RxSwift: Two UITextView text count.

ViewController.swift

import UIKit
import RxSwift
import RxCocoa

class ViewController: UIViewController {

    @IBOutlet weak var textView: UITextView!
    @IBOutlet weak var countLabel: UILabel!
    
    @IBOutlet weak var textView2: UITextView!
    @IBOutlet weak var countLabel2: UILabel!
    
    let disposeBag = DisposeBag()
    
    override func viewDidLoad() {
        super.viewDidLoad()

        // textView
        textViewCountObservable(textView)
            .bindTo(countLabel.rx_text)
            .addDisposableTo(disposeBag)
        
        // textView2
        textViewCountObservable(textView2)
            .bindTo(countLabel2.rx_text)
            .addDisposableTo(disposeBag)
    }
    
    /**
     指定されたTextViewの初期表示・内容の変更時に、入力されている文字数のテキストが流れるObservable.
     ex) "hello" -> "count: 5"
     
     - parameter textView: textView
     
     - returns: Observable
     */
    func textViewCountObservable(textView: UITextView) -> Observable<String> {
        return NSNotificationCenter.defaultCenter()
                .rx_notification(UITextViewTextDidChangeNotification, object: textView)
                .startWith(NSNotification(name: "start", object: nil))
                .map{ _ -> String in
                    let count: Int = textView.text?.characters.count ?? 0
                    return "count: \(count)"
                }
    }
}