
Called when the operation can begin downloading its data.

### Declaration
```csharp
protected abstract void StartDownload(string remotePath, string localTmpPath)
```

### Parameters
- **remotePath** (string) - The remote path of the data. This is typically a url.
- **localTmpPath** (string) - The local path to download the data to. This file will be moved to the final path once completed.

```

--------------------------------

### GetSettingsAsset(Hash128)

Source: https://docs.unity3d.com/Packages/com.unity.entities%401.4/api/Unity.Entities.Build.DotsGlobalSettings.GetSettingsAsset.html

Gets the IEntitiesPlayerSettings settings asset corresponding to the given guid.

```APIDOC
## GetSettingsAsset(Hash128)

### Description
Gets the IEntitiesPlayerSettings settings asset corresponding to the guid.

### Declaration
```csharp
public IEntitiesPlayerSettings GetSettingsAsset(Hash128 guid)
```

### Parameters
- **guid** (Hash128) - The unique ID of the build settings asset.

### Returns
- **IEntitiesPlayerSettings** - Returns the settings asset corresponding to the guid, or null if not found.
```

--------------------------------

### BeginInitializationEntityCommandBufferSystem.OnCreate()

Source: https://docs.unity3d.com/Packages/com.unity.entities%401.4/api/Unity.Entities.BeginInitializationEntityCommandBufferSystem.html

Initializes this command buffer system. This method is called when the system is created and sets up the command buffer system.

```APIDOC
## OnCreate()

### Description
Initializes this command buffer system. This method is called when the system is created and sets up the command buffer system.

### Method
OnCreate

### Syntax
csharp
protected override void OnCreate()


### Parameters
None

### Returns
void

### Remarks
This method is part of the SystemBase lifecycle and is called once when the system is created. It is used to initialize the command buffer system.
```

--------------------------------

### Complete HelloWorld.cs script

Source: https://docs.unity3d.com/Packages/com.unity.entities%401.4/manual/ecs-workflow-example-starter.html

Defines an unmanaged ECS component HelloComponent with a FixedString32Bytes message and an ExampleSystem that creates an entity, adds the component, sets its name, and logs the message in OnUpdate. The entity name is only available in the Editor.

```C#
using Unity.Entities;
using Unity.Collections;
using UnityEngine;

// This is an example of an unmanaged ECS component.
public struct HelloComponent : IComponentData
{
    // FixedString32Bytes is used instead of string, because
    // struct IComponentData can only contain unmanaged types.
    public FixedString32Bytes Message;
}

public partial struct ExampleSystem : ISystem
{
    public void OnCreate(ref SystemState state)
    {
        var entity = state.EntityManager.CreateEntity();
        // Initialize and add a HelloComponent component to the entity.
        state.EntityManager.AddComponentData(entity, new HelloComponent 
            { Message = "Hello ECS World" });
        // Set the name of the entity to make it easier to identify it.
        // Note: the entity Name property only exists in the Editor.
        state.EntityManager.SetName(entity, "Hello World Entity");
    }

    public void OnUpdate(ref SystemState state)
    {
        // The query retrieves all entities with a HelloComponent component.
        foreach (var message in
                    SystemAPI.Query<RefRO<HelloComponent>>())
        {
            Debug.Log(message.ValueRO.Message);
        }
    }
}
```

--------------------------------

### EntitiesJournaling.Records.Range(int, int)

Source: https://docs.unity3d.com/Packages/com.unity.entities%401.4/api/Unity.Entities.EntitiesJournaling.Records.html

Gets a number of records starting from a specified index.

```APIDOC
## Method: Range(int, int)

### Description
Gets a number of records starting from the specified index.

### Syntax
```csharp
public static IEnumerable<Record> Range(int index, int count)
```

### Parameters
- **index** (int) - The starting index.
- **count** (int) - The number of records to retrieve.

### Returns
- **IEnumerable<Record>** - The requested records.
```

--------------------------------

### RemoveRange (int index, int count) method declaration and usage

Source: https://docs.unity3d.com/Packages/com.unity.entities%401.4/api/Unity.Entities.DynamicBuffer-1.RemoveRange.html

The declaration of the RemoveRange method, which removes the specified number of elements starting at the given index. The example call removes five elements starting from the 'start' index.

```csharp
public void RemoveRange(int index, int count)

```

```csharp
buffer.RemoveRange(start, 5);

```

--------------------------------

### Chaining WithAllRW calls (compact formatting)

Source: https://docs.unity3d.com/Packages/com.unity.entities%401.4/api/Unity.Entities.EntityQueryBuilder.WithAllRW.html

A second rendering of the same chaining example with reduced indentation. It shows the same sequence of WithAll and WithAllRW calls and the Build call.

```csharp
var query = new EntityQueryBuilder(Allocator.Temp)
.WithAll<Friction>()
.WithAllRW<ObjectPosition, ObjectVelocity>()
.WithAllRW<ObjectRotation, ObjectRotationSpeed>()
.Build(this);
```

--------------------------------

### GetClientGUID()

Source: https://docs.unity3d.com/Packages/com.unity.entities%401.4/api/Unity.Entities.Build.DotsGlobalSettings.GetClientGUID.html

Gets the GUID of the Client asset. Returns an invalid Hash128 if there is no provider for the client target.

```APIDOC
## GetClientGUID()

### Description
Gets the GUID of the Client asset.

### Declaration
```csharp
public Hash128 GetClientGUID()
```

### Returns
| Type | Description |
|------|-------------|
| Hash128 | Returns the GUID of the Client asset. |

### Remarks
If there is no provider for the client target, returns an invalid Hash128 value.
```

--------------------------------

### IsStarted Property

Source: https://docs.unity3d.com/Packages/com.unity.entities%401.4/api/Unity.Entities.Content.ContentDownloadService.DownloadOperation.IsStarted.html

Gets a value indicating whether the download operation has been started. Returns false if the operation is queued.

```APIDOC
## IsStarted Property

### Description
Gets a value indicating whether the download operation has been started. This will be false if the operation is queued.

### Declaration
```csharp
public bool IsStarted { get; }
```

### Property Value
| Type | Description |
|------|-------------|
| bool | True if the operation has been started; otherwise, false. |

```

--------------------------------

### Initialize(int, int, bool, int)

Source: https://docs.unity3d.com/Packages/com.unity.entities%401.4/api/Unity.Entities.Scratchpad.Initialize.html

Initializes a Scratchpad with the specified number of allocators, initial size, global flag, and global index.

```APIDOC
## Initialize(int numScratchpadAllocators, int initialSizeInBytes = 32768, bool isGlobal = false, int globalIndex = 0)

### Description
Initializes a Scratchpad with the specified number of allocators, initial size, global flag, and global index.

### Declaration
```
[ExcludeFromBurstCompatTesting("Accesses managed delegate")]
public void Initialize(int numScratchpadAllocators, int initialSizeInBytes = 32768, bool isGlobal = false, int globalIndex = 0)
```

### Parameters
- **numScratchpadAllocators** (int) - Required - The number of ScratchpadAllocators the created Scratchpad should contain.
- **initialSizeInBytes** (int) - Optional - The initial size of the Scratchpad in bytes. Set to 32,768 by default.
- **isGlobal** (bool) - Optional - Flag indicating if the allocator is a global allocator.
- **globalIndex** (int) - Optional - Base index into the global function table of the allocator to be created.

```

--------------------------------

### Get a single component with EntityManager.GetComponentData

Source: https://docs.unity3d.com/Packages/com.unity.entities%401.4/manual/components-read-and-write.html

Use EntityManager.GetComponentData<T> to read a component value of a single entity on the main thread. The example creates an entity, adds a Rotation component, then retrieves it.

```csharp
 public partial struct GetComponentOnSingleEntitySystemExample : ISystem
{
    public void OnCreate(ref SystemState state)
    {
        var entity = state.EntityManager.CreateEntity();
        state.EntityManager.AddComponent<Rotation>(entity);

        // Get the Rotation component
        var rotationComponent = state.EntityManager.GetComponentData<Rotation>(entity);
    }
}
```

--------------------------------

### OnCreate()

Source: https://docs.unity3d.com/Packages/com.unity.entities%401.4/api/Unity.Entities.EndInitializationEntityCommandBufferSystem.html

The OnCreate() method initializes the EndInitializationEntityCommandBufferSystem instance.

```APIDOC
## OnCreate()

### Description
Initializes this command buffer system.

### Method
OnCreate()

### Parameters
None

### Return
void
```

--------------------------------

### Using Job.WithCode to schedule jobs

Source: https://docs.unity3d.com/Packages/com.unity.entities%401.4/api/Unity.Entities.SystemBase.Job.html

Example of a SystemBase class that uses Job.WithCode to generate random numbers and sum them. It schedules two jobs and completes dependencies to get the result immediately.

```csharp
public partial class RandomSumJob : SystemBase
{
    private uint seed = 1;
protected override void OnUpdate()
{
    Random randomGen = new Random(seed++);
    NativeArray<float> randomNumbers
        = new NativeArray<float>(500, Allocator.TempJob);

    Job.WithCode(() =>
    {
        for (int i = 0; i < randomNumbers.Length; i++)
        {
            randomNumbers[i] = randomGen.NextFloat();
        }
    }).Schedule();

    // To get data out of a job, you must use a NativeArray
    // even if there is only one value
    NativeArray<float> result
        = new NativeArray<float>(1, Allocator.TempJob);

    Job.WithCode(() =>
    {
        for (int i = 0; i < randomNumbers.Length; i++)
        {
            result[0] += randomNumbers[i];
        }
    }).Schedule();

    // This completes the scheduled jobs to get the result immediately, but for
    // better efficiency you should schedule jobs early in the frame with one
    // system and get the results late in the frame with a different system.
    this.CompleteDependency();
    UnityEngine.Debug.Log("The sum of "
        + randomNumbers.Length + " numbers is " + result[0]);

    randomNumbers.Dispose();
    result.Dispose();
}

}
```

--------------------------------

### Create and schedule an EntityCommandBuffer with EntityCommandBufferSystem

Source: https://docs.unity3d.com/Packages/com.unity.entities%401.4/manual/systems-entity-command-buffer-automatic-playback.html

Shows how to get the singleton of an EntityCommandBufferSystem, create an EntityCommandBuffer, and schedule an IJobEntity that records commands. The system automatically completes the job and plays back and disposes the ECB.

```csharp
// ... in a system.

// Assume an EntityCommandBufferSystem exists named FooECBSystem.
// This call to GetSingleton automatically registers the job so that
// it gets completed by the ECB system.
var singleton = SystemAPI.GetSingleton<FooECBSystem.Singleton>();

// Create a command buffer that will be played back
// and disposed by MyECBSystem.
EntityCommandBuffer ecb = singleton.CreateCommandBuffer(state.WorldUnmanaged);

// An IJobEntity with no argument to Schedule implicitly
// assigns its returned JobHandle to this.Dependency
new MyParallelRecordingJob() { ecbParallel = ecb.AsParallelWriter() }.Schedule();
```

--------------------------------

### Schedule UpdateOnChangeJob with LastSystemVersion assignment

Source: https://docs.unity3d.com/Packages/com.unity.entities%401.4/manual/iterating-data-ijobchunk-implement.html

System that assigns the job's LastSystemVersion and component type handles, then schedules the UpdateOnChangeJob in parallel. The query is built in OnCreate with the same change filter setup as the earlier example.

```csharp
[RequireMatchingQueriesForUpdate]
public partial class UpdateDataOnChangeSystem : SystemBase {

    EntityQuery query;

    protected override void OnUpdate()
    {
        var job = new UpdateOnChangeJob();

        job.LastSystemVersion = this.LastSystemVersion;

        job.InputATypeHandle = GetComponentTypeHandle<InputA>(true);
        job.InputBTypeHandle = GetComponentTypeHandle<InputB>(true);
        job.OutputTypeHandle = GetComponentTypeHandle<Output>(false);

        this.Dependency = job.ScheduleParallel(query, this.Dependency);
    }

    protected override void OnCreate()
    {
        query = new EntityQueryBuilder(Allocator.Temp)
            .WithAllRW<Output>()
            .WithAll<InputA, InputB>()
            .Build(this);
    }
}
```

--------------------------------

### SystemBase example to access all dynamic buffers in a chunk

Source: https://docs.unity3d.com/Packages/com.unity.entities%401.4/manual/components-buffer-get-all-in-chunk.html

Shows a SystemBase that queries for chunks with ExampleBufferComponent, converts them to ArchetypeChunk array, and iterates over each chunk to access and iterate through the dynamic buffers using GetBufferTypeHandle and GetBufferAccessorRW.

```csharp
public partial class ExampleSystem : SystemBase
{
    protected override void OnUpdate()
    {
        var query = new EntityQueryBuilder(Allocator.Temp)
            .WithAllRW<ExampleBufferComponent>()
            .Build(EntityManager);
        NativeArray<ArchetypeChunk> chunks = query.ToArchetypeChunkArray(Allocator.Temp);
        for (int i = 0; i < chunks.Length; i++)
        {
            UpdateChunk(chunks[i]);
        }
    }

    private void UpdateChunk(ArchetypeChunk chunk)
    {
        // Get a BufferTypeHandle representing dynamic buffer type ExampleBufferComponent from SystemBase.
        BufferTypeHandle<ExampleBufferComponent> myElementHandle = GetBufferTypeHandle<ExampleBufferComponent>();
        // Get a BufferAccessor from the chunk.
        BufferAccessor<ExampleBufferComponent> buffers = chunk.GetBufferAccessorRW(ref myElementHandle);
        // Iterate through all ExampleBufferComponent buffers of each entity in the chunk.
        for (int i = 0, chunkEntityCount = chunk.Count; i < chunkEntityCount; i++)
        {
            DynamicBuffer<ExampleBufferComponent> buffer = buffers[i];
            // Iterate through all elements of the buffer.
            for (int j = 0; j < buffer.Length; j++)
            {
                // ...
            }
        }
    }
}
```

--------------------------------

### Enable/disable with EnabledMask in IJobChunk

Source: https://docs.unity3d.com/Packages/com.unity.entities%401.4/manual/components-enableable-use.html

Use EnabledMask in IJobChunk to enable and disable components on entities in the current chunk. Get it with ArchetypeChunk.GetEnabledMask<T>() and use its indexer with the entity index from ChunkEntityEnumerator. Example disables AliveTag when Health is zero or less.

```csharp
public struct EnableAliveFromHealthChunkJob : IJobChunk
{
    [ReadOnly] public ComponentTypeHandle<Health> HealthTypeHandle;
    public ComponentTypeHandle<AliveTag> AliveTagTypeHandle;

    public void Execute(in ArchetypeChunk chunk, int unfilteredChunkIndex, bool useEnabledMask, in v128 chunkEnabledMask)
    {
        NativeArray<Health> chunkHealthValues = chunk.GetNativeArray(ref HealthTypeHandle);
        EnabledMask chunkAliveEnabledMask = chunk.GetEnabledMask(ref AliveTagTypeHandle);
        ChunkEntityEnumerator enumerator = new ChunkEntityEnumerator(useEnabledMask, chunkEnabledMask, chunk.Count);
        while(enumerator.NextEntityIndex(out var i))
        {
            // Disable the AliveTag component based on the Health component value.
            if (chunkHealthValues[i].Value <= 0)
                chunkAliveEnabledMask[i] = false;
        }
    }
}

```

--------------------------------

### Initialize(string, string, string, Action<ContentUpdateState>)

Source: https://docs.unity3d.com/Packages/com.unity.entities%401.4/api/Unity.Entities.Content.ContentDeliveryGlobalState.Initialize.html

Initializes the content delivery system with the specified remote URL root, cache path, initial content set, and update state callback.

```APIDOC
## Initialize(string, string, string, Action<ContentUpdateState>)

### Description
Initializes the content delivery system. This method sets up the remote URL root, local cache path, initial content set to download, and a callback that is invoked whenever the content update state changes.

### Method
`public static void Initialize(string remoteUrlRoot, string cachePath, string initialContentSet, Action<ContentDeliveryGlobalState.ContentUpdateState> updateStateFunc)`

### Parameters
- **remoteUrlRoot** (string) - The remote url root in the form of "https://hostname.com/pathToContent/". If this parameter is not specified, content is assumed to be local.
- **cachePath** (string) - The full local path of the content cache. This must be a directory that the application has read and write access to.
- **initialContentSet** (string) - The initial set of content to download. The content sets are given names during the publish process and by default everything is added to the "all" set.
- **updateStateFunc** (Action<ContentDeliveryGlobalState.ContentUpdateState>) - Callback action that will get called whenever the content update state changes.
```

--------------------------------

### ParentSystem.OnCreate(ref SystemState)

Source: https://docs.unity3d.com/Packages/com.unity.entities%401.4/api/Unity.Transforms.ParentSystem.html

Called when the system is created. Initializes the system state.

```APIDOC
## OnCreate(ref SystemState)

### Description
Called when the system is created. Initializes the system state.

### Method
OnCreate

### Parameters
- **state** (SystemState) - The system state.

### Remarks
This method is part of the ISystem interface and is called once when the system is created.
```

--------------------------------

### Shared component filtering with WithSharedComponentFilter<Cohort>

Source: https://docs.unity3d.com/Packages/com.unity.entities%401.4/manual/iterating-entities-foreach-filtering.html

Selects entities grouped by a shared component value using WithSharedComponentFilter. The example gets all unique Cohort values via EntityManager.GetAllUniqueSharedComponents, then schedules a lambda job for each cohort, passing the new color as a captured variable. Requires RequireMatchingQueriesForUpdate on the system.

```csharp
[RequireMatchingQueriesForUpdate]
public partial class ColorCycleJob : SystemBase
{
    protected unsafe override void OnUpdate()
    {

        EntityManager.GetAllUniqueSharedComponents<Cohort>(out var cohorts, Allocator.Temp);
        for (int i=0; i<cohorts.Length; i++)
        {
            var cohort = cohorts[i];
            DisplayColor newColor = ColorTable.GetNextColor(cohort.Value);
            Entities.WithSharedComponentFilter(cohort)
                .ForEach((ref DisplayColor color) => { color = newColor; })
                .ScheduleParallel();
        }
    }
}
```

--------------------------------

### Clear() usage example

Source: https://docs.unity3d.com/Packages/com.unity.entities%401.4/api/Unity.Entities.DynamicBuffer-1.Clear.html

An example of calling Clear() on a buffer.

```csharp
buffer.Clear();
```

--------------------------------

### OnCreate()

Source: https://docs.unity3d.com/Packages/com.unity.entities%401.4/api/Unity.Entities.BeginFixedStepSimulationEntityCommandBufferSystem.OnCreate.html

Initializes this command buffer system. This method is a protected override of EntityCommandBufferSystem.OnCreate(). If overridden, call base.OnCreate() to retain default initialization logic.

```APIDOC
## OnCreate()

### Description
Initializes this command buffer system.

### Declaration
```
protected override void OnCreate()
```

### Overrides
EntityCommandBufferSystem.OnCreate()

### Remarks
If you override this method, you should call `base.OnCreate()` to retain the default initialization logic.

```

--------------------------------

### SimpleBaker example: creating components and additional entities

Source: https://docs.unity3d.com/Packages/com.unity.entities%401.4/manual/baking-baker-overview.html

Shows a baker that inherits from Baker<RotationSpeedAuthoring> and adds a RotationSpeed component to the primary entity and Additional components to two additional entities. The authoring component must follow MonoBehaviour conventions and be in a file named RotationSpeedAuthoring.cs.

```csharp
// This RotationSpeedAuthoring class must follow the MonoBehaviour convention
// and should live in a file named RotationSpeedAuthoring.cs
public class RotationSpeedAuthoring : MonoBehaviour
{
    public float DegreesPerSecond;
}

public struct RotationSpeed : IComponentData
{
    public float RadiansPerSecond;
}

public struct Additional : IComponentData
{
    public float SomeValue;
}

public class SimpleBaker : Baker<RotationSpeedAuthoring>
{
    public override void Bake(RotationSpeedAuthoring authoring)
    {
        var entity = GetEntity(TransformUsageFlags.Dynamic);
        AddComponent(entity, new RotationSpeed
        {
            RadiansPerSecond = math.radians(authoring.DegreesPerSecond)
        });

        var additionalA = CreateAdditionalEntity(TransformUsageFlags.Dynamic, entityName: "Additional A");
        var additionalB = CreateAdditionalEntity(TransformUsageFlags.Dynamic, entityName: "Additional B");

        AddComponent(additionalA, new Additional { SomeValue = 123 });
        AddComponent(additionalB, new Additional { SomeValue = 234 });
    }
}
```

--------------------------------

### Copy from NativeArray Example

Source: https://docs.unity3d.com/Packages/com.unity.entities%401.4/api/Unity.Entities.DynamicBuffer-1.CopyFrom.html

Example for the CopyFrom(NativeArray<T>) overload. It creates a NativeArray<int> from an int[] source and copies its elements into the dynamic buffer. The example uses Allocator.Persistent for allocation.

```csharp
int[] sourceArray = { 1, 2, 3, 4, 5 };
NativeArray<int> nativeArray = new NativeArray<int>(source, Allocator.Persistent);
buffer.CopyFrom(nativeArray);
```

--------------------------------

### OnStartRunning(ref SystemState)

Source: https://docs.unity3d.com/Packages/com.unity.entities%401.4/api/Unity.Scenes.SceneSystem.OnStartRunning.html

Callback invoked when the system starts running. This method is part of the ISystemStartStop interface and is called by the system lifecycle.

```APIDOC
## OnStartRunning(ref SystemState)

### Description
Callback invoked when the system starts running.

### Method
OnStartRunning

### Declaration
public void OnStartRunning(ref SystemState state)

### Parameters
- **state** (SystemState) - The entity system state.

### Implements
ISystemStartStop.OnStartRunning(ref SystemState)
```
Tokens:
Raw