# Evaluator A closure-based evaluator. ``` struct Evaluator where Input : SampleProtocol, Input.ExpectedValue : Decodable, Input.ExpectedValue : Encodable, Input.ExpectedValue : Sendable ``` ## Overview Use Evaluator to create inline evaluators without defining a custom type. The closure receives the input sample and the [`ModelSubject`](/documentation/Evaluations/ModelSubject), providing access to both .value and .transcript. ``` Evaluator { sample, subject in let metric = Metric("TitleMatch") 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)