# train(trainingData:annotationType:parameters:sessionParameters:) Begins an asynchronous object-detector training session. ``` static func train(trainingData: MLObjectDetector.DataSource, annotationType: MLObjectDetector.AnnotationType, parameters: MLObjectDetector.ModelParameters = ModelParameters(), sessionParameters: MLTrainingSessionParameters = __Defaults.sessionParameters) throws -> MLJob ``` ## Parameters `trainingData` The annotated images the task uses to train the object detector. `annotationType` The format your data source uses for its image annotations. `parameters` An [`MLObjectDetector.ModelParameters`](/documentation/CreateML/MLObjectDetector/ModelParameters-swift.struct) instance you use to set the model configuration settings for the training session. `sessionParameters` An [`MLTrainingSessionParameters`](/documentation/CreateML/MLTrainingSessionParameters) instance you use to configure the training session. ## Return Value An [`MLJob`](/documentation/CreateML/MLJob) that represents the object-detector training session. --- 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)