# init(historyTokens:observedModels:authors:modelContainer:isolation:) Creates a history observer that reports changes through its observable [`eventCounter`](/documentation/SwiftData/HistoryObserver/eventCounter) property. ``` convenience init(historyTokens: [String : any HistoryToken]? = nil, observedModels: [any PersistentModel.Type] = [], authors: Set = [], modelContainer: ModelContainer, isolation: isolated (any Actor)? = #isolation) throws ``` ## Parameters `historyTokens` The initial history tokens keyed by store identifier. When `nil`, the observer captures the current position for each store immediately, so that only transactions from this point forward are reported. `observedModels` The model types to filter for. When empty (the default), the observer responds to changes for any model. `authors` The transaction authors to filter for. When empty (the default), the observer responds to changes from any author. `modelContainer` The model container to observe. ## Discussion Use this initializer when you want to observe history changes via SwiftUI’s observation system or by reading [`eventCounter`](/documentation/SwiftData/HistoryObserver/eventCounter) directly. > Throws: An error if the observer fails to fetch the initial history tokens. --- 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)