enable button with RxSwift logic - ios

Question

I'm new to RxSwift and want to achieve the following. I have a email and password TextField. When you've entered a text in both textfields a button should be enabled.
In my ViewController I do the following:
txtEmail.rx.text.asObservable()
.bindTo(viewModel.email)
.addDisposableTo(disposeBag)
txtPassword.rx.text.asObservable()
.bindTo(viewModel.password)
.addDisposableTo(disposeBag)
viewModel.buttonEnabled
.bindTo(btnLogin.rx.isEnabled)
.addDisposableTo(disposeBag)
And here is my ViewModel:
import Foundation
import RxSwift
import RxCocoa
class LoginViewModel {
let email = Variable<String?>("")
let password = Variable<String?>("")
var buttonEnabled: Observable<Bool>
init() {
var processedEmail: Observable<String>!
var processedPassword: Observable<String>!
processedEmail = email.asObservable().map(String.toLower as! (String?) -> String).map(String.trimWhiteSpace as! (String?) -> String)
processedPassword = password.asObservable().map(String.toLower as! (String?) -> String).map(String.trimWhiteSpace as! (String?) -> String)
let emailValid = processedEmail.asObservable().map(String.isNotEmpty)
let passwordValid = processedPassword.asObservable().map(String.isNotEmpty)
buttonEnabled = Observable.combineLatest(emailValid, passwordValid) {
return $0 && $1
}
}
func didTapLoginButton() {
print("hello \(email.value)")
}
}
For some reason the init method of my viewmodel never gets finished.
Can someone help me?

Answer 1

It seems like the definition of processedEmail and processedPassword are generating the crash preventing the view model init to complete.
More specifically, the String.toLower and String.trimWhiteSpace method probably have type (String) -> String but here they are force cast to (String?) -> String.
processedEmail = email.asObservable()
.map { $0 ?? "" }
.map(String.toLower)
.map(String.trimWhiteSpace)
processedPassword = password.asObservable()
.map { $0 ?? "" }
.map(String.toLower)
.map(String.trimWhiteSpace)
I've only added .map { $0 ?? "" }. Because the original observable has type Observable<String?> the map call will transform it to Observable<String> which will then be processable by String.toLower and String.trimWhiteSpace

Answer 2

I tried this example of init and it seems working:
init() {
let processedEmail = email.asObservable()
.map { $0 ?? "" }
.map { $0.lowercased() }
.map { !$0.isEmpty }
let processedPassword = password.asObservable()
.map { $0 ?? "" }
.map { $0.trimmingCharacters(in: CharacterSet.whitespacesAndNewlines) }
.map { !$0.isEmpty }
buttonEnabled = Observable.combineLatest(processedEmail, processedPassword) {
return $0 && $1
}
}