# removeDuplicates(by:) Publishes only elements that don’t match the previous element, as evaluated by a provided closure. ``` func removeDuplicates(by predicate: @escaping (Self.Output, Self.Output) -> Bool) -> Publishers.RemoveDuplicates ``` ## Parameters `predicate` A closure to evaluate whether two elements are equivalent, for purposes of filtering. Return `true` from this closure to indicate that the second element is a duplicate of the first. ## Return Value A publisher that consumes — rather than publishes — duplicate elements. ## Discussion Use [`removeDuplicates(by:)`](/documentation/Combine/Publisher/removeDuplicates(by:)) to remove repeating elements from an upstream publisher based upon the evaluation of the current and previously published elements using a closure you provide. Use the [`removeDuplicates(by:)`](/documentation/Combine/Publisher/removeDuplicates(by:)) operator when comparing types that don’t themselves implement `Equatable`, or if you need to compare values differently than the type’s `Equatable` implementation. In the example below, the [`removeDuplicates(by:)`](/documentation/Combine/Publisher/removeDuplicates(by:)) functionality triggers when the `x` property of the current and previous elements are equal, otherwise the operator publishes the current `Point` to the downstream subscriber: ``` struct Point { let x: Int let y: Int } let points = [Point(x: 0, y: 0), Point(x: 0, y: 1), Point(x: 1, y: 1), Point(x: 2, y: 1)] cancellable = points.publisher .removeDuplicates { prev, current in // Considers points to be duplicate if the x coordinate // is equal, and ignores the y coordinate prev.x == current.x } .sink { print("\($0)", terminator: " ") } // Prints: Point(x: 0, y: 0) Point(x: 1, y: 1) Point(x: 2, y: 1) ``` --- 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)