Swift Core Knowledge References : concurrency.md for async/await, actors, Sendable, structured tasks. interop.md for ObjC, C, and Rust (cinterop) bridging, Keychain, Secure Enclave. Deep Knowledge : Use with technology: . Optionals Use (Swift 5.7+) — implicit shadow shorter than . Value vs Reference Types | Kind | Semantics | Allocation | Use for | |---|---|---|---| | | Value (copied on assign/pass) | Stack (usually) | Models, lightweight data, thread-safe by default | | | Value | Stack | Discriminated unions, sealed states | | | Reference (shared identity) | Heap | Identity, inheritance, Obj…