api: YAML JSON TOON Database
version: 1.0.0
format: json
dataset:
  id: 51
  slug: swift-language-features
  title: Swift Language Features
  description: "Swift programming language features: optionals, protocol-oriented programming, generics, async/await, SwiftUI, and memory management (ARC)."
  summary: "Swift language features with the version they arrived, a description, syntax and notes: optionals, protocol-oriented programming, generics, result builders, async/await, actors, property wrappers and automatic reference counting."
  use_when[2]: You are learning Swift or reading SwiftUI-era code.,You need the Swift version in which a feature appeared.
  caveats[2]: Swift evolves quickly; confirm feature availability against the Xcode and Swift version you target.,Strict concurrency checking has been rolled out in stages and can change build behavior.
  related[4]: language-comparison-2026,csharp-dotnet-features,rust-language-features,behavioral-design-patterns
  category: Programming Languages
  category_slug: programming-languages
  tags: "swift,ios,optionals,protocols,generics,async-await,swiftui,arc"
  view_count: 0
  created_at: 1778695229
  updated_at: 1778695229
  entry_count: 8
  fields[5]{section,field,type,example}:
    features,name,string,Optionals
    features,introduced,string,Swift 1.0
    features,description,string,"Type-safe way to represent nil values: Optional…"
    features,syntax,string,"var name: String?; if let unwrapped = name { }"
    features,notes,string,Force unwrap (!) crashes on nil; use guard let …
data:
  features[8]{name,introduced,description,syntax,notes}:
    Optionals,Swift 1.0,"Type-safe way to represent nil values: Optional<T> enum with .none and .some(T)","var name: String?; if let unwrapped = name { }",Force unwrap (!) crashes on nil; use guard let for early exit
    Protocol-Oriented Programming,Swift 2.0,Define behavior via protocols with default implementations in extensions,"protocol Drawable { func draw() }; extension Drawable { func draw() { /* default */ } }",Prefer protocols over inheritance for flexibility and composition
    Generics,Swift 1.0,"Write flexible, reusable code with type parameters and constraints","func swap<T>(_ a: inout T, _ b: inout T) { (a, b) = (b, a) }","Use where clauses for complex constraints: func process<T: Equatable>(items: [T]) where T: Hashable"
    Result Builder,Swift 5.4,"DSL-like syntax for building values ( SwiftUI views, async let groups)","@resultBuilder struct HTMLBuilder { static func buildBlock(_ parts: String...) -> String { parts.joined() } }",Foundation of SwiftUI's declarative syntax
    async/await,Swift 5.5,"Structured concurrency with async functions, await keyword, and structured task groups","async func fetchData() async throws -> Data { try await URLSession.shared.data(from: url) }",Replaces callback-based patterns; integrates with actors for thread safety
    Actors,Swift 5.5,"Reference types with actor isolation: only one task accesses mutable state at a time","actor BankAccount { var balance: Double; func deposit(_ amount: Double) async { balance += amount } }",Prevents data races; await required when accessing from outside
    Property Wrappers,Swift 5.1,"Separate property storage logic from definition: @propertyWrapper struct","@propertyWrapper struct Lazy<T> { var value: T?; var wrappedValue: T { get set } }","Used by @State, @Binding, @ObservedObject in SwiftUI"
    ARC (Automatic Reference Counting),Swift 1.0,Memory management via reference counting; weak/unowned for breaking retain cycles,"weak var delegate: DelegateProtocol?; unowned let owner: Owner",No garbage collector; understand strong/weak/unowned to avoid leaks and crashes