Instance MethodFoundationEssentials

transform(updating:body:)

iOS 26.0+ iPadOS 26.0+ Mac Catalyst 26.0+ macOS 26.0+ tvOS 26.0+ visionOS 26.0+ watchOS 26.0+

Tracks the location of the provided ranges throughout the mutation closure, updating them to new ranges that represent the same effective locations after the mutation.

mutating func transform<E>(updating ranges: inout [Range<AttributedString.Index>], body: (inout AttributedString) throws(E) -> Void) throws(E) where E : Error

Parameters

ranges: A list of ranges to track throughout the body closure. The updated array (after the function is called) is guaranteed to be the same size as the provided array. Updated ranges are located at the same indices as their respective original ranges in the input ranges array.
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 ranges is not possible (tracking failed) then this function will fatal error. Use the Optional-returning variants to provide custom fallback behavior.