"withLatestFrom" won't accept BehaviorRelay - swift

Question

I've got this simple view model to check a phone number's status before registering a user. But I've got this error:
Instance method 'withLatestFrom' requires that 'BehaviorRelay' conform to 'SharedSequenceConvertibleType'
Here's the code:
import Foundation
import RxSwift
import RxCocoa
protocol RegisterViewModelling {
var openRegistrationData: Signal<String> { get }
var showErrorMessage: Signal<String> { get }
var sendButtonActive: Driver<Bool> { get }
var phoneNumberText: BehaviorRelay<String> { get }
var tapSendButton: PublishRelay<Void> { get }
}
final class RegisterViewModel: RegisterViewModelling {
var openRegistrationData: Signal<String>
let showErrorMessage: Signal<String>
let sendButtonActive: Driver<Bool>
let phoneNumberText: BehaviorRelay<String> = BehaviorRelay<String>(value: "")
let tapSendButton: PublishRelay<Void> = PublishRelay<Void>()
init(getPhoneNumberStatus: GetPhoneNumberStatusUseCase) {
sendButtonActive = phoneNumberText
.asDriver(onErrorDriveWith: .empty())
.map(shouldButtonActive(number:))
let isRegistered = tapSendButton
.withLatestFrom(phoneNumberText)
.flatMap(getPhoneNumberStatus.get(number:))
.share()
showErrorMessage = isRegistered
.asSignal(onErrorSignalWith: .just(true))
.filter { $0 == true }
.map { _ in () }
.map(getErrorMessage)
openRegistrationData = isRegistered
.asSignal(onErrorSignalWith: .just(true))
.filter { $0 == false }
.withLatestFrom(phoneNumberText) // ERROR: Instance method 'withLatestFrom' requires that 'BehaviorRelay<String>' conform to 'SharedSequenceConvertibleType'
}
}
private func shouldButtonActive(number: String) -> Bool {
return !number.isEmpty && number.count <= 15
}
private func getErrorMessage() -> String {
return "Phone number has been registered."
}
protocol GetPhoneNumberStatusUseCase {
func get(number: String) -> Observable<Bool>
}
What went wrong here? Why won't withLatestFrom work at that line but it worked fine on the others? Thanks.

Answer 1

I think it because you have convert isRegistered to Signal before use withLatestFrom. You can try to move asSignal() to below withLatestFrom