reactive cocoa migrate

let (refreshSignal, refreshObserver) = SignalProducer<InputType?, NoError>.buffer(2)
self.refreshSignal = refreshSignal
self.refreshObserver = refreshObserver

let (contentChangesSignal, contentChangesObserver) = Signal<OutputType, NoError>.pipe()
self.contentChangesSignal = contentChangesSignal
self.contentChangesObserver = contentChangesObserver

let (errorSignal, errorObserver) = Signal<NSError, NoError>.pipe()
self.errorSignal = errorSignal
self.errorObserver = errorObserver

if let trigger = lifetimeTrigger {
    viewLifetime.producer
        .filter { (lifetime:ViewLifetime) -> Bool in
            return lifetime == trigger
        }.map { _ in nil }
        .start(refreshObserver)
}

refreshSignal
    .flatMap(refreshFlattenStrategy) { (input) -> SignalProducer<OutputType, NoError> in

        let p = self.loadingProducerWithInput(input)
            .on(started: { self.isLoading.value = true }, terminated: { self.isLoading.value = false })
            .flatMapError({ (error) -> SignalProducer<OutputType, NoError> in
                self.errorObserver.sendNext(error)
                return SignalProducer.empty
            })

        return p
    }
    .observeOn(UIScheduler())
    .startWithNext { [weak self] (nextValue) in
        self?.loadedContent = nextValue
        if let obs = self?.contentChangesObserver {
            obs.sendNext(nextValue)
        }
}