Swift5(+RxSwift) 'self' 在所有成员初始化之前被闭包捕获

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 "translatedText" 的值，但错误仍然出现。

我已经尝试了一些用声明初始化的方法等等...


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？

-----自己解决-----

我只是在 let 事件之前简单地创建了一个临时变量，它按我的意愿工作。

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

您的问题是当您调用 flatMap 时 self 没有完全初始化。在您的情况下，validationText 和 getObservable 处于未定义状态。

最快的方法是让它们隐式解包可选值，但你真的必须保证它们在初始化之前不会被访问：

final class ViewModel {


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

    // ...
}

Answer 2

----自解-----

我只是简单地在 let 事件之前创建了一个临时变量，它按我的意愿工作。

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

你不应该用一些随机的 "temp" 内存块将两个独立的可观察流相互联系起来。这两个流依赖于 inputObservable，应该明确这一点。此外，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 { [=10=] }
            .flatMap { translatedText in
                return api
                    .fetch(text: translatedText)
                    .catchError { error in .just((error as? ModelError)?.errorLabel ?? error.localizedDescription) }
            }
    }
}

Swift5(+RxSwift) 'self' 在所有成员初始化之前被闭包捕获

Swift5(+RxSwift) 'self' captured by a closure before all members were initialized

xcode

swift

rx-swift