# Loader A protocol for types that supply a dataset for evaluation. ``` protocol Loader : Sendable ``` ## Overview Use one of the built-in concrete types such as [`ArrayLoader`](/documentation/Evaluations/ArrayLoader), [`JSONLoader`](/documentation/Evaluations/JSONLoader), or [`StreamLoader`](/documentation/Evaluations/StreamLoader), or implement this protocol directly for custom data sources. ```swift var dataset: any Loader> { ArrayLoader(samples: [ ModelSample(prompt: "One plus one is...", expected: "Two."), ModelSample(prompt: "Swift is...", expected: "A powerful language."), ]) } ``` ```swift var dataset: any Loader> { JSONLoader(url: Bundle.main.url(forResource: "prompts", withExtension: "jsonl")!) } ``` ```swift var dataset: any Loader> { StreamLoader(stream: AsyncThrowingStream, Error> { continuation in Task { let prompts = ["One plus one is...", "Swift is..."] for prompt in prompts { continuation.yield(ModelSample(prompt: prompt, expected: "")) } continuation.finish() } }) } ``` ## Topics ### Loaders [`ArrayLoader`](/documentation/Evaluations/ArrayLoader) A loader backed by an in-memory array. [`JSONLoader`](/documentation/Evaluations/JSONLoader) A loader backed by a JSON or JSONL file. [`StreamLoader`](/documentation/Evaluations/StreamLoader) A loader backed by a custom async sequence. ## Relationships ### Inherits From [`Sendable`](/documentation/Swift/Sendable) [`SendableMetatype`](/documentation/Swift/SendableMetatype) ### Conforming Types [`ArrayLoader`](/documentation/Evaluations/ArrayLoader) [`JSONLoader`](/documentation/Evaluations/JSONLoader) [`StreamLoader`](/documentation/Evaluations/StreamLoader) --- 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)