concatExample.swift

import RxSwift

let disposeBag = DisposeBag()

let oldXmenMovies = Observable.of("X-Men", "X-Men United", "The Last Stand")
let newXmenMovies = Observable.of("First Class", "Days of Future Past", "Apocalypse")

oldXmenMovies.concat(newXmenMovies)
  .subscribe(onNext: { movie in
    print(movie)
  })
  .disposed(by: disposeBag)

// Output:
// X-Men
// X-Men United
// The Last Stand
// First Class
// Days of Future Past
// Apocalypse