Boundaries In Practice // 実践的 “Boundaries”

Talk given 3 Mar 2016 at try! Swift Tokyo

// Boundaries In Practice
One of the talks that I’ve enjoyed watching is Boundaries by Gary Bernhardt (https://www.destroyallsoftware.com/talks/boundaries). If you’ve seen a talk about functional programming in Swift, you’ve probably heard it being referenced. When I first watched the talk a few years ago, I understood the theory but wasn’t sure where exactly to apply the concepts. As I’ve been writing more and more Swift, I started to see that the concept of “Functional Core, Imperative Shell” applies not just to functional programming, but also to good engineering in general. In this talk, we’ll go over a couple of specific examples how these “boundaries” can help us write better, safer, and more future-proof Swift code. You don’t need to watch the Boundaries talk to understand this talk, but if you have time, definitely watch it because it’s a great talk.

// 実践的 “Boundaries”
Gary BernhardtさんのBoundariesの講演 (https://www.destroyallsoftware.com/talks/boundaries) 、ご存知ですか。ファンクショナルプログラミングの講演で良く参照される講演です。私は数年前に初めてこの講演を観た時、「Functional Core, Imperative Shell」の理論は理解できたのですが、実際どの様にこのコンセプトを実用化できるのか良く分かりませんでした。しかし、毎日少しずつSwiftを書いているうちに、このコンセプトはファンクショナルプログラミングだけではなく、良いエンジニアリングに一般的に適用できるのが明らかになってきました。今回はどの様に「Boundaries」を利用して、もっと良い、もっと安全なそして将来性のあるSwiftを書くことが出来るのかを幾つかの事例を紹介しながらお話しさせて頂きます。「Boundaries」をご覧になった事がなくても私の話をご理解頂けると思いますが、もしお時間があれば是非一度ご覧下さい。素晴らしい話です。

Transcript

1. ࣮ફత
   BOUNDARIES
   IN PRACTICE
   TRY! SWIFT 2016
   

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2. HI, I’M AYAKA.
   A.K.A. ࠼Ֆ
   @AYANONAGON
   

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3. View Slide

4. FUNCTIONAL CORE
   IMPERATIVE SHELL
   

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5. FUNCTIONAL CORE
   

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6. APP = MANY FUNCTIONAL CORES
   

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7. WITH IMPERATIVE SHELLS
   

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8. “ALL YOU REALLY KNOW MAYBE IS THAT
   YOUR TASTE IS IMPROVING A LOT
   FASTER THAN YOUR ABILITY.”
   ANDY MATUSCHAK, ADVANCED IOS APPLICATION ARCHITECTURE AND PATTERNS (WWDC 2014)
   

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9. ࣮ફత
   BOUNDARIES
   IN PRACTICE
   TRY! SWIFT 2016
   

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10. ୈҰ
    IMMUTABLE CORE
    NETWORK-Y SHELL
    ෆมͳਊɺωοτϫʔΫͬΆ͍ද໘
    

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11. View Slide

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13. struct Story {
    let ID: String
    let title: String
    let message: String
    let sender: User
    let recipient: User
    let date: NSDate
    // ...
    }
    

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14. class StoriesViewController: UIViewController {
    let stories: [Story]
    // ...
    }
    

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15. class StoryDetailViewController: UIViewController {
    init(story: Story)
    }
    

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16. class StoryDetailViewController: UIViewController {
    private let titleView: StoryTitleView
    private let senderView: AvatarView
    private let recipientView: AvatarView
    private let dateLabel: DateLabel
    init(story: Story) {
    titleView = StoryTitleView(story: story)
    senderView = AvatarView(user: story.sender)
    recipientView = AvatarView(user: story.recipient)
    dateLabel = DateLabel(date: story.date)
    }
    // ...
    }
    

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17. url_scheme://stories/12345
    

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18. class StoryDetailViewController: UIViewController {
    init(story: Story)
    }
    

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19. class StoryDetailViewController: UIViewController {
    init(story: Story)
    init(storyID: String)
    }
    

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20. class StoryDetailViewController: UIViewController {
    private let titleView: StoryTitleView
    private let senderView: AvatarView
    private let recipientView: AvatarView
    private let dateLabel: DateLabel
    init(story: Story) { /* Same as before લͱಉ͡ */ }
    init(storyID: String) {
    // Hmmmmmmm.ɹ͜ΕԿͩΖ͏ʁ
    }
    }
    

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21. class StoryDetailViewController: UIViewController {
    let storyID: String
    private var titleView: StoryTitleView?
    private var senderView: AvatarView?
    private var recipientView: AvatarView?
    private var dateLabel: DateLabel?
    init(story: Story) { /* Same as before લͱಉ͡ */ }
    init(storyID: String) {
    self.storyID = storyID
    titleView = nil
    senderView = nil
    recipientView = nil
    dataLabel = nil
    }
    // Load everything from API in viewDidLoad?
    // viewDidLoadͰAPI͔Βϩʔυʁ!ɹ
    }
    

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22. class StoryContainerViewController: UIViewController {
    let storyID: String
    init(storyID: String) {
    self.storyID = storyID
    }
    override func viewDidLoad() {
    client.showStory(ID: storyID) { result in
    switch result {
    case .Success(let story):
    let viewController = StoryDetailViewController(story: story)
    self.addChildViewController(viewController)
    self.view.addSubview(viewController.view)
    viewController.view.frame = view.bounds
    viewController.didMoveToParentViewController(self)
    case .Error(let error): // Show errorɹΤϥʔදࣔ
    }
    }
    }
    }
    

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23. url_scheme://stories/12345
    StoryContainerViewController(storyID: "12345")
    

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24. url_scheme://stories/12345
    

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25. url_scheme://stories/12345
    url_scheme://users/007
    

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26. url_scheme://stories/12345
    url_scheme://users/007
    url_scheme://messages/9876
    

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27. protocol RemoteContentProviding {
    typealias Content
    func fetchContent(completion: Result -> Void)
    func viewControllerForContent(content: Result) -> UIViewController
    }
    

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28. class RemoteContentContainerViewController: UIViewController {
    let provider: T
    init(provider: T) {
    self.remoteContentProvider = remoteContentProvider
    super.init(nibName: nil, bundle: nil)
    }
    override func viewDidLoad() {
    super.viewDidLoad()
    provider.fetchContent { content in
    let viewController = self.provider.viewControllerForContent(content)
    self.addChildViewController(viewController)
    self.view.addSubview(viewController.view)
    viewController.view.frame = view.bounds
    viewController.didMoveToParentViewController(self)
    }
    }
    }
    

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29. struct StoryProvider: RemoteContentProviding {
    let ID: String
    func fetchContent(completion: Result -> Void) {
    client.showStory(ID: ID, completion: completion)
    }
    func viewControllerForContent(content: Result) -> UIViewController {
    switch content {
    case .Success(let story): return StoryDetailViewController(story: story)
    case .Error(_): return ErrorViewController(title: "Could not find story.")
    }
    }
    }
    

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30. url_scheme://stories/12345
    let provider = StoryProvider(ID: "12345")
    RemoteContentContainerViewController(provider: provider)
    

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31. url_scheme://users/007
    let provider = UserProvider(ID: "007")
    RemoteContentContainerViewController(provider: provider)
    

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32. url_scheme://messages/9876
    let provider = MessageProvider(ID: "9876")
    RemoteContentContainerViewController(provider: provider)
    

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33. class StoryDetailViewController: UIViewController {
    let storyID: String
    private var titleView: StoryTitleView?
    private var senderView: AvatarView?
    private var recipientView: AvatarView?
    private var dateLabel: DateLabel?
    init(story: Story) { /* Same as before */ }
    init(storyID: String) {
    self.storyID = storyID
    titleView = nil
    senderView = nil
    recipientView = nil
    dataLabel = nil
    }
    // Load everything from API in viewDidLoad?
    // viewDidLoadͰAPI͔Βϩʔυʁ!
    }
    

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34. View Slide

35. class StoryDetailViewController: UIViewController {
    private let titleView: StoryTitleView
    private let senderView: AvatarView
    private let recipientView: AvatarView
    private let dateLabel: DateLabel
    init(story: Story) {
    titleView = StoryTitleView(story: story)
    senderView = AvatarView(user: story.sender)
    recipientView = AvatarView(user: story.recipient)
    dateLabel = DateLabel(date: story.date)
    }
    // ...
    }
    

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37. ୈೋ
    INDEPENDENT CORES
    CONNECTIVE SHELL
    ಠཱͨ͠ਊͱܨ͛Δද໘
    

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39. COORDINATORS
    SOROUSH KHANLOU @ NSSPAIN
    

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40. VIEW CONTROLLERS DON’T KNOW
    ABOUT OTHER VIEW CONTROLLERS
    

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41. @UIApplicationMain
    class AppDelegate: UIResponder, UIApplicationDelegate {
    var window: UIWindow?
    private lazy var applicationCoordinator: ApplicationCoordinator = {
    return ApplicationCoordinator(window: self.window!)
    }()
    func application(application: UIApplication, didFinishLaunchingWithOptions
    launchOptions: [NSObject: AnyObject]?) -> Bool {
    window = UIWindow(frame: UIScreen.mainScreen().bounds)
    applicationCoordinator.start()
    return true
    }
    }
    

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42. protocol Coordinator {
    func start()
    }
    

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43. class ApplicationCoordinator: Coordinator {
    let window: UIWindow
    let rootViewController = UITabBarController()
    let wordsNavigationController = UINavigationController()
    let phrasesNavigationController = UINavigationController()
    let wordsCoordinator: WordsCoordinator
    let phrasesCoordinator: PhrasesCoordinator
    init(window: UIWindow) {
    self.window = window
    let viewControllers = [wordsNavigationController, phrasesNavigationController]
    self.rootViewController.setViewControllers(viewControllers, animated: false)
    self.wordsCoordinator = WordsCoordinator(presenter: wordsNavigationController)
    self.phrasesCoordinator = PhrasesCoordinator(presenter: phrasesNavigationController)
    }
    func start() {
    window.rootViewController = rootViewController
    wordsCoordinator.start()
    phrasesCoordinator.start()
    window.makeKeyAndVisible()
    }
    }
    

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44. class WordsCoordinator: Coordinator {
    let presenter: UINavigationController
    private let listViewController: ListViewController
    private let dataSource: WordsDataSource
    init(presenter: UINavigationController) {
    self.presenter = presenter
    self.dataSource = WordsDataSource()
    self.listViewController = ListViewController()
    self.listViewController.title = "Words"
    self.listViewController.items = dataSource.words
    self.listViewController.configureCell = { cell, item in
    cell.item = item
    }
    self.listViewController.didSelectItem = { item in
    presenter.pushViewController(WordViewController(word: item), animated: true)
    }
    }
    func start() {
    presenter.pushViewController(listViewController, animated: false)
    }
    }
    

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45. class PhrasesCoordinator: Coordinator {
    let presenter: UINavigationController
    private let listViewController: ListViewController
    private let dataSource: PhrasesDataSource
    init(presenter: UINavigationController) {
    self.presenter = presenter
    self.dataSource = PhrasesDataSource()
    self.listViewController = ListViewController()
    self.listViewController.title = "Phrases"
    self.listViewController.items = dataSource.phrases
    self.listViewController.configureCell = { cell, item in
    cell.item = item
    }
    self.listViewController.didSelectItem = { item in
    presenter.pushViewController(PhraseViewController(phrase: item), animated: true)
    }
    }
    func start() {
    presenter.pushViewController(listViewController, animated: false)
    }
    }
    

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46. ApplicationCoordinator
    / \
    WordsCoordinator PhrasesCoordinator
    

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47. ApplicationCoordinator
    / \
    WordsCoordinator PhrasesCoordinator
    /
    SearchCoordinator
    

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48. ApplicationCoordinator
    / \
    DictionaryCoordinator LoginCoordinator
    / \
    WordsCoordinator PhrasesCoordinator
    /
    SearchCoordinator
    

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49. ApplicationCoordinator
    / \ \
    DictionaryCoordinator LoginCoordinator SignUpCoordinator
    / \
    WordsCoordinator PhrasesCoordinator
    /
    SearchCoordinator
    

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52. ந৅Խ
    ABSTRACTION
    

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53. ݎ࣮
    SOLID
    

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54. ྲྀಈత
    FLUID
    

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55. ྲྀಈత 㲗 ݎ࣮
    FLUID 㲗 SOLID
    

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56. কདྷੑ
    FUTURE PROOF
    

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57. THANK YOU
    ͋Γ͕ͱ͏ʂ
    

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