Question

我正在学习MVVM + RxSwift。我想保存一个值以在下一个流程中重用它。但是我遇到了上面的错误。

我假设我初始化了一个名为“ translatedText”的值，但错误仍然出现。

我尝试了一些使用声明进行初始化的方法，等等...


import UIKit
import RxSwift

final class ViewModel {


    private let api: apiProtocol
    let validationText: Observable<String>
    let getObservable: Observable<String>
    var translatedText: String
    // var translatedText: String = "" //this case also dosn't work

    init(inputObservable: Observable<String?>, changeButtonClicked: Observable<Void>, model: ModelProtocol, api: apiProtocol = APICntl()) {

        self.api = api
        self.translatedText = "" //I guess I initialised this here

        let event = inputObservable
            .flatMap { input -> Observable<Event<Void>> in
                if let text = input {
                    self.translatedText = text // error. i want to save "input" to use at "let tapEvent"
                }
                return model
                    .validate(text: input)
                    .materialize()
            }
            .share()

        self.validationText = event
            .flatMap { event -> Observable<String> in
                switch event {
                case .next:
                    return .just("")
                case let .error(error as ModelError):
                    return .just(error.errorLabel)
                case .error, .completed:
                    return .empty()
                }
            }
            .startWith(ModelError.invalidBlank.errorLabel)

        let tapEvent = changeButtonClicked
            .flatMap { (result) -> Observable<Event<String>> in
                return api
                    .fetch(text: self.translatedText) // I want use it here
                    .materialize()
        }
        .share()

        self.getObservable = tapEvent
            .flatMap { event -> Observable<String> in
                switch event {
                case .next:
                    return .just(event.element!)
                case let .error(error as ModelError):
                    return .just(error.errorLabel)
                case .error, .completed:
                    return .empty()
                }
            }
    }

}

你们有更好的解决方案吗？

-----自我解决方案-----

我只是简单地在let事件之前创建了一个临时变量，它可以按我的意愿工作。

final class ViewModel {


    private let api: apiProtocol
    let validationText: Observable<String>
    let getObservable: Observable<String>

    init(inputObservable: Observable<String?>, changeButtonClicked: Observable<Void>, model: ModelProtocol, api: apiProtocol = APICntl()) {

        self.api = api
        var temp = ""

        let event = inputObservable
            .flatMap { input -> Observable<Event<Void>> in
                if let text = input {
                    temp = text
                }
                return model
                    .validate(text: input)
                    .materialize()
            }
            .share()

Answer 1

您的问题是，调用self时flatMap尚未完全初始化。就您而言，validationText和getObservable处于未定义状态。

最快的方法是使它们隐式地展开为可选，但是您实际上必须保证在初始化之前不会访问它们：

final class ViewModel {


    private let api: apiProtocol
    let validationText: Observable<String>!
    let getObservable: Observable<String>!
    var translatedText: String!

    // ...
}

Answer 2

----自我解决方案-----

我只是简单地在let事件之前创建了一个临时变量，它可以按我的意愿工作。

final class ViewModel {


    private let api: apiProtocol
    let validationText: Observable<String>
    let getObservable: Observable<String>

    init(inputObservable: Observable<String?>, changeButtonClicked: Observable<Void>, model: ModelProtocol, api: apiProtocol = APICntl()) {

        self.api = api
        var temp = ""

        let event = inputObservable
            .flatMap { input -> Observable<Event<Void>> in
                if let text = input {
                    temp = text
                }
                return model
                    .validate(text: input)
                    .materialize()
            }
            .share()

Answer 3

您不应将两个独立的可观察流与带有“ temp”内存的随机块相互绑定。这两个流取决于inputObservable，应该明确说明。而且，您的视图模型可以大大简化...

final class ViewModel {
    let validationText: Observable<String>
    let getObservable: Observable<String>

    init(inputObservable: Observable<String?>, changeButtonClicked: Observable<Void>, model: ModelProtocol, api: apiProtocol = APICntl()) {

        let translatedText = inputObservable.share() // this line is unnecessary if `inputObservable` is already hot.

        self.validationText = translatedText
            .flatMap { input in
                return model
                    .validate(text: input)
                    .map { "" }
                    .catchError { error in .just((error as? ModelError)?.errorLabel ?? error.localizedDescription) }
            }
            .startWith(ModelError.invalidBlank.errorLabel)

        self.getObservable = changeButtonClicked
            .withLatestFrom(translatedText)
            .compactMap { $0 }
            .flatMap { translatedText in
                return api
                    .fetch(text: translatedText)
                    .catchError { error in .just((error as? ModelError)?.errorLabel ?? error.localizedDescription) }
            }
    }
}

在初始化所有成员之前，闭包捕获了Swift5（+ RxSwift）'self'

3 个答案: