var singleEmissionStream: Observable<[Int]>!

// subscribe produce a two events:
1.next([1, 2, 3])
2.completed

func observeArray() {
    singleEmissionStream = Observable.just(numbersArray)
    singleEmissionStream.subscribe({
        array in
        print(array)
    })
    numbersArray.append(7)
    numbersArray.append(8)
}