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# update(context:)

Updates entities up to once every scene update.

```
@MainActor @preconcurrency mutating func update(context: SceneUpdateContext)
```

## Parameters

`context`

The scene context for the scene to update.

## Discussion

RealityKit calls this method on all registered systems,
as often as the `updatingSystemWhen` parameter of
[`entities(matching:updatingSystemWhen:)`](/documentation/RealityKit/SceneUpdateContext/entities(matching:updatingSystemWhen:))
defines.

The `context` parameter contains a reference to the scene
that the [`System`](/documentation/RealityKit/System) is updating, along with the elapsed time
since RealityKit last called the update method for the same scene.
Use [`entities(matching:updatingSystemWhen:)`](/documentation/RealityKit/SceneUpdateContext/entities(matching:updatingSystemWhen:))
inside this method for the most optimized way to find the matching entities
for this [`System`](/documentation/RealityKit/System).

---

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