A Swift Tour: Explore Swift’s features and design - WWDC24 - Videos - Apple Developer (2024)

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• 1:49 - Integer variables

  See Also

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  var x: Int = 1var y: Int = xx = 42y

• 3:04 - User struct

  struct User { let username: String var isVisible: Bool = true var friends: [String] = []}var alice = User(username: "alice")alice.friends = ["charlie"]var bruno = User(username: "bruno")bruno.friends = alice.friendsalice.friends.append("dash")bruno.friends

• 3:05 - User struct error handling

  struct User { let username: String var isVisible: Bool = true var friends: [String] = [] mutating func addFriend(username: String) throws { guard username != self.username else { throw SocialError.befriendingSelf } guard !friends.contains(username) else { throw SocialError.duplicateFriend(username: username) } friends.append(username) }}enum SocialError: Error { case befriendingSelf case duplicateFriend(username: String)}var alice = User(username: "alice")do { try alice.addFriend(username: "charlie") try alice.addFriend(username: "charlie")} catch { error}var allUsers = [ "alice": alice]func findUser(_ username: String) -> User? { allUsers[username]}if let charlie = findUser("charlie") { print("Found \(charlie)")} else { print("charlie not found")}let dash = findUser("dash")!

• 11:01 - SocialGraph package manifest

  // swift-tools-version: 6.0import PackageDescriptionlet package = Package( name: "SocialGraph", products: [ .library( name: "SocialGraph", targets: ["SocialGraph"]), ], dependencies: [ .package(url: "https://github.com/apple/swift-testing.git", branch: "main"), ], targets: [ .target( name: "SocialGraph"), .testTarget( name: "SocialGraphTests", dependencies: [ "SocialGraph", .product(name: "Testing", package: "swift-testing"), ]), ])

• 11:12 - User struct

  /// Represents a user in the social graph.public struct User: Equatable, Hashable { /// The user's username, which must be unique in the service. public let username: String /// Whether or not the user should be considered visible /// when performing queries. public var isVisible: Bool /// The usernames of the user's friends. public private(set) var friends: [String] public init( username: String, isVisible: Bool = true, friends: [String] = [] ) { self.username = username self.isVisible = isVisible self.friends = friends } /// Adds a username to the user's list of friends. Throws an /// error if the username cannot be added. public mutating func addFriend(username: String) throws { guard username != self.username else { throw SocialError.befriendingSelf } guard !friends.contains(username) else { throw SocialError.alreadyFriend(username: username) } friends.append(username) }}

• 12:36 - Classes

  class Pet { func speak() {}}class Cat: Pet { override func speak() { print("meow") } func purr() { print("purr") }}let pet: Pet = Cat()pet.speak()if let cat = pet as? Cat { cat.purr()}

• 12:59 - Automatic reference counting

  class Pet { var toy: Toy?}class Toy {}let toy = Toy()let pets = [Pet()]// Give toy to petsfor pet in pets { pet.toy = toy}// Take toy from petsfor pet in pets { pet.toy = nil}

• 13:26 - Reference cycles

  See Also

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  class Pet { weak var owner: Owner?}class Owner { var pets: [Pet]}

• 14:20 - Protocols

  protocol StringIdentifiable { var identifier: String { get }}extension User: StringIdentifiable { var identifier: String { username }}

• 15:21 - Common capabilities of Collections

  let string = "🥚🐣🐥🐓"for char in string { print(char)}// => "🥚" "🐣" "🐥" "🐓"print(string[string.startIndex])// => "🥚"

• 15:31 - Collection algorithms

  let numbers = [1, 4, 7, 10, 13]let numberStrings = numbers.map { number in String(number)}// => ["1", "4", "7", "10", "13"]let primeNumbers = numbers.filter { number in number.isPrime}// => [1, 7, 13]let sum = numbers.reduce(0) { partial, number in partial + number}// => 35

• 15:45 - Collection algorithms with anonymous parameters

  let numbers = [1, 4, 7, 10, 13]let numberStrings = numbers.map { String($0) }// => ["1", "4", "7", "10", "13"]let primeNumbers = numbers.filter { $0.isPrime }// => [1, 7, 13]let sum = numbers.reduce(0) { $0 + $1 }// => 35

• 16:13 - Friends of friends algorithm

  /// An in-memory store for users of the service.public class UserStore { var allUsers: [String: User] = [:]}extension UserStore { /// If the username maps to a User and that user is visible, /// returns the User. Returns nil otherwise. public func lookUpUser(_ username: String) -> User? { guard let user = allUsers[username], user.isVisible else { return nil } return user } /// If the username maps to a User and that user is visible, /// returns the User. Otherwise, throws an error. public func user(for username: String) throws -> User { guard let user = lookUpUser(username) else { throw SocialError.userNotFound(username: username) } return user } public func friendsOfFriends(_ username: String) throws -> [String] { let user = try user(for: username) let excluded = Set(user.friends + [username]) return user.friends .compactMap { lookUpUser($0) } // [String] -> [User] .flatMap { $0.friends } // [User] -> [String] .filter { !excluded.contains($0) } // drop excluded .uniqued() }}extension Collection where Element: Hashable { func uniqued() -> [Element] { let unique = Set(self) return Array(unique) }}

• 19:23 - async/await

  /// Makes a network request to download an image.func fetchUserAvatar(for username: String) async -> Image { // ...}let avatar = await fetchUserAvatar(for: "alice")

• 19:43 - Server

  import Hummingbirdimport SocialGraphlet router = Router()extension UserStore { static let shared = UserStore.makeSampleStore()}let app = Application( router: router, configuration: .init(address: .hostname("127.0.0.1", port: 8080)))print("Starting server...")try await app.runService()

• 20:20 - Data race example

  // Look up userlet user = allUsers[username]// Store new userallUsers[username] = user// UserStorevar allUsers: [String: User]

• 22:24 - Server with friendsOfFriends route

  import Hummingbirdimport SocialGraphlet router = Router()extension UserStore { static let shared = UserStore.makeSampleStore()}router.get("friendsOfFriends") { request, context -> [String] in let username = try request.queryArgument(for: "username") return try await UserStore.shared.friendsOfFriends(username)}let app = Application( router: router, configuration: .init(address: .hostname("127.0.0.1", port: 8080)))print("Starting server...")try await app.runService()

• 23:27 - Property wrappers

  struct FriendsOfFriends: AsyncParsableCommand { @Argument var username: String mutating func run() async throws { // ... }}

• 23:57 - SocialGraph command line client

  import ArgumentParserimport SocialGraph@mainstruct SocialGraphClient: AsyncParsableCommand { static let configuration = CommandConfiguration( abstract: "A utility for querying the social graph", subcommands: [ FriendsOfFriends.self, ])}struct FriendsOfFriends: AsyncParsableCommand { @Argument(help: "The username to look up friends of friends for") var username: String func run() async throws { var request = Request(command: "friendsOfFriends", returning: [String].self) request.arguments = ["username" : username] let result = try await request.get() print(result) }}

• 26:07 - Result builders

  import RegexBuilderlet dollarValueRegex = Regex { // Equivalent to "\$[0-9]+\.[0-9][0-9]" "$" OneOrMore(.digit) "." Repeat(.digit, count: 2)}

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