swift

name	swift
description	Swift language skill covering SwiftUI, async/await, optionals, protocols, Codable, and SPM. Use when building Swift/iOS applications.
trigger	swift, swiftui, ios, swift async await, codable, swift protocols, swift generics, swift package manager, spm

swift

Core Concepts

• SwiftUI: @View structs compose declaratively, @State for local state, @Binding for parent-child, @StateObject/ObservableObject for model
• Struct vs Class: structs are value types (copy on write), classes are reference types (identity + inheritance)
• Optionals: T? with if let/guard let for safe unwrapping, nil coalescing (??), optional chaining
• Protocols + Generics: protocol defines interface, associatedtype for generic protocols, protocol-oriented programming

Async/Await

• async/await: structured concurrency with Task, TaskGroup for parallel work, async let for child tasks
• Actors: protect mutable state with actor isolation, nonisolated for safe synchronous access
• MainActor: dispatch UI updates to main thread, @MainActor attribute on types or methods

Serialization & Package Management

• Codable: Encodable + Decodable protocols, JSONEncoder/Decoder, custom CodingKeys for mapping
• SPM: Swift Package Manager, Package.swift manifest, binary/library targets, package dependencies
• Result Builders: @ViewBuilder for conditional views, @SceneBuilder for scenes, custom result builders

Common Patterns

• property wrappers (@Published, @AppStorage, @ScaledMetric, @FocusState)
• SwiftUI lifecycle (onAppear, onChange, task modifier for async work)
• MVVM architecture with ObservableObject and @Published