# transform(updating:body:) Tracks the location of the provided ranges throughout the mutation closure, returning a new, updated range that represents the same effective locations after the mutation ``` mutating func transform(updating ranges: [Range], body: (inout AttributedString) throws(E) -> Void) throws(E) -> [Range]? where E : Error ``` ## Parameters `ranges` Ranges to track throughout the `body` block. `body` A mutating operation, or set of operations, to perform on this `AttributedString`. ## Return Value the updated `Range`s that are valid after the mutation has been performed or `nil` if the mutation performed does not allow for tracking to succeed (such as replacing the provided inout variable with an entirely different `AttributedString`). When the return value is non-`nil`, the returned array is guaranteed to be the same size as the provided array with updated ranges at the same indices as their respective original ranges in the input array. --- 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)