Pausable.swift

extension ObservableType {

    /// Pauses the elements of the source observable sequence based on
    /// the latest element from the second observable sequence.
    /// Elements are ignored unless the second sequence has most recently
    /// emitted `true`.
    /// - Parameter pauser: The observable sequence used to pause the source
    /// observable sequence.
    /// - Returns: The observable sequence which is paused based upon
    /// the pauser observable sequence.
    public func pausable<P: ObservableType> ( _ pauser: P) -> Observable<E>
                                                              where P.E == Bool {
        return withLatestFrom(pauser) { element, paused in
            (element, paused)
            }.filter { _, paused in
                paused
            }.map { element, _ in
                element
        }
    }
}