---
title: "update(_:)"
framework: realitykit
role: symbol
role_heading: Instance Method
path: "realitykit/lowlevelinstancetransformresource/update(_:)"
---

# update(_:)

Provides partial read-write CPU access to the transform data.

## Declaration

```swift
final func update<R, E>(_ body: @_lifetime(0: copy 0) (inout MutableSpan<float4x4>) throws(E) -> R) throws(E) -> R where E : Error, R : ~Copyable
```

## Parameters

- `body`: A closure that receives a MutableSpan<float4x4> over the current transform data. The span is valid only for the duration of the closure.

## Discussion

Discussion Use update when you want to modify a subset of transforms without fully replacing the buffer contents.