playingaround.swift

func fetchData(request: NSURLRequest) -> SignalProducer<[Foo], Error> {
    return foosFromServer(request).flatMapError {_ in //network failed deal with it}
     .flatMapLatest { parseFoos($0).flatMapError {_ in //parse failed deal with it} }
     .flatMapLatest { persistFoos($0).flatMapError {_ in //persist failed deal with it} }
     .flatMapError { error in loadFoosFromCache().mapError {_ in error} }
}