# PreprocessingSupervisedEstimator A supervised estimator that composes a preprocessing transformer and a supervised estimator. ``` struct PreprocessingSupervisedEstimator where Preprocessor : Transformer, Estimator : SupervisedEstimator, Preprocessor.Output == Estimator.Transformer.Input ``` ## Topics ### Creating the estimator [`init(Preprocessor, Estimator)`](/documentation/CreateMLComponents/PreprocessingSupervisedEstimator/init(_:_:)) Creates a composed supervised estimator from a preprocessing transformer and an estimator. ### Getting the properties [`var estimator: Estimator`](/documentation/CreateMLComponents/PreprocessingSupervisedEstimator/estimator) The estimator. [`var preprocessor: Preprocessor`](/documentation/CreateMLComponents/PreprocessingSupervisedEstimator/preprocessor) The preprocessing transformer. ### Preprocessing and fitting [`func preprocessed(from: S, eventHandler: EventHandler?) async throws -> AnySequence.Annotation>>`](/documentation/CreateMLComponents/PreprocessingSupervisedEstimator/preprocessed(from:eventHandler:)) Preprocesses a sequence of examples. [`func fitted(to: InputSequence, eventHandler: EventHandler?) async throws -> PreprocessingSupervisedEstimator.Transformer`](/documentation/CreateMLComponents/PreprocessingSupervisedEstimator/fitted(to:eventHandler:)) Fits a composed transformer to a sequence of examples. [`func fitted(toPreprocessed: S, eventHandler: EventHandler?) async throws -> PreprocessingSupervisedEstimator.Transformer`](/documentation/CreateMLComponents/PreprocessingSupervisedEstimator/fitted(toPreprocessed:eventHandler:)) Fits a transformer to a sequence of preprocessed features. [`func fitted(to: InputSequence, validateOn: Validation, eventHandler: EventHandler?) async throws -> PreprocessingSupervisedEstimator.Transformer`](/documentation/CreateMLComponents/PreprocessingSupervisedEstimator/fitted(to:validateOn:eventHandler:)) Fits a composed transformer to a sequence of examples. [`func fitted(toPreprocessed: Input, validateOn: Validation, eventHandler: EventHandler?) async throws -> PreprocessingSupervisedEstimator.Transformer`](/documentation/CreateMLComponents/PreprocessingSupervisedEstimator/fitted(toPreprocessed:validateOn:eventHandler:)) Fits a composed transformer to a sequence of preprocessed features. [`typealias Annotation`](/documentation/CreateMLComponents/PreprocessingSupervisedEstimator/Annotation) The annotation type. [`typealias Input`](/documentation/CreateMLComponents/PreprocessingSupervisedEstimator/Input) The input type. [`typealias Intermediate`](/documentation/CreateMLComponents/PreprocessingSupervisedEstimator/Intermediate) The intermediate type. [`typealias Output`](/documentation/CreateMLComponents/PreprocessingSupervisedEstimator/Output) The output type. [`protocol Transformer`](/documentation/CreateMLComponents/Transformer) A transformer that takes an input and produces an output. ## Relationships ### Conforms To [`Sendable`](/documentation/Swift/Sendable) [`SupervisedEstimator`](/documentation/CreateMLComponents/SupervisedEstimator) [`SendableMetatype`](/documentation/Swift/SendableMetatype) --- 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)