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.

Answer 1

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.