RxSwift - Nofication sample

ViewController.swift

import UIKit
import RxSwift
import RxCocoa

class ViewController: UIViewController {

    @IBOutlet weak var textView: UITextView!
    @IBOutlet weak var countLabel: UILabel!
    
    let disposeBag = DisposeBag()
    
    override func viewDidLoad() {
        super.viewDidLoad()
        
        // Update char count label, when textview did change and first.
        
        NSNotificationCenter.defaultCenter()
            .rx_notification(UITextViewTextDidChangeNotification)
            .startWith(NSNotification(name: "startup", object: nil))
            .subscribeNext { [unowned self] _ in
                let count: Int = self.textView.text?.characters.count ?? 0
                self.countLabel.text = "count: \(count)"
            }
            .addDisposableTo(disposeBag)
    }
}