# GetExistingSystem<T>(World)

> Return an existing handle for an instance of a system of type T in this World.

## Definition

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

```csharp
public static SystemHandle GetExistingSystem<T>(this World self) where T : unmanaged, ISystem
```

### Parameters

**** (\[World]\(/engine/7000.0/script-reference/unity/entities/world)): The World

### Returns

| Type                                                                           | Description                                                                                                                               |
| ------------------------------------------------------------------------------ | ----------------------------------------------------------------------------------------------------------------------------------------- |
| [SystemHandle](/engine/7000.0/script-reference/unity/entities/systemhandle.md) | The existing system instance's handle of system type `T` in this World. If no such instance exists, the method returns SystemHandle.Null. |