Setting up keyboard notifications and responding to their actions

ManagingKeyboard.swift

//
//  ViewController.swift
//  KeyboardHandling
//
//  Created by Alex Paul on 1/29/19.
//  Copyright © 2019 Alex Paul. All rights reserved.
//

import UIKit

class ViewController: UIViewController {
  
  @IBOutlet weak var containerView: UIView!
  @IBOutlet weak var usernameTextField: UITextField!
  @IBOutlet weak var passwordTextField: UITextField!
  
  override func viewDidLoad() {
    super.viewDidLoad()
    registerForKeyboardNotifications()
  }
  
  private func registerForKeyboardNotifications() {
    NotificationCenter.default.addObserver(self, selector: #selector(keyboardWillShow), name: UIResponder.keyboardWillShowNotification, object: nil)
    NotificationCenter.default.addObserver(self, selector: #selector(keyboardWillHide), name: UIResponder.keyboardWillHideNotification, object: nil)
  }
  
  private func unregisterForKeyboardNotifications() {
    NotificationCenter.default.removeObserver(self, name: UIResponder.keyboardWillShowNotification, object: nil)
    NotificationCenter.default.removeObserver(self, name: UIResponder.keyboardWillHideNotification, object: nil)
  }
  
  override func viewWillDisappear(_ animated: Bool) {
    super.viewWillDisappear(true)
    unregisterForKeyboardNotifications()
  }
  
  @objc private func keyboardWillShow(notification: NSNotification) {
    guard let info = notification.userInfo,
      let frame = info["UIKeyboardFrameEndUserInfoKey"] as? CGRect else {
      return
    }
    print(info) // prints keys in info dictionary e.g UIKeyboardFrameEndUserInfoKey
    containerView.transform = CGAffineTransform(translationX: 0, y: -frame.height)
  }
  
  @objc private func keyboardWillHide(notification: NSNotification) {
    containerView.transform = CGAffineTransform.identity
  }
  
  @IBAction func loginButtonPressed(_ sender: UIButton) {
    usernameTextField.resignFirstResponder()
    passwordTextField.resignFirstResponder()
  }
}