【Xcode 15】將我們綁在一起吧，伊莎貝爾 - Combine

// MARK: - 小工具
private extension ViewController {

    /// [初始化設定輸入框有輸入時的動作](https://blog.csdn.net/u013538542/article/details/134426757)
    func editingChangedSetting() {
        
        keyboardHeightConstraint.constant = 0
        
        let textFields: [UserTextFieldType: UITextField] = [
            .username: usernameTextField,
            .eMail: eMailTextField,
            .password: passwordTextField,
        ]
        
        UserTextFieldType.allCases.forEach { type in
            
            guard let textField = textFields[type] else { return }
            
            textField.delegate = self
            textField.tag = type.rawValue
            textField._editingChanged { self.storeInputText(with: $0) }
        }
    }
    
    /// [把輸入的值存起來 (單向：輸入框輸入文字 -> 存變數 / 正在輸入的注音不算)](https://www.swiftbysundell.com/articles/combine-self-cancellable-memory-management/)
    /// - Parameter textField: UITextField
    func storeInputText(with textField: UITextField) {
        
        guard textField.markedTextRange == nil,
              let type = UserTextFieldType(rawValue: textField.tag)
        else {
            return
        }
        
        switch type {
        case .username: viewModel.username = textField.text ?? ""
        case .eMail: viewModel.eMail = textField.text ?? ""
        case .password: viewModel.password = textField.text ?? ""
        }
    }
}

final class ViewController: UIViewController {
    
    private var viewModel = RegistrationViewModel()
}

final class RegistrationViewModel: ObservableObject {
    
    @Published var username: String = ""                                        // 帳號
    @Published var eMail: String = ""                                           // 電子郵件
    @Published var password: String = ""                                        // 密碼

    var canRegister: AnyPublisher<Bool, Never> { return canRegisterRule() }     // 可不可以註冊
}

extension RegistrationViewModel {
    
    /// [清除](https://medium.com/彼得潘的-swift-ios-app-開發問題解答集/使用-preview-macro-定義預覽畫面-ios-17-新功能-bc850b2c11fc)
    func clean() {
        username = ""; eMail = ""; password = ""
    }
}

private extension RegistrationViewModel {
    
    /// [可以註冊的規則 (通通要有值)](https://zhuanlan.zhihu.com/p/150958669)
    /// - Returns: [AnyPublisher<Bool, Never>](https://developer.apple.com/videos/play/wwdc2021/10022/)
    func canRegisterRule() -> AnyPublisher<Bool, Never> {
        
        let rule = Publishers.CombineLatest3($username, $eMail, $password)
            .map { username, email, password in return !username.isEmpty && !email.isEmpty && !password.isEmpty }
            .eraseToAnyPublisher()

        return rule
    }
}

// MARK: - Combine
private extension ViewController {
    
    /// [清除輸入值 => 同時也會清除輸入框](https://onevcat.com/2020/06/stateobject/)
    func clearInputValuesAction() {
        viewModel.clean()
        view.endEditing(true)
    }
    
    /// [綁定ViewModel (單向：變數內容改變 -> 輸入框文字改變)](https://medium.com/jeremy-xue-s-blog/swift-使用-combine-處理-url-任務-8a48d0dc3b1b)
    func viewModelSetting() {
        
        viewModel.$username
            .sink { [weak self] newText in self?.usernameTextField.text = "\(newText)" }
            .onCancel { wwPrint("[onCancel] viewModel.$username") }
            .store(in: &cancellables)
        
        viewModel.$eMail
            .sink { [weak self] newText in self?.eMailTextField.text = "\(newText)" }
            .onCancel { wwPrint("[onCancel] viewModel.$eMail") }
            .store(in: &cancellables)
        
        viewModel.$password
            .sink { [weak self] newText in self?.passwordTextField.text = "\(newText)" }
            .onCancel { wwPrint("[onCancel] viewModel.$password") }
            .store(in: &cancellables)
    }
    
    /// [針對ViewModel數值改變時的處理 (註冊按鈕的顏色變化)](https://zhuanlan.zhihu.com/p/343631974)
    func viewModelActionSetting() {
        
        viewModel.canRegister.sink { canRegister in
            self.registerButton.isEnabled = canRegister
            self.registerButton.backgroundColor = !canRegister ? .darkGray : .systemRed
        }.onCancel { wwPrint("[onCancel] viewModel.canRegister") }
        .store(in: &cancellables)
    }
}

private extension ViewController {

    /// [取得鍵盤相關資訊後的相關處理](https://medium.com/彼得潘的-swift-ios-app-開發問題解答集/swiftui-view-的生命週期影響-stateobject-state-儲存的資料-ffd4982fcece)
    /// - Parameter info: [Constant.KeyboardInformation](https://waynestalk.com/swift-combine/)
    func keyboardAction(with info: Constant.KeyboardInformation) {
        
        let isHidden = info.beginFrame.origin.y < info.endFrame.origin.y
        let curve = UIView.AnimationCurve(rawValue: Int(info.curve)) ?? .linear
        keyboardHeightConstraint.constant = isHidden ? 0 : info.endFrame.height
        
        UIViewPropertyAnimator(duration: info.duration, curve: curve) {
            self.view.layoutIfNeeded()
        }.startAnimation()
    }
    
    /// [鍵盤出現與否的設定功能 (有點像事件通知)](https://fatbobman.com/zh/posts/exploring-key-property-wrappers-in-swiftui/)
    func keyboardActionSetting() {
        
        NotificationCenter.default.publisher(for: UIResponder.keyboardWillShowNotification)
            .compactMap { notification in return UIDevice._keyboardInformation(notification: notification) }
            .sink { info in self.keyboardAction(with: info) }
            .onCancel { wwPrint("[onCancel] UIResponder.keyboardWillShowNotification") }
            .store(in: &cancellables)
        
        NotificationCenter.default.publisher(for: UIResponder.keyboardWillHideNotification)
            .compactMap { notification in return UIDevice._keyboardInformation(notification: notification) }
            .sink { info in self.keyboardAction(with: info) }
            .onCancel { wwPrint("[onCancel] UIResponder.keyboardWillHideNotification") }
            .store(in: &cancellables)
    }
}

// MARK: - 使用者註冊頁
final class ViewController: UIViewController {

    private var viewModel = RegistrationViewModel()
    private var cancellables: Set<AnyCancellable> = []
    
    override func viewDidLoad() {
        super.viewDidLoad()
        initSetting()
    }
    
    override func viewWillAppear(_ animated: Bool) {
        super.viewWillAppear(animated)
        combineSetting()
    }
    
    override func viewWillDisappear(_ animated: Bool) {
        super.viewWillDisappear(animated)
        cancellables = []
    }
    
    override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
        prepareSegueAction(segue, sender: sender)
    }
}

import UIKit
import Combine
import WWPrint

// MARK: - 測試頁
final class NextViewController: UIViewController {

    typealias HttpOutput = Result<Data?, HttpError>

    enum HttpError: Error {
        case response
        case code(_ code: Int)
    }
    
    @IBOutlet weak var myImageView: UIImageView!
    
    var viewModel: RegistrationViewModel!
    
    private let imageUrl = (
        original: "https://i.ytimg.com/vi/TX9qSaGXFyg/maxresdefault.jpg",
        backup: "https://www.digitaltrends.com/wp-content/uploads/2023/06/WWDC-2023-Apple-Vision-Pro-1.jpg"
    )
    
    private var cancellables: Set<AnyCancellable> = []
    
    override func viewDidLoad() {
        super.viewDidLoad()
        initSetting()
    }
}

// MARK: - 小工具
private extension NextViewController {
    
    /// [初始化設定](https://medium.com/彼得潘的-swift-ios-app-開發問題解答集/ios-combine-學習參考資源-a0ac24f348d4)
    func initSetting() {
        title = viewModel.username
        viewModel.clean()
        downloadImageWithURL(original: imageUrl.original, backup: imageUrl.backup)
    }
    
    /// [下載網路圖片](https://lochiwei.gitbook.io/ios/frameworks/combine/publishers/urlsession.datataskpublisher)
    /// - Parameters:
    ///   - originalUrlString: [原始圖片URL](https://www.jianshu.com/p/157978e2f283)
    ///   - backupUrlString: [備用圖片URL](https://zhuanlan.zhihu.com/p/343631974)
    func downloadImageWithURL(original originalUrlString: String, backup backupUrlString: String) {
        
        guard let originalUrl = URL(string: originalUrlString),
              let backupUrl = URL(string: backupUrlString)
        else {
            return
        }
                        
        URLSession.shared
            .dataTaskPublisher(for: originalUrl)                                                    // 將這個URL給dataTaskPublisher處理
            .receive(on: DispatchQueue.global())                                                    // 在global序執行
            .retry(3)                                                                               // 可以重試3次
            .print("[Download]")                                                                    // 顯示處理的訊息
            .catch({ error in return self.retryErrorAction(error: error, backupUrl: backupUrl) })   // 如果有錯誤的話，轉成新的dataTaskPublisher處理
            .tryMap { output -> HttpOutput in return try self.responseAction(output: output) }
            .sink { error in wwPrint(error) } receiveValue: { result in self.receiveResultAction(result: result) }
            .store(in: &cancellables)
    }
}

// MARK: - 小工具
private extension NextViewController {
    
    /// retry失敗後的處理 (下載另一張新的圖)
    /// - Parameters:
    ///   - error: URLSession.DataTaskPublisher.Failure
    ///   - backupUrl: URL
    /// - Returns: URLSession.DataTaskPublisher
    func retryErrorAction(error: URLSession.DataTaskPublisher.Failure, backupUrl: URL) -> URLSession.DataTaskPublisher {
        
        let session = URLSession(configuration: .default, delegate: nil, delegateQueue: .main)
        let publisher = session.dataTaskPublisher(for: backupUrl)
         
        return publisher
    }
    
    /// 處理取到Output而後的處理 (HTTPURLResponse)
    /// - Parameter output: URLSession.DataTaskPublisher.Output
    /// - Returns: HttpOutput
    func responseAction(output: URLSession.DataTaskPublisher.Output) throws -> HttpOutput {
        
        guard let httpResponse = output.response as? HTTPURLResponse,
              let statusCode = Optional.some(httpResponse.statusCode)
        else {
            throw HttpError.response
        }

        if (statusCode != 200) { throw HttpError.code(statusCode) }
        return HttpOutput.success(output.data)
    }
    
    /// 最後的結果處理 (網路連線正常，也有取得回應)
    /// - Parameter result: HttpOutput
    func receiveResultAction(result: HttpOutput) {
        
        switch result {
        case .failure(let error):

            switch error {
            case .code(let code): wwPrint(code)
            case .response: wwPrint("response error")
            }

        case .success(let data):
            
            guard let data = data else { return }
            
            DispatchQueue.main.async {
                wwPrint(Thread.current)
                self.myImageView.image = UIImage(data: data)
            }
            
            wwPrint(Thread.current)
        }
    }
}