# WorldExtensions

> Variants of World methods that support unmanaged systems ( ISystem s)

## Definition

* **Type:** Class
* **Namespace:** [Unity.Entities](/engine/7000.0/script-reference/unity/entities.md)
* **Assembly:** UnityEngine.EntitiesModule

```csharp
public static class WorldExtensions
```

## Static Methods

| Method                                                                                                   | Description                                                                                                                                               |
| -------------------------------------------------------------------------------------------------------- | --------------------------------------------------------------------------------------------------------------------------------------------------------- |
| [CreateSystem](/engine/7000.0/script-reference/unity/entities/worldextensions/createsystem.md)           | Create and return a handle for an instance of a system of type `T` in this World.                                                                         |
| [GetExistingSystem](/engine/7000.0/script-reference/unity/entities/worldextensions/getexistingsystem.md) | Return an existing handle for an instance of a system of type `T` in this World.                                                                          |
| [GetOrCreateSystem](/engine/7000.0/script-reference/unity/entities/worldextensions/getorcreatesystem.md) | Retrieve the handle for an instance of a system of type `T` from the current World. If the system does not exist in this World, it will first be created. |