# filter(_:) Creates an asynchronous sequence that contains, in order, the elements of the base sequence that satisfy the given error-throwing predicate. ``` @preconcurrency func filter(_ isIncluded: @escaping @Sendable (Self.Element) async throws -> Bool) -> AsyncThrowingFilterSequence ``` ## Parameters `isIncluded` An error-throwing closure that takes an element of the asynchronous sequence as its argument and returns a Boolean value that indicates whether to include the element in the filtered sequence. ## Return Value An asynchronous sequence that contains, in order, the elements of the base sequence that satisfy the given predicate. If the predicate throws an error, the sequence contains only values produced prior to the error. ## Discussion In this example, an asynchronous sequence called `Counter` produces `Int` values from `1` to `10`. The `filter(_:)` method returns `true` for even values and `false` for odd values, thereby filtering out the odd values, but also throws an error for values divisible by 5: ``` do { let stream = Counter(howHigh: 10) .filter { if $0 % 5 == 0 { throw MyError() } return $0 % 2 == 0 } for try await number in stream { print(number, terminator: " ") } } catch { print("Error: \(error)") } // Prints "2 4 Error: MyError() " ``` --- 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)