# init(fetchDescriptor:sectionBy:modelContext:isolation:) Creates a new observer with the given fetch descriptor, an optional String section key path, and a model context. ``` convenience init(fetchDescriptor: FetchDescriptor = FetchDescriptor(), sectionBy: KeyPath, modelContext: ModelContext, isolation: isolated (any Actor)? = #isolation) throws ``` ## Parameters `fetchDescriptor` The descriptor defining the fetch criteria. `sectionBy` A key path on the element type that returns an optional section name. `modelContext` The model context to fetch from and observe for changes. ## Discussion Use this initializer when the section key path points to an optional `String` property. Elements whose section value is `nil` are grouped into a section with an empty name. > Throws: An error if the initial fetch fails. --- 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)