# next(isolation:) Produces the next element in the prefix sequence. ``` mutating func next(isolation actor: isolated (any Actor)?) async throws(AsyncPrefixSequence.Failure) -> Base.Element? ``` ## Discussion Until reaching the number of elements to include, this iterator calls `next(isolation:)` on its base iterator and passes through the result. After reaching the maximum number of elements, subsequent calls to `next(isolation:)` return `nil`. --- 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)