# SkeletonResource.JointBuilder A result builder for declaratively constructing the children of a joint. ``` @resultBuilder struct JointBuilder ``` ## Overview Inside the `Joint(_:restPoseTransform:children:)` closure, you can write any mix of: - **`Joint` literals** — each becomes one child of the parent joint. ```swift try Joint("root") { try Joint("spine") try Joint("hip") } // root.children == [spine, hip] ``` - **`[Joint]` values** — each element becomes a child of the parent joint, in array order, alongside any other declarations in the same closure body. Use this when the children are produced from runtime data (e.g. mapped from a flat array) rather than spelled out as literals. ```swift let kids: [Joint] = ... try Joint("root") { kids // every element of kids becomes a child of root } ``` Both forms can be mixed freely. Each `Joint` in any array can itself be a fully built subtree. ## Topics ### Building joints [`static func buildBlock([SkeletonResource.Joint]...) -> [SkeletonResource.Joint]`](/documentation/RealityKit/SkeletonResource/JointBuilder/buildBlock(_:)) Combines all joints declared in the closure body into the parent’s `children`. ### Type Methods [`static buildExpression(_:)`](/documentation/RealityKit/SkeletonResource/JointBuilder/buildExpression(_:)) Treats a single `Joint` value in the closure body as one child of the parent. --- 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)