# transform(updating:body:) Tracks the location of the provided range throughout the mutation closure, updating the provided range to one that represents the same effective locations after the mutation. ``` mutating func transform(updating range: inout Range, body: (inout AttributedString) throws(E) -> Void) throws(E) where E : Error ``` ## Parameters `range` A range to track throughout the `body` closure. `body` A mutating operation, or set of operations, to perform on the value of `self`. The value of `self` is provided to the closure as an `inout AttributedString` that the closure should mutate directly. Do not capture the value of `self` in the provided closure - the closure should mutate the provided `inout` copy. ## Discussion If updating the provided range is not possible (tracking failed) then this function will fatal error. Use the `Optional`-returning variants to provide custom fallback behavior. --- 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)