ios - 如何将 ObservableObject 与 UIViewRepresentable 一起使用

Question

我正在使用 MVVM 构建一个 SwiftUI 应用。

我需要一些额外的文本字段行为，所以我将 UITextField 包装在 UIViewRepresentable View 中。

如果我在包含我的文本字段的 View 中使用简单的 @State 来绑定(bind)文本，自定义文本字段将按预期运行；但是因为我想在 View 模型中存储我的文本字段的所有文本，所以我使用了 @ObservedObject;使用它时，文本字段绑定(bind)不起作用:它看起来总是重置为初始状态(空文本)并且它不发布任何值(并且 View 不刷新)。这种奇怪的行为只发生在 UIViewRepresentable View 中。

我的主视图包含一个表单，它看起来像这样:

struct LoginSceneView: View {

    @ObservedObject private var viewModel: LoginViewModel = LoginViewModel()

    var body: some View {
        ScrollView(showsIndicators: false) {
            VStack(spacing: 22) {
                UIKitTextField(text: $viewModel.email, isFirstResponder: $viewModel.isFirstResponder)
                SecureField("Password", text: $viewModel.password)
                Button(action: {}) {
                    Text("LOGIN")
                }
                .disabled(!viewModel.isButtonEnabled)       
            }
            .padding(.vertical, 40)
        }
    }

}

View 模型是这样的:

class LoginViewModel: ObservableObject {

    @Published var email = ""
    @Published var password = ""
    @Published var isFirstResponder = false

    var isButtonEnabled: Bool { !email.isEmpty && !password.isEmpty }

}

最后，这是我的自定义文本字段:

struct UIKitTextField: UIViewRepresentable {

    // MARK: - Coordinator

    class Coordinator: NSObject, UITextFieldDelegate {

        private let textField: UIKitTextField

        fileprivate init(_ textField: UIKitTextField) {
            self.textField = textField

            super.init()
        }

        @objc fileprivate func editingChanged(_ sender: UITextField) {
            let text = sender.text ?? ""
            textField.text = text
            textField.onEditingChanged(text)
        }

        func textFieldDidBeginEditing(_ textField: UITextField) {
            self.textField.onEditingBegin()
        }

        func textFieldDidEndEditing(_ textField: UITextField) {
            self.textField.onEditingEnd()
        }

        func textFieldShouldReturn(_ textField: UITextField) -> Bool {
            self.textField.onReturnKeyPressed()
        }

    }

    // MARK: - Properties

    @Binding private var text: String
    private let onEditingChanged: (String) -> Void
    private let onEditingBegin: () -> Void
    private let onEditingEnd: () -> Void
    private let onReturnKeyPressed: () -> Bool

    // MARK: - Initializers

    init(text: Binding<String>,
         onEditingChanged: @escaping (String) -> Void = { _ in },
         onEditingBegin: @escaping  () -> Void = {},
         onEditingEnd: @escaping  () -> Void = {},
         onReturnKeyPressed: @escaping  () -> Bool = { true }) {
        _text = text
        self.onEditingChanged = onEditingChanged
        self.onEditingBegin = onEditingBegin
        self.onEditingEnd = onEditingEnd
        self.onReturnKeyPressed = onReturnKeyPressed
    }

    // MARK: - UIViewRepresentable methods

    func makeCoordinator() -> Coordinator { Coordinator(self) }

    func makeUIView(context: Context) -> UITextField {
        let textField = UITextField()
        textField.delegate = context.coordinator
        textField.setContentHuggingPriority(.defaultHigh, for: .vertical)
        textField.addTarget(context.coordinator, action: #selector(Coordinator.editingChanged(_:)), for: .editingChanged)
        return textField
    }

    func updateUIView(_ uiView: UITextField, context: Context) {
        uiView.text = text
    }

}

Answer 1

您的问题可能是每次更改某些绑定(bind)变量时都会创建 UIViewRepresentable。放入调试代码进行检查。

struct UIKitTextField: UIViewRepresentable {
    init() {
         print("UIViewRepresentable init()")
    }
    ...
}