# init(_:id:content:) Creates an instance that uniquely identifies and creates slider ticks across updates based on the provided key path to the underlying data’s identifier. ``` nonisolated init(_ data: Data, id: KeyPath, @SliderTickBuilder content: @escaping (Data.Element) -> Content) where V == Data.Element, Data.Element == Content.Value ``` ## Parameters `data` The data that the [`ForEach`](/documentation/SwiftUI/ForEach) instance uses to create mark items dynamically. `id` The key path to the provided data’s identifier. `content` The builder that creates ticks dynamically. ## Discussion It’s important that the `id` of a data element doesn’t change, unless SwiftUI considers the data element to have been replaced with a new data element that has a new identity. If the `id` of a data element changes, then the marks generated from that data element will lose any current state and animations. --- 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)