RxComplexApi.swift

func getPost() -> Observable<Post> {
    let postRef = Database.database().reference()
        .child("posts")
    return postRef.rx_observeEvent(event: .childAdded)
        .map { Post(snapshot: $0) }
        .unwrap()
}

getPost()
//It will emit an Error Event in case timed out 
.timeout(10, scheduler: MainScheduler.instance)
//Filter the result in one line
.filter { $0.title?.contains("QueryString") ?? false }
.subscribe()
.disposed(by: disposeBag)