Reactive cocoa forcing a synchronous function to wait for reactive callback

Question

I did a lot of research and haven't got any answer for this one.

this is my code:

fileprivate var dispose: ScopedDisposable<AnyDisposable>?    

func connectToServer() {
    ...
    let user = ...
    let channelName = getChannelName(user)
    self.connector.connectTo(channelName)
}

func getChannelName(_ user: String) -> String {
    var channelName: String = ""
    self.dispose = ScopedDisposable(
        self.service.requestChannelNameFromServerForUser(user)
        .startWithValues({ results in
            channelName = results[0].channelName
        })
    )
    return channelName // this will return "" because callback hasn't returned yet
}

I'm trying to find a way to make the function "getChannelName" to wait until "channelName" is retrieved from the reactive request (from another server).

Thanks for your help.

jjoelson · Accepted Answer · 2018-10-01T12:13:31.293

The first() function will essentially do this for you:

func getChannelName(_ user: String) -> String {
    let result = self.service.requestChannelNameFromServerForUser(user).first()
    if let results = result?.value {
        return results[0].channelName
    }
    else {
        // The producer returned no values or an error. Return a default value or throw error or something.
        return ""
    }
}

But the more idiomatic way to do this is to make connectToServer itself an asynchronous SignalProducer which connects the getChannelName and connectTo producers into one one larger producer.

Thank you very much! Will try that. – B.B. Oct 04 '18 at 08:01 — B.B., Oct 04 '18 at 08:01

Reactive cocoa forcing a synchronous function to wait for reactive callback

1 Answers1