如何获取 UIAlertController 可观察对象（ReactiveCocoa 或 RxSwift）？

Question

我实现了一个“反应式”UIAlertController，所以我可以得到一个按下按钮的Observable<Int>。 （见下面的代码）。

我的一个或多个问题是：

• 这个实现是否正确？我不喜欢存储观察者；我想知道是否有更好的解决方案。
• 或者...是否已经在 ReactiveCocoa 或 RxSwift 中实现了此功能？

这里是实现。我删除了与问题无关的部分。

class AlertBuilder {

    typealias AlertAction = (Int) -> ()

    private let alert: UIAlertController

    /** If observable() is called, we keep here the observers to notify them */
    private var observers: [AnyObserver<Int>] = []

    init(alert: UIAlertController) {
        self.alert = alert
    }

    /** When using observable(), the action is not needed. */
    func button(_ title: String, style: UIAlertActionStyle = .default, action: AlertAction? = nil) -> AlertBuilder {

        let buttonIndex = alert.actions.count
        alert.addAction( UIAlertAction(title: title, style: style, handler: { [weak self] _ in

            // Callback via action
            action?(buttonIndex)

            // Callback via observers
            if let this = self {
                for observer in this.observers {
                    observer.onNext(buttonIndex)
                    observer.onCompleted()
                }
                this.observers = []
            }
        }) )
        return self
    }

    /**
     * Returns an Observable that will emit the pressed button index and complete.
     * It's important to keep a reference to the AlertBuilder, otherwise the events won't be received.
     */
    func observable() -> Observable<Int> {

        return Observable<Int>.create { observer in
            self.observers.append(observer)
            return Disposables.create()
        }
    }
}

您可以从控制器中使用它，如下所示：

let alert = UIAlertController(title: "title", message: "msg", preferredStyle: .actionSheet)

let builder = AlertBuilder(alert: alert)
    .button("no", style: .destructive)
    .button("yes")

self.present(alert, animated: true, completion: nil)

self.builder.observable()
    .subscribe(onNext: { buttonIndex in /* ... */ })
    .disposed(by: bag)

// keep reference to builder so observable() works
self.builder = builder

Answer 1

你可以使用这个UIAlert-RxSwift， 这是一个Rx 扩展

Answer 2

我正在寻找一种以响应式方式使用 AlertController 的好方法，这篇文章对我有帮助。

我使用了 Pacification 的解决方案，但我必须对其进行更新才能返回通用值而不是索引。我还调整了 swift 4 的语法。

我把它贴在这里以防有人感兴趣。

extension UIAlertController {
  struct Action<T> {
    var title: String?
    var style: UIAlertAction.Style
    var value: T

    static func action(title: String?, style: UIAlertAction.Style = .default, value: T) -> Action {
      return Action(title: title, style: style, value: value)
    }
  }

  static func present<T>(in viewController: UIViewController,
                      title: String? = nil,
                      message: String? = nil,
                      style: UIAlertController.Style,
                      actions: [Action<T>]) -> Observable<T> {
    return Observable.create { observer in
      let alertController = UIAlertController(title: title, message: message, preferredStyle: style)

      actions.enumerated().forEach { index, action in
        let action = UIAlertAction(title: action.title, style: action.style) { _ in
          observer.onNext(action.value)
          observer.onCompleted()
        }
        alertController.addAction(action)
      }

      viewController.present(alertController, animated: true, completion: nil)
      return Disposables.create { alertController.dismiss(animated: true, completion: nil) }
    }
  }
}

问候

Answer 3

允许将所有代码保存在一个位置的解决方案是extension 到UIAlertViewController：

extension UIAlertController {

    struct AlertAction {
        var title: String?
        var style: UIAlertActionStyle

        static func action(title: String?, style: UIAlertActionStyle = .default) -> AlertAction {
            return AlertAction(title: title, style: style)
        }
    }

    static func present(
        in viewController: UIViewController,
        title: String?, 
        message: String?,
        style: UIAlertControllerStyle,
        actions: [AlertAction])
        -> Observable<Int>
    {
        return Observable.create { observer in
            let alertController = UIAlertController(title: title, message: message, preferredStyle: style)

            actions.enumerated().forEach { index, action in
                let action = UIAlertAction(title: action.title, style: action.style) { _ in
                    observer.onNext(index)
                    observer.onCompleted()
                }
                alertController.addAction(action)
            }

            viewController.present(alertController, animated: true, completion: nil)
            return Disposables.create { alertController.dismiss(animated: true, completion: nil) }
        }

    }

}

及用法：

let actions: [UIAlertController.AlertAction] = [
    .action(title: "no", style: .destructive),
    .action(title: "yes")
]

UIAlertController
    .present(in: self, title: "Alert", message: "message", style: .alert, actions: actions)
    .subscribe(onNext: { buttonIndex in
        print(buttonIndex)
    })
    .disposed(by: bag)

代码和逻辑非常简单，所以我在这里不做解释。如果您有任何问题，请询问。