13, 14

• 13: Publisher, CloudKit, CoreData
• 14: App Architecture, Document Architecture, Undo

Publisher

// fetch the url
backgroundImageFetchStatus = .fetching

DispatchQueue.global(qos: .userInitiated).async {
    let imageData = try? Data(contentsOf: url)
    DispatchQueue.main.async { [weak self] in
        if self?.emojiArt.background == EmojiArtModel.Background.url(url) {
            self?.backgroundImageFetchStatus = .idle
            if imageData != nil {
                self?.backgroundImage = UIImage(data: imageData!)
            }
        }
    }
}

// fetch the url
backgroundImageFetchStatus = .fetching

let session = URLSession.shared
let publisher = session.dataTaskPublisher(for: url)
    .map { (data, urlResponse) in UIImage(data: data) }
    .replaceError(with: nil)
    .receive(on: DispatchQueue.main)

backgroundImageFetchCancellable = publisher
    .sink { [weak self] image in
        self?.backgroundImage = image
        self?.backgroundImageFetchStatus = image != nil ? .idle : .failed(url)
    }

1. 取得 Publisher (subscription)
2. Publisher 設定
   • .map(_:) 改變產物
   • .receive(on: DispatchQueue.main)
3. Publisher 資料接收
   • .sink(receiveValue:) 處理產出的資料
4. Cancellable 保存與使用

Publisher 有很多 method 很像 array 的 method，.map(_:)

• URLSession
• Timer
• NotificationCenter

CoreData

• @ObservedObject
• @FetchRequest

App Architecture

• App protocol
• Scene protocol
  • WindowGroup { }
  • DocumentGroup(newDocument:) { }
  • DocumentGroup(viewing:) { }
• @SenceStorage
• @AppStorage
• @ScaledMetric

@SceneStorage("EmojiArtDocument.steadyStatePanOffset")
var steadyStatePanOffset: CGSize = .zero

@SceneStorage("EmojiArtDocumentView.steadyStateZoomScale")
var steadyStateZoomScale: CGFloat = 1

@AppStorage("username") 
var username: String = "Anonymous"

• 被存在 UserDefaults.standard
  • 所以不推薦存大量資料
  • 所以不要存機敏性資料

7:48 Code

app icon -> Asset.xcassets

19:56 RawRepresentable

每次開啟 app 後 load backgroundImage 完成又去 zoomToFit

28:02 Document Architecture

• FileDocument
• ReferenceFileDocument
• UTType
• Document Types
• 39:05 Undo

func undoablyPerform(operation: String, with undoManager: UndoManager?) {
    let oldModel = model
    doIt()
    undoManager?.registerUndo(withTarget: self) { mySelf in
        mySelf.model = oldModel
    }
    undoManager?.setActionName(operation)
}

43:14 Back To Code

• 49:50 讓 ViewModel conform to ReferenceFileDocument
• 1:02:16 undo imple
• 1:12:01 support document

https://github.com/skkimeo/CS193p-Spring-2021