# World > Encapsulates a set of entities, component data, and systems. ## Definition * **Type:** Class * **Namespace:** [Unity.Entities](/engine/7000.0/script-reference/unity/entities.md) * **Assembly:** UnityEngine.EntitiesModule * **Implements:** [IDisposable](https://learn.microsoft.com/dotnet/api/system.idisposable) ```csharp public class World : IDisposable ``` ## Remarks Multiple Worlds may exist concurrently in the same application, but they are isolated from each other; an [EntityQuery](/engine/7000.0/script-reference/unity/entities/entityquery.md) will only match entities in the World that created the query, a World's EntityManager can only process entities from the same World, etc. ## Constructors | Constructor | Description | | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ | ------------------------------ | | [World(System.String,Unity.Entities.WorldFlags)](/engine/7000.0/script-reference/unity/entities/world/ctor.md#world\(string-worldflags\)) | Construct a new World instance | | [World(System.String,Unity.Entities.WorldFlags,Unity.Collections.AllocatorManager.AllocatorHandle)](/engine/7000.0/script-reference/unity/entities/world/ctor.md#world\(string-worldflags-allocatorhandle\)) | Construct a new World instance | ## Properties | Property | Description | | ------------------------------------------------------------------------------------------------------------------------ | ----------------------------------------------------------------------------------------------------------------------------------- | | [CurrentGroupAllocators](/engine/7000.0/script-reference/unity/entities/world/currentgroupallocators.md) | Retrieve current double rewindable allocator for this World. | | [QuitUpdate](/engine/7000.0/script-reference/unity/entities/world/quitupdate.md) | Set this property to true to abort a world update after the next system update. | | [Systems](/engine/7000.0/script-reference/unity/entities/world/systems.md) | List of all managed systems in this World | | [TimeSingleton](/engine/7000.0/script-reference/unity/entities/world/timesingleton.md) | Singleton instance of the WorldTime component. This data is generally accessed through Time. | | [Unmanaged](/engine/7000.0/script-reference/unity/entities/world/unmanaged.md) | Gives access to the unmanaged data of an instance of the World. This is useful when your code needs to run with Burst. | | [UpdateAllocatorEnableBlockFree](/engine/7000.0/script-reference/unity/entities/world/updateallocatorenableblockfree.md) | Property to get and set enable block free flag, a flag indicating whether the allocator should enable individual block to be freed. | ## Static Properties | Property | Description | | -------------------------------------------------------------------------------------------------------------------------- | ------------------------------------------------------------------------------------------------------------------------------------------------------- | | [All](/engine/7000.0/script-reference/unity/entities/world/all.md) | List of all Worlds that currently exist in the application | | [DefaultGameObjectInjectionWorld](/engine/7000.0/script-reference/unity/entities/world/defaultgameobjectinjectionworld.md) | The default [World](/engine/7000.0/script-reference/unity/entities/world.md). The code that runs outside a system reads this property to reach a world. | ## Methods | Method | Description | | ------------------------------------------------------------------------------------------------------------------------------ | --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | | [AddSystemManaged](/engine/7000.0/script-reference/unity/entities/world/addsystemmanaged.md) | Adds an existing system instance to this World | | [CreateSystem](/engine/7000.0/script-reference/unity/entities/world/createsystem.md) | Create and return a handle to an instance of a system of type `type` in this World. | | [CreateSystemManaged](/engine/7000.0/script-reference/unity/entities/world/createsystemmanaged.md) | Create and return an instance of a system of type `type` in this World. | | [DestroyAllSystemsAndLogException](/engine/7000.0/script-reference/unity/entities/world/destroyallsystemsandlogexception.md) | Destroy all system instances in the World. Any errors encountered during individual system destruction will be logged to the console. | | [DestroySystem](/engine/7000.0/script-reference/unity/entities/world/destroysystem.md) | Destroys one of the World's existing system instances. | | [DestroySystemManaged](/engine/7000.0/script-reference/unity/entities/world/destroysystemmanaged.md) | Destroys one of the World's existing system instances. | | [Dispose](/engine/7000.0/script-reference/unity/entities/world/dispose.md) | Dispose of a World instance | | [GetExistingSystem](/engine/7000.0/script-reference/unity/entities/world/getexistingsystem.md) | Return a handle to an existing instance of a system of type `type` in this World. Prefer the version that takes a SystemTypeIndex where possible to avoid unnecessary reflection. | | [GetExistingSystemManaged](/engine/7000.0/script-reference/unity/entities/world/getexistingsystemmanaged.md) | Return an existing instance of a system of type `type` in this World. Prefer the version that takes a SystemTypeIndex where possible to avoid unnecessary reflection. | | [GetOrCreateSystem](/engine/7000.0/script-reference/unity/entities/world/getorcreatesystem.md) | Retrieve the handle for the instance of a system of type `type` from the current World. If the system does not exist in this World, it will first be created. | | [GetOrCreateSystemManaged](/engine/7000.0/script-reference/unity/entities/world/getorcreatesystemmanaged.md) | Retrieve the instance of a system of type `type` from the current World. If the system does not exist in this World, it will first be created. | | [GetOrCreateSystemsAndLogException](/engine/7000.0/script-reference/unity/entities/world/getorcreatesystemsandlogexception.md) | Creates systems from the list of types which aren't already created in the current world. | | [PopTime](/engine/7000.0/script-reference/unity/entities/world/poptime.md) | Restore the previous World time, after pushing a temporary time value with [World.PushTime](/engine/7000.0/script-reference/unity/entities/world/pushtime.md) | | [PushTime](/engine/7000.0/script-reference/unity/entities/world/pushtime.md) | Push a new temporary time value to the World's current time | | [RestoreGroupAllocator](/engine/7000.0/script-reference/unity/entities/world/restoregroupallocator.md) | Pop group allocator out of the stack. | | [SetGroupAllocator](/engine/7000.0/script-reference/unity/entities/world/setgroupallocator.md) | Push group allocator into a stack. | | [SetTime](/engine/7000.0/script-reference/unity/entities/world/settime.md) | Assigns a new value to the World's current time. | | [ToString](/engine/7000.0/script-reference/unity/entities/world/tostring.md) | Returns the name of the World | | [Update](/engine/7000.0/script-reference/unity/entities/world/update.md) | Update the World's default system groups. | ## Static Methods | Method | Description | | -------------------------------------------------------------------------------------------- | ---------------------------- | | [DisposeAllWorlds](/engine/7000.0/script-reference/unity/entities/world/disposeallworlds.md) | Destroys all existing Worlds | ## Structs | Struct | Description | | ------------------------------------------------------------------------------------------------------------------------- | -------------------------------------------------------------------------- | | [World.NoAllocReadOnlyCollection\](/engine/7000.0/script-reference/unity/entities/world/noallocreadonlycollection1.md) | Read only collection that doesn't generate garbage when used in a foreach. |