---
title: "withUnsafeMutableBytes(_:)"
framework: coreml
role: symbol
role_heading: Instance Method
path: "coreml/mlmultiarray/withunsafemutablebytes(_:)"
---

# withUnsafeMutableBytes(_:)

Calls a given closure with a raw pointer to the multiarray’s mutable storage.

## Declaration

```swift
func withUnsafeMutableBytes<R>(_ body: (UnsafeMutableRawBufferPointer, [Int]) throws -> R) rethrows -> R
```

## Parameters

- `body`: A closure with an doc://com.apple.documentation/documentation/Swift/UnsafeMutableRawBufferPointer parameter that points to the storage for the multiarray and its strides. This closure takes the following parameters:

## Discussion

Discussion The buffer contains a collection of int32, float16, float32, or float64 values, depending on the multiarray’s data type. It may not store these scalar values contiguously; use strides to get the buffer layout.

## See Also

### Providing buffer access

- [withUnsafeBufferPointer(ofType:_:)](coreml/mlmultiarray/withunsafebufferpointer(oftype:_:).md)
- [withUnsafeBytes(_:)](coreml/mlmultiarray/withunsafebytes(_:).md)
- [withUnsafeMutableBufferPointer(ofType:_:)](coreml/mlmultiarray/withunsafemutablebufferpointer(oftype:_:).md)