How can I create SignIn and SignOut with 1 button in RxSwift? - mvvm

Question

Here my code to change text in button:
func transform(input: Input) -> Output {
let tappedSigninCheck = input.signinTrigger
.scan(false) { lastState, _ in
return !lastState }
let singupButtonTitle = tappedSigninCheck.map {
return $0 == true ? "Sign Out" : "Sign In"
}
return Output(signinButtonTitle: singupButtonTitle)
}
Now when I clicked SignIn, button text will change to "Sign Out" and I want when click Sign Out, sign out will display 1 alert and when click Yes in alert then button text change to Sign In.
My problem: whenever I click in button then button text change text :(((
func bindViewModel() {
let signoutTrigger = signinButton.rx.tap.flatMap {
return Observable<Void>.create { (observer) -> Disposable in
let alert = UIAlertController(title: "Are you sure to sign out?",
message: nil,
preferredStyle: .alert)
alert.addAction(UIAlertAction(title: "No",
style: .cancel,
handler: nil))
alert.addAction(UIAlertAction(title: "Yes",
style: .destructive,
handler: { _ in
observer.onNext(Void())
}))
self.present(alert, animated: true)
return Disposables.create()
}
}
let input = ProfileViewModel.Input(signinTrigger: signinButton.rx.tap.asDriver(),
signoutTrigger: signoutTrigger.asDriver(onErrorJustReturn: Void()))
let output = profileViewModel.transform(input: input)
output
.signinButtonTitle
.drive(signinButton.rx.title)
.disposed(by: disposeBag)
}

Answer 1

For this you will need a feedback loop, and that calls for a Subject. I suggest you do it something like below. Also note that you forgot to emit a completed event on your alert.:
class ViewModel {
struct Input {
let logButton: Observable<Void>
let okayButton: Observable<Void>
}
struct Output {
let buttonTitle: Observable<String>
let displayAlert: Observable<Void>
}
private enum Action {
case tapped
case okay
}
private enum State {
case offline
case online
case check
}
func transform(_ input: Input) -> Output {
let state = Observable.merge(
input.logButton.map(to: ViewModel.Action.tapped),
input.okayButton.map(to: ViewModel.Action.okay)
)
.scan(ViewModel.State.offline) { state, action in
switch (state, action) {
case (.offline, .tapped):
return .online
case (.online, .tapped):
return .check
case (.check, .okay):
return .offline
case (.check, .tapped):
return .check
default:
assert(false)
return state
}
}
.share()
let buttonTitle = state
.map { $0 == .offline ? "Log In" : "Log Out" }
let displayAlert = state
.filter { $0 == .check }
.map(to: ())
return Output(
buttonTitle: buttonTitle,
displayAlert: displayAlert
)
}
}
class ViewController: UIViewController {
var button: UIButton!
var viewModoel: ViewModel!
let disposeBag = DisposeBag()
func bind() {
let logout = PublishSubject<Void>()
let input = ViewModel.Input(
logButton: button.rx.tap.asObservable(),
okayButton: logout
)
let output = viewModoel.transform(input)
output.buttonTitle
.bind(to: button.rx.title(for: .normal))
.disposed(by: disposeBag)
output.displayAlert
.flatMap { [unowned self] _ in
self.areYouSure()
}
.bind(to: logout)
.disposed(by: disposeBag)
}
func areYouSure() -> Observable<Void> {
Observable.create { [unowned self] observer in
let alert = UIAlertController(
title: "Are you sure to sign out?",
message: nil,
preferredStyle: .alert
)
alert.addAction(UIAlertAction(
title: "Yes", style: .destructive, handler: { _ in
observer.onNext(())
observer.onCompleted()
}
))
alert.addAction(UIAlertAction(
title: "No", style: .default, handler: { _ in
observer.onCompleted()
}
))
self.present(alert, animated: true)
return Disposables.create()
}
}
}