# prefix(_:) Returns an asynchronous sequence, up to the specified maximum length, containing the initial elements of the base asynchronous sequence. ``` func prefix(_ count: Int) -> AsyncPrefixSequence ``` ## Parameters `count` The maximum number of elements to return. The value of `count` must be greater than or equal to zero. ## Return Value An asynchronous sequence starting at the beginning of the base sequence with at most `count` elements. ## Discussion Use `prefix(_:)` to reduce the number of elements produced by the asynchronous sequence. In this example, an asynchronous sequence called `Counter` produces `Int` values from `1` to `10`. The `prefix(_:)` method causes the modified sequence to pass through the first six values, then end. ``` for await number in Counter(howHigh: 10).prefix(6) { print(number, terminator: " ") } // Prints "1 2 3 4 5 6 " ``` If the count passed to `prefix(_:)` exceeds the number of elements in the base sequence, the result contains all of the elements in the sequence. --- 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)