import RxSwift

// trick to get a clean unwrap optional by creating an intermediate type
protocol Optionable {
    associatedtype Wrapped
    var value: Wrapped? { get }
}

extension Optional : Optionable {
    var value: Wrapped? { return self  }
}

extension ObservableType where Self.E : Optionable {
    func flatten() -> Observable<Self.E.Wrapped> {
        return filter { $0.value != nil} .map { $0.value! }
    }
}