RXSwift User input on error and continuation

Question

I'm quite new to RX and I'm trying to understand how I can continue a task, after an error which requires user input.

A concrete example would be two factor authentication.. We have an auth-service and a protected resource. Logging in, we receive from the auth-service a LOA-2 (username&password used) token. trying to fetch data from the protected resource we receive an error stating we need LOA-3 (two-factor). So we have to get the input from the user, send it to the auth-service, get a new token (LOA-3) und retry our fetch call with the new token.

There are a lot of examples for logins, but I can't wrap my head around continuing a chain, which requires user input.

Any ideas? Thanks :)

Daniel T. Daniel T. · Accepted Answer · 2016-07-13T02:26:22

You will need to use the catchError function to recover from the error and start a new observable that initiates the alternative behavior.

So for example, you need a producer that gets the username and password...

let credentialInput = Observable.combineLatest(usernameLabel.rx_text, passwordLabel.rx_text)

You will likely want to wait until the user taps a "login" button...

let credentials = credentialInput.sample(loginButton.rx_tap)

Then get the token.

let loaToken = credentials.flatMap { serverLogin($0, $1) }.catchError { error in 
    if error == loa3Error {
        return getLOA3Data().flatMap { loa3ServerLogin($0) }
    }
    else {
        throw error
    }
}

getLOA3Data is a function that returns an Observable that contains the data needed for the loa3 authentication.

The above is, of course, pseudo code, but I expect it will give you a good idea about how to wrap your head around the problem.

RXSwift User input on error and continuation

1 Answers