# withUnsafeMutableBytes(_:) Calls a given closure with a raw pointer to the multiarray’s mutable storage. ``` func withUnsafeMutableBytes(_ body: (UnsafeMutableRawBufferPointer, [Int]) throws -> R) rethrows -> R ``` ## Parameters `body` A closure with an parameter that points to the storage for the multiarray and its strides. This closure takes the following parameters: - `ptr`: The pointer to the buffer. - `strides`: The strides of the buffer in scalars. Note that this may be different from `strides`’s value prior to this method invocation. ## 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. --- Copyright © 2026 Apple Inc. All rights reserved. | [Terms of Use](https://www.apple.com/legal/internet-services/terms/site.html) | [Privacy Policy](https://www.apple.com/privacy/privacy-policy)