ReferenceFileDocument

protocol · iOS 14.0+ · Deprecated in iOS 100000.0 · SDK 27.1

@preconcurrency protocol ReferenceFileDocument : ObservableObject, Sendable

A type that you use to serialize reference type documents to and from file. To store a document as a reference type --- like a class --- create a type that conforms to the `ReferenceFileDocument` protocol and implement the required methods and properties. Your implementation: * Provides a list of the content types that the document can read from and write to by defining ``readableContentTypes``. If the list of content types that the document can write to is different from those that it reads from, you can optionally also define ``writableContentTypes-6x6w9``. * Loads documents from file in the ``init(configuration:)`` initializer. * Stores documents to file by providing a snapshot of the document's content in the ``snapshot(contentType:)`` method, and then serializing that content in the ``fileWrapper(snapshot:configuration:)`` method. Because `ReferenceFileDocument` is a reference type, SwiftUI can't detect changes to your document's properties on its own. Register an undo action with the environment's `UndoManager` whenever you mutate the document, for example by calling ``UndoManager/registerUndo(withTarget:handler:)``. Ensure that types that conform to this protocol are ``Sendable``. In particular, SwiftUI calls the protocol's methods from different isolation domains. Don't perform serialization and deserialization on ``MainActor``. final class PDFDocument: ReferenceFileDocument { struct Storage { var contents: Data } static let readableContentTypes: [UTType] = [.pdf] let storage: Mutex<Storage> required init(configuration: ReadConfiguration) throws { guard let data = configuration.file.regularFileContents else { throw CocoaError(.fileReadCorruptFile) } self.storage = .init(.init(contents: data)) } func snapshot(contentType: UTType) throws -> Data { storage.withLock { $0.contents } } func fileWrapper(snapshot: Data, configuration: WriteConfiguration) throws -> FileWrapper { return FileWrapper(regularFileWithContents: snapshot) } } > Important: If you store your document as a value type --- like a structure --- use ``FileDocument`` instead. Because a value type's changes are always visible to SwiftUI, undo management and the registration of undo actions are automatic.

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