Swift Concurrency時代のiOSアプリの作り方

Swi$ Concurrency ࣌୅ͷ
iOS ΞϓϦͷ࡞Γํ
Yuta Koshizawa @koher

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͜ͷ਺೥ͷ iOS ΞϓϦ։ൃͷมԽ
• Swi%UI (2019)
• Combine (2019)
• Swi$ Concurrency (2021)

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Swi$ Concurrency ࣌୅ͷ iOS ΞϓϦ։ൃͷ
ϕʔεϥΠϯΛߟ͑Δࢀߟʹ

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ViewController ʹϕλॻ͖
↓
ViewModel Λಋೖ
↓
DI ͱςετ

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ViewController ʹϕλॻ͖

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LoginViewController
final class LoginViewController: UIViewController {
@IBOutlet private var idField: UITextField!
@IBOutlet private var passwordField: UITextField!
@IBOutlet private var loginButton: UIButton!
...

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LoginViewController
final class LoginViewController: UIViewController {
@IBOutlet private var idField: UITextField!
@IBOutlet private var passwordField: UITextField!
@IBOutlet private var loginButton: UIButton!
@IBAction private func loginButtonPressed(
sender: UIButton) {
...
}
...

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loginButtonPressed
sender: UIButton) {
// ͜͜ͰϩάΠϯͷ API Λୟ͘
}

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AuthAPI.logIn
enum AuthAPI {
static func logIn(
id: String,
password: String
) async throws -> String { // ID token
...
}
}

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AuthAPI.logIn
enum AuthAPI {
static func logIn(
for id: String,
with password: String
) async throws -> String { // ID token
...
}
}

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AuthAPI.logIn
enum AuthAPI {
static func logIn(
for id: User.ID,
) async throws -> IDToken {
...
}
}

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User.ID
struct User: Identifiable {
let id: String
var nickname: String
var birthday: Date
}

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User.ID
let id: ID
var birthday: Date
}

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User.ID
let id: ID
var birthday: Date
struct ID: Hashable {
let rawValue: String
init(rawValue: String) {
self.rawValue = rawValue
}
}
}

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User.ID
struct User: Identifiable, Sendable {
let id: ID
var birthday: Date
}
}
}

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Sendable
ฒߦʹѻͬͯ΋҆શͳܕͰ͋Δ͜ͱΛࣔ͢
• actor ڥքΛ௒͑Δͷʹඞཁ
• Task.init ͳͲ @Sendable ΫϩʔδϟʹΩϟϓνϟ͢Δͷ
ʹඞཁ

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User.ID
let id: ID
var birthday: Date
}
}
}

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User.ID
let id: ID
var birthday: Date
struct ID: Hashable, Sendable {
}
}
}

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!
ฒߦʹѻ͏ܕ͸ Sendable ʹ४ڌͤ͞Δ

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User.ID
let id: ID
var birthday: Date
struct ID: Hashable, Sendable {
}
}
}

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@unchecked Sendable
// Xcode 13 ·Ͱͷ৔߹
extension Date: @unchecked Sendable {}

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!
Sendable ରԠ͍ͯ͠ͳ͍ܕ͸
@unchecked Sendable Ͱ
ແཧ΍Γ४ڌͤ͞ΒΕΔ
※ Sendable ʹͯ͠΋҆શͳ৔߹͚ͩ

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Sendable ʹͯ͠΋҆શͳܕͷྫ
• ७ਮͳ struct
• ΠϛϡʔλϒϧΫϥε
• ϛϡʔλϒϧ͚ͩͲϩοΫ౳Ͱอޢ͞ΕͨΫϥε
• actor
• ɾɾɾ

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AuthAPI.logIn
enum AuthAPI {
static func logIn(
for id: User.ID,
...
}
}

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AuthAPI.logIn
static func logIn(...) async throws -> IDToken {
let url: URL = ...
let request: URLRequest = ...
// Concurrency Ҏલ
let dataTask = URLSession.shared
.dataTask(with: request) {
// ίʔϧόοΫͰ݁ՌΛड͚औΔ
}
...
}

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AuthAPI.logIn
let url: URL = ...
let request: URLRequest = ...
// Concurrency Ҏ߱
let (data, response) = try await URLSession.shared
.data(for: request) // ໭Γ஋Ͱ݁ՌΛड͚औΔ
...
}

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AuthAPI.logIn
let (data, response) = ...
let idToken: IDToken = ...
return idToken
}

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͢ͰʹίʔϧόοΫ൛͕͋Δ৔߹
enum AuthAPI {
static func logIn(
for id: User.ID,
with password: String,
completion: @escaping
(Result) -> Void
) {
...
}
}

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͢ͰʹίʔϧόοΫ൛͕͋Δ৔߹
extension AuthAPI {
static func logIn(
for id: User.ID,
try await withCheckedThrowingContinuation
{ continuation in
logIn(for: id, with: password) { result in
continuation.resume(with: result)
}
}
}

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!
Con%nua%on Λ࢖͑͹ίʔϧόοΫΛ
async ʹม׵Ͱ͖Δ

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loginButtonPressed
sender: UIButton) {
// ͜͜ͰϩάΠϯͷ API Λୟ͘
}

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loginButtonPressed
sender: UIButton) {
let idToken = try await AuthAPI.logIn( //
for: .init(rawValue: idField.text ?? ""),
with: passwordField.text ?? ""
)
...
}

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loginButtonPressed
sender: UIButton) {
Task { // async throws
)
...
}
}

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loginButtonPressed
sender: UIButton) {
Task.init { // async throws
)
...
}
}

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loginButtonPressed
sender: UIButton) {
)
...
}
}

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!
ಉظϝιου͔ΒඇಉظॲཧΛ
࢝ΊΔʹ͸ Task.init Λ࢖͏

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loginButtonPressed
sender: UIButton) {
)
...
}
}

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loginButtonPressed
sender: UIButton) {
do {
let idToken = try await AuthAPI.logIn(...)
...
} catch {
// ΤϥʔϋϯυϦϯά
}
}
}

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!
Task.init ʹ౉͢ΫϩʔδϟͰ͸
do/catch Λ๨Εͳ͍Α͏ʹ͢Δ

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loginButtonPressed
sender: UIButton) {
Task {
loginButton.isEnabled = false
defer { loginButton.isEnabled = true }
...
}
}

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loginButtonPressed
sender: UIButton) {
// main εϨου
Task {
// ???
...
}
}

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loginButtonPressed
sender: UIButton) {
// main εϨου
Task {
// main εϨου
...
}
}

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UIViewController ͱ @MainActor
@MainActor class UIViewController : UIResponder

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loginButtonPressed
@IBAction private func loginButtonPressed(...) {
// main εϨου
Task {
// main εϨου
do {
// main εϨου

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!
Task.init ͸ actor context ΛҾ͖ܧ͙

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!
UIViewController ͸ MainActor Ͱ
อޢ͞Ε͍ͯΔ

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loginButtonPressed
sender: UIButton) {
// main εϨου
Task {
// main εϨου
...
}
}

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Swi$ ͷόά
@MainActor ͳϝιουͰɺ Task.init ʹ౉͢Ϋϩʔδϟͷத
Ͱ defer ͢Δͱɺ MainActor Ͱอޢ͞Ε͍ͯͳ͍ͱ൑அ͞Εͯ
͠·͏ɻ
2021/08/01 ʹϑΥʔϥϜͰใࠂ Swi* Forums #50796 ͞Ε௕Β͘ղܾ͞
Ε͍ͯͳ͔͕ͬͨɺ 2022/08/22 ʹ PR apple/swi* #60688 ͕࡞ΒΕɺ
8/31 ʹϚʔδɻ
apple/swi) #60688 h0ps:/
/github.com/apple/swi)/pull/60688
Swi$ Forums #50796 h3ps:/
/forums.swi$.org/t/a-bug-cant-defer-actor-isolated-variable-access/50796

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loginButtonPressed
sender: UIButton) {
// main εϨου
Task {
// main εϨου
...
}
}

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MainActor Ͱ࣮ߦ͢Δํ๏
• await MainActor.run { }
• Task { @MainActor in ... }

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loginButtonPressed
sender: UIButton) {
// main εϨου
Task {
// main εϨου
...
}
}

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loginButtonPressed
sender: UIButton) {
// main εϨου
Task {
// main εϨου
defer {
Task {
await MainActor.run {
loginButton.isEnabled = true
}
}

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loginButtonPressed
sender: UIButton) {
// main εϨου
Task {
// main εϨου
defer {
Task { @MainActor in
}
}

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MainActor.run ͱ Task { @MainActor in }
func foo() async {
await MainActor.run {
// ϝΠϯεϨουͰ࣮ߦ͍ͨ͠ॲཧ
}
}
func bar() {
// ϝΠϯεϨουͰ࣮ߦ͍ͨ͠ॲཧ
}
}

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!
async ϝιου͔ΒҰ෦ͷॲཧΛ
ϝΠϯεϨουͰ࣮ߦ͍ͨ͠৔߹͸
await MainActor.run { }

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!
ಉظϝιου͔ΒϝΠϯεϨουʹ
ॲཧ౤͍͛ͨ৔߹ʹ͸
Task { @MainActor in }

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DispatchQueue.main.async ͸ʁ
@Sendable ͕෇͍͍ͯͳ͍ͷͰආ͚ͨํ͕ྑ͍ɻ
func async(
group: DispatchGroup? = nil,
qos: DispatchQoS = .unspecified,
flags: DispatchWorkItemFlags = [],
execute work: @escaping () -> Void
)

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loginButtonPressed
sender: UIButton) {
Task {
defer {
}
}
...
}

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loginButtonPressed
sender: UIButton) {
Task {
...
}
}

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loginButtonPressed
sender: UIButton) {
Task {
...
}

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loginButtonPressed
sender: UIButton) {
Task { ...
do {
...
} catch {
// ΤϥʔϋϯυϦϯά
}
}
}

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loginButtonPressed
sender: UIButton) {
Task { ...
do {
let data: Data = idToken.rawValue
.data(using: .utf8)!
let url: URL = .libraryDirectory
.appendingPathComponent("IDToken")
try data.write(to: url, options: .atomic)
...

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Task.detached
Task.detached {
let data: Data = idToken.rawValue
}

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!
ॏΊͷॲཧ͸ Task.detached Ͱ
ผεϨουʹಀ͢

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loginButtonPressed
sender: UIButton) {
Task { ...
do {
Task.detached {
...
try data.write(to: url,
options: .atomic)
}
...

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loginButtonPressed
sender: UIButton) {
Task { ...
do {
_ = try await Task.detached {
...
try data.write(to: url,
options: .atomic)
}.value
...

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!
ޙଓॲཧ͕͋Δ৔߹͸
Task.detached ͔Β
value Λऔಘͯ͠
ॲཧ͕ऴΘΔͷΛ଴ͭ

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Task.detached ΑΓ
΋ͬͱྑ͍ํ๏͕͋Δ

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actor
actor IDTokenStore {
func update(_ value: IDToken) throws {
let data: Data = value.rawValue
}
}

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actor
var value: IDToken {
get throws {
let data: Data = try .init(contentsOf: url)
let rawValue: String =
.init(data: data, encoding: .utf8)!
return IDToken(rawValue: rawValue)
}
}
...

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!
ഉଞతʹ࣮ߦ͍ͨ͠ॲཧ͸ actor Ͱอޢ

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actor
static let shared: IDTokenStore = .init()
private init() {}
...
}

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!
actor ͸Πϯελϯε͝ͱʹ
Serial Executor Λ࣋ͪอޢ͞ΕΔ
※ άϩʔόϧʹอޢ͍ͨ͠ͳΒγϯάϧτϯʹ͢Δ

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loginButtonPressed
sender: UIButton) {
Task { ...
do {
try await IDTokenStore.shared
.update(idToken)
...

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actor ͷϝιου͸֎͔ΒݟΔͱ async ʹͳΔ
func update(_ value: IDToken) throws {
let data: Data = value.rawValue
}
}

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loginButtonPressed
sender: UIButton) {
Task { ...
do {
.update(idToken)
...

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AuthService
actor AuthService {
func logIn(
for id: User.ID,
) async throws {
...
}
}

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AuthService
actor AuthService {
func logIn(
for id: User.ID,
) async throws {
let idToken = try await AuthAPI
.logIn(for: id, with: password)
.update(idToken)
}
}

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A B
AuthAPI.login (1) (2)
IDTokenStore.sh
ared.update
(4) (3)

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AuthService
actor AuthService {
func logIn(
for id: User.ID,
) async throws {
.update(idToken)
}
}

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AuthService
actor AuthService {
private var isLoggingIn: Bool = false
func logIn(
for id: User.ID,
) async throws {
.update(idToken)
}

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AuthService
actor AuthService {
private var isLoggingIn: Bool = false
func logIn(
for id: User.ID,
) async throws {
if isLoggingIn { ... }
isLoggingIn = true
defer { isLoggingIn = false}
...
}

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loginButtonPressed
sender: UIButton) {
Task { ...
do {
.update(idToken)
...

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loginButtonPressed
sender: UIButton) {
Task { ...
do {
try await AuthService.shared.logIn(...)
...

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loginButtonPressed
sender: UIButton) {
Task { ...
do {
parent?.dismiss(animated: true)
} catch {
...

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loginButtonPressed
sender: UIButton) {
Task { ...
do { ... } catch {
logger.warning("\(error)")
...

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loginButtonPressed
sender: UIButton) {
Task { ...
do { ... } catch {
...
let title: String
let message: String
if error is LoginError {
title = "ϩάΠϯΤϥʔ"
message
= "ID·ͨ͸ύεϫʔυ͕ਖ਼͋͘͠Γ·ͤΜɻ"
} else ...

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loginButtonPressed
sender: UIButton) {
Task { ...
do { ... } catch { ...
let alertController: UIAlertController
= .init(title: title, message: message,
preferredStyle: .alert)
alertController
.addAction(.init(title: "ด͡Δ",
style: .default, handler: nil))
present(alertController, animated: true)
}

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ViewModel Λಋೖ

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UIKit Λར༻͢ΔίʔυͱͦΕҎ֎Λ෼཭

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LoginViewModel
import Combine
final class LoginViewModel {
@Published var id: String = ""
@Published var password: String = ""
@Published private(set) var isLoginButtonEnabled:
Bool = true
}

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LoginViewModel
import Combine
final class LoginViewModel: ObservableObject {
Bool = true
}

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LoginViewModel
import Combine
@MainActor
Bool = true
}

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!
ViewModel Λ MainActor Ͱอޢ͢Δ

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LoginViewModel
import Combine
@MainActor
...
func loginButtonPressed() async {
...
}
}

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LoginViewController.loginButtonPressed
// LoginViewController
Task {
do {
...
} catch {
...
}
}
}

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Task {
}
}

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Task {
await viewModel.loginButtonPressed()
}
}

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LoginViewModel.loginButtonPressed
// LoginViewModel
}

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// LoginViewModel
isLoginButtonEnabled = false
defer { isLoginButtonEnabled = true }
do {
...
} catch {
...
}
}

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!
Task.init Λ ViewModel Ͱ͸ͳ͘
View ଆʹॻ͘
※ ViewModel ͷςετ͕ॻ͖΍͘͢ͳΔ
※ ͨͩ͠ɺ ViewModel ͰΩϟϯηϧΛѻ͍ͮΒ͘ͳΔ

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WWDC2021 10019 h*ps:/
/developer.apple.com/videos/play/wwdc2021/10019/

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// LoginViewModel
...
}

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isLoginButtonEnabled ͷ View ΁ͷ൓ө
override func viewDidLoad() {
super.viewDidLoad()
...
viewModel.$isLoginButtonEnabled
.sink { [weak self] isEnabled in
guard let self else { return }
self.loginButton.isEnabled = isEnabled
}
.store(in: &cancellables)

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// LoginViewModel
...
}

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// LoginViewModel
do {
dismiss.send()
} catch {
...
}
}

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LoginViewModel.dismiss
@MainActor
...
let dismiss: PassthroughSubject = .init()
...
}

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dismiss ͷ View Ͱͷ࣮ߦ
override func viewDidLoad() {
super.viewDidLoad()
...
viewModel.dismiss
.sink { [weak self] _ in
self?.parent?.dismiss(animated: true)
}
.store(in: &cancellables)

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// LoginViewModel
...
do { ... } catch {
...
} else ...
}
}

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// LoginViewModel
...
do { ... } catch {
presentLoginErrorAlert.send(...)
} else ...
}
}

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// LoginViewModel
...
do { ... } catch {
loginErrorMessage = .login
} else ...
}
}

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LoginViewModel.loginErrorMessage
@MainActor
...
@Published var loginErrorMessage: LoginErrorMessage?
...
}

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LoginErrorMessage
enum LoginErrorMessage: Hashable {
case login
case network
case server
case system
}

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Swi$UI
struct LoginView: View {
@StateObject private var viewModel:
LoginViewModel = .init()
...
}

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Swi$UI
...
var body: some View {
VStack(alignment: .center) {
Spacer()
TextField("ID", text: $viewModel.id)
.textInputAutocapitalization(.never)
.textFieldStyle(.roundedBorder)
.frame(width: 200)
...

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Swi$UI
...
VStack(alignment: .center) {
...
Button("Log in") {
Task {
await viewModel
.loginButtonPressed()
}
}
...

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Swi$UI
...
VStack(alignment: .center) { ... }
.onReceive(viewModel.dismiss) { _ in
dismiss()
}
...
}
}

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Swi$UI
...
@Environment(\.dismiss) private var dismiss
VStack(alignment: .center) { ... }
.onReceive(viewModel.dismiss) { _ in
dismiss()
}
...
}
}

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DI ͱςετ

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LoginViewModel ͷςετ͕ॻ͖ͮΒ͍
do {
// αʔόʔʹΞΫηεɺϑΝΠϧ I/O
dismiss.send()
} catch {
...
}
}

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ςετ͔Βαʔόʔ΍ϑΝΠϧʹΞΫηεͨ͘͠ͳ͍
• ωοτϫʔΫ΍αʔόʔͷঢ়ଶͰ݁Ռ͕ෆఆ
• ੒ޭɾࣦഊέʔεͳͲΛ੍ޚͰ͖ͳ͍
• ςετͷ౓ʹσʔλΛॻ͖ࠐΈͨ͘ͳ͍

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ಠཱͨ͠ίΞϨΠϠʔύλʔϯ
Core Layer Pa*ern h*ps:/
/blog.shin1x1.com/entry/independent-core-layer-pa*ern

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AuthServiceProtocol
protocol AuthServiceProtocol {
static var shared: Self { get }
func logIn(
for id: User.ID,
) async throws
...
}

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AuthService
actor AuthService: AuthServiceProtocol {
...
}

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LoginViewModel
@MainActor
final class LoginViewModel:
ObservableObject {
...
}

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LoginViewModel
@MainActor
final class LoginViewModel:
ObservableObject
where AuthService: AuthServiceProtocol {
...
}

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ܕύϥϝʔλΠϯδΣΫγϣϯ

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AuthService ͷར༻Օॴͷίʔυ͸มΘΒͳ͍
do {
dismiss.send()
} catch {
...
}
}

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!
DI Λ׆༻ͯ͠ ViewModel Λ
UI ΍ωοτϫʔΫ౳͔Β
ಠཱͤ͞Δ

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LoginViewModelTests
@MainActor
final class LoginViewModelTests: XCTestCase {
...
}

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loginErrorMessage ͷςετ
func testLoginErrorMessageByLoginError() async {
let viewModel: LoginViewModel = .init()
...
}

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await viewModel.loginButtonPressed() // LoginError
...
}

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XCTAssertEqual(viewModel.loginErrorMessage, .login)
}

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!
async/await Λ࢖͑͹
ඇಉظϝιουͷςετΛ
γϯϓϧʹॻ͚Δ
※ Task.init Λ ViewModel ଆʹॻ͔ͳ͔͔ͬͨΒͦ͜

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}

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ςετ༻ͷ AuthService
private final class AuthService: AuthServiceProtocol {
static var shared: AuthService = .init()
private init() {}
...
}

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...
func logIn(for id: User.ID, with password: String)
async throws {
throw LoginError()
}
}

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...
var logInResult: Result?
async throws {
try logInResult!.get()
}
}

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}

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AuthService.shared.logInResult
= .failure(LoginError())
}

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func testLoginErrorMessageByServerError() async {
AuthService.shared.logInResult
= .failure(ServerError.response(...))
XCTAssertEqual(viewModel.loginErrorMessage, .server)
}

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isLoginButtonEnabled ͷςετ
func testLoginButtonEnabled() async {
...
}

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XCTAssertTrue(viewModel.isLoginButtonEnabled)
...
}

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viewModel.loginButtonPressed()
...
}

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XCTAssertFalse(viewModel.isLoginButtonEnabled)
...
}

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...
}

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async let logIn: Void
= viewModel.loginButtonPressed()
await logIn
}

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AuthService.shared.???
await logIn

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...
var logInResult: Result?
async throws {
try logInResult!.get()
}
}

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...
var logInContinuation: CheckedContinuationError>?
async throws {
try await withCheckedThrowingContinuation
{ continuation in
logInContinuation = continuation
}
}
}

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...
AuthService.shared.???
await logIn

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...
AuthService.shared.logInContinuation?
.resume(returning: ())
await logIn

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...
await Task.yield()
await logIn

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...
while AuthService.shared.logInContinuation == nil {
await Task.yield()
}
await logIn

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...
while AuthService.shared.logInContinuation == nil {
await Task.yield()
}
AuthService.shared.logInContinuation = nil
await logIn

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...
await logIn
}

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·ͱΊ
• async/await, Sendable, Con'nua'on, Task, actor,
MainActor
• ViewModel ͷಋೖͱඇಉظॲཧͷςετ

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͝ਗ਼ௌ͋Γ͕ͱ͏͍͟͝·ͨ͠ʂ

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Swift Concurrency時代のiOSアプリの作り方

Swift Concurrency時代のiOSアプリの作り方

Yuta Koshizawa

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