# contains(_:) Publishes a Boolean value upon receiving an element equal to the argument. ``` func contains(_ output: Self.Output) -> Publishers.Contains ``` ## Parameters `output` An element to match against. ## Return Value A publisher that emits the Boolean value `true` when the upstream publisher emits a matching value. ## Discussion Use [`contains(_:)`](/documentation/Combine/Publisher/contains(_:)) to find the first element in an upstream that’s equal to the supplied argument. The contains publisher consumes all received elements until the upstream publisher produces a matching element. Upon finding the first match, it emits `true` and finishes normally. If the upstream finishes normally without producing a matching element, this publisher emits `false` and finishes. In the example below, the [`contains(_:)`](/documentation/Combine/Publisher/contains(_:)) operator emits `true` the first time it receives the value `5` from the `numbers.publisher`, and then finishes normally. ``` let numbers = [-1, 5, 10, 5] numbers.publisher .contains(5) .sink { print("\($0)") } // Prints: "true" ``` --- 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)