Swift Coding Standards

Authoritative for Swift work. The non-negotiables are inline below; each area has a reference with the full rules, rationale, and patterns — read the relevant reference before working in that area, and when reviewing code against it.

Non-negotiables (always apply)

Modern Swift — @Observable (+ @State in views), never ObservableObject/@Published/@StateObject except when bridging old code. Actors + await MainActor.run {} over DispatchQueue. async/await over completion handlers and Combine (adapters for legacy APIs). Views take data

• action callbacks, not ViewModel blobs. Typed throws where they help. SDK 27: @State is now a macro — for any post-SDK-update compile error in a view using @State ("used before being initialized", "invalid redeclaration of synthesized property", "extraneous argument label"), consult the swiftui-whats-new-27 skill before fixing; the obvious fix (reordering init assignments) is wrong.