<!--
{
  "availability" : [
    "iOS: 12.2.0 -",
    "iPadOS: 12.2.0 -",
    "macCatalyst: 12.2.0 -",
    "macOS: 10.14.4 -",
    "tvOS: 12.2.0 -",
    "visionOS: 1.0.0 -",
    "watchOS: 5.2.0 -"
  ],
  "documentType" : "symbol",
  "framework" : "Swift",
  "identifier" : "/documentation/Swift/MutableSpan/init(mutableBytes:)",
  "metadataVersion" : "0.1.0",
  "role" : "Initializer",
  "symbol" : {
    "kind" : "Initializer",
    "modules" : [
      "Swift"
    ],
    "preciseIdentifier" : "s:s11MutableSpanVss20ConvertibleFromBytesRzs0c2ToE0RzlE07mutableE0AByxGs0a3RawB0V_tcfc"
  },
  "title" : "init(mutableBytes:)"
}
-->

# init(mutableBytes:)

Convert a raw span to a typed span.

```
init(mutableBytes: consuming MutableRawSpan)
```

## Parameters

`mutableBytes`

A raw span to reinterpret as typed elements.

## Discussion

The `byteCount` of `mutableBytes` must be a multiple of `Element`’s stride,
and the starting address of `mutableBytes` must be well-aligned for
the type of `Element`. If either of these requirements is not met,
this initializer will trap at runtime.

---

Copyright &copy; 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)