---
title: registerSystem()
framework: realitykit
role: symbol
role_heading: Type Method
path: realitykit/system/registersystem()
---

# registerSystem()

Registers a system with RealityKit.

## Declaration

```swift
@MainActor @preconcurrency static func registerSystem()
```

## Mentioned in

Implementing systems for entities in a scene

## Discussion

Discussion Calling this method informs RealityKit of a system of defined behavior for its scenes. RealityKit automatically creates an instance of all registered systems for every scene and calls every registered system’s update(context:) method on every scene update. If you call registerSystem() multiple times, RealityKit ignores additional calls after the first.