# filter(_:) Republishes all elements that match a provided closure. ``` func filter(_ isIncluded: @escaping (Self.Output) -> Bool) -> Publishers.Filter ``` ## Parameters `isIncluded` A closure that takes one element and returns a Boolean value indicating whether to republish the element. ## Return Value A publisher that republishes all elements that satisfy the closure. ## Discussion Combine’s [`filter(_:)`](/documentation/Combine/Publisher/filter(_:)) operator performs an operation similar to that of in the Swift Standard Library: it uses a closure to test each element to determine whether to republish the element to the downstream subscriber. The following example, uses a filter operation that receives an `Int` and only republishes a value if it’s even. ``` let numbers: [Int] = [1, 2, 3, 4, 5] cancellable = numbers.publisher .filter { $0 % 2 == 0 } .sink { print("\($0)", terminator: " ") } // Prints: "2 4" ``` --- 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)