# DocumentBaseBox A Box that allows setting its Document base not requiring the caller to know the exact types of the box and its base. ``` protocol DocumentBaseBox : AnyObject ``` ## Topics ### Specifying the document type [`associatedtype Document`](/documentation/SwiftUI/DocumentBaseBox/Document) The underlying document type. ### Accessing the document [`var base: Self.Document?`](/documentation/SwiftUI/DocumentBaseBox/base) Updates the underlying document to a new value. --- 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)