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import RxSwift
import RxCocoa

final class Toggle {

    // MARK: - Properties

    private let storage: ToggleStorage

    // MARK: - Initializer

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enum ToggleValue {

    /// Initial value read from storage
    case initial(Bool)

    /// Updated value after successfully saving in storage
    case updated(Bool)

    /// Fallback value after unsuccessfully saving in storage
    case fallback(Bool)

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func manage(change: Observable<Bool>) -> (value: Driver<ToggleValue>, isBusy: Driver<Bool>) {
    // ...

    let initialValue = storage
        .read()
        .map { ToggleValue.initial($0) }
        .catchError { Observable.just( ToggleValue.unknown($0) ) }

    // ...
}

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func manage(change: Observable<Bool>) -> (value: Driver<ToggleValue>, isBusy: Driver<Bool>) {
    // ...
  
    let storage = self.storage
  
    let valueAfterSaving = change
        .flatMap { valueToSave -> Observable<ToggleValue> in
            storage
                .save(value: valueToSave)
                .map { ToggleValue.updated(valueToSave) }

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func manage(change: Observable<Bool>) -> (value: Driver<ToggleValue>, isBusy: Driver<Bool>) {
    let storage = self.storage

    let initialValue = storage
        .read()
        .map { ToggleValue.initial($0) }
        .catchError { Observable.just( ToggleValue.unknown($0) ) }

    let valueAfterSaving = change
        .flatMap { valueToSave -> Observable<ToggleValue> in

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func manage(change: Observable<Bool>) -> (value: Driver<ToggleValue>, isBusy: Driver<Bool>) {
    let storage = self.storage
    let isBusySubject = PublishSubject<Bool>()

    let isBusy = isBusySubject
        .asDriver(onErrorJustReturn: false)
        .startWith(true)

    let initialValue = storage
        .read()

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import UIKit
import RxCocoa
import RxSwift

class SettingsViewController: UIViewController {

    @IBOutlet weak var settingSwitch1: UISwitch!
    @IBOutlet weak var settingSwitch2: UISwitch!
    @IBOutlet weak var settingSwitch3: UISwitch!
    @IBOutlet weak var settingSwitch4: UISwitch!

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private func setUp(settingSwitch: UISwitch, with toggle: Toggle) {
    let (value, isBusy) = toggle.manage(change: settingSwitch.rx.isOn.changed.asObservable())

    let initialValue = value
        .filter { $0.isInitial }
        .map { $0.value }
        .flatMap { $0.map(Driver.just) ?? Driver.empty() } // .unwrap() if using `RxSwiftExt`

    let fallbackValue = value
        .filter { $0.isFallback }

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extension ToggleValue {
    var value: Bool? {
        switch self {
        case .initial(let value), .updated(let value), .fallback(let value):
            return value
        case .unknown:
            return nil
        }
    }

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private func setUp(settingSwitch: UISwitch, with toggle: Toggle) {
    let (value, isBusy) = toggle.manage(change: settingSwitch.rx.isOn.changed.asObservable())

    // ...

    let isSwitchDisabled = isBusy
        .map { !$0 }

    isSwitchDisabled
        .drive(settingSwitch.rx.isEnabled)