# init(_:) Creates an evaluator with the given evaluation closure. ``` init(_ evaluate: nonisolated(nonsending) @escaping (Input, ModelSubject) async throws -> Metric) ``` ## Parameters `evaluate` A closure that receives the input and subject, and returns a [`Metric`](/documentation/Evaluations/Metric) with a result value. ## Discussion ```swift let metric = Metric("ExactMatch") let evaluator = Evaluator> { sample, subject in guard let expected = sample.expected else { return metric.ignore() } return subject.value == expected ? metric.passing() : metric.failing() } ``` --- 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)