A simple UIViewController subclass that avoids the keyboard automatically.

KeyboardAvoidingViewController.swift

import UIKit

class KeyboardAvoidingViewController: UIViewController {
    
    private let margin: CGFloat = 20
    private var keyboardFrame: CGRect?

    override func viewDidLoad() {
        super.viewDidLoad()
        
        NotificationCenter.default.addObserver(self,
                                               selector: #selector(adjustForKeyboard),
                                               name: UIResponder.keyboardWillHideNotification,
                                               object: nil)
        NotificationCenter.default.addObserver(self,
                                               selector: #selector(adjustForKeyboard),
                                               name: UIResponder.keyboardWillChangeFrameNotification,
                                               object: nil)
    }
    
    @objc
    private func adjustForKeyboard(notification: Notification) {
        guard notification.name != UIResponder.keyboardWillHideNotification else {
            keyboardFrame = nil
            view.frame.origin.y = 0
            NotificationCenter.default.removeObserver(self, name: UITextView.textDidChangeNotification, object: nil)
            return
        }
        
        guard let keyboardValue = notification.userInfo?[UIResponder.keyboardFrameEndUserInfoKey] as? NSValue,
              let keyboardAnimationDuration = notification.userInfo?[UIResponder.keyboardAnimationDurationUserInfoKey] as? Float,
              let firstResponder = (UIResponder.firstResponder as? UIView)
        else { return }
        
        let firstResponderFrame: CGRect
        if let textView = firstResponder as? UITextView, let caretPosition = textView.selectedTextRange?.start {
            NotificationCenter.default.addObserver(self,
                                                   selector: #selector(adjustForTextViewCaret(_:)),
                                                   name: UITextView.textDidChangeNotification,
                                                   object: textView)
            firstResponderFrame = view.convert(textView.caretRect(for: caretPosition), from: firstResponder)
        } else {
            firstResponderFrame = view.convert(firstResponder.frame, from: firstResponder.superview)
        }
        
        keyboardFrame = view.convert(keyboardValue.cgRectValue, from: view.window)
        let offset = (firstResponderFrame.maxY - keyboardFrame!.minY) + margin - view.frame.origin.y
        if keyboardAnimationDuration > 0 && offset > 0 {
            // Animated implicitly with the keyboard.
            view.frame.origin.y = -offset
        } else {
            // Wrap inside an animation block as there is no keyboard animation (jumping between text fields).
            UIView.animate(withDuration: 0.25, delay: 0, options: .curveEaseOut, animations: {
                if offset > 0 {
                    self.view.frame.origin.y = -offset
                }
            })
        }
    }
    
    @objc
    private func adjustForTextViewCaret(_ notification: NSNotification) {
        guard let textView = notification.object as? UITextView,
              let keyboardFrame = keyboardFrame,
                let caretPosition = textView.selectedTextRange?.start else {
            return
        }
        
        let caretFrame = view.convert(textView.caretRect(for: caretPosition), from: textView)
        let offset = (caretFrame.maxY - keyboardFrame.minY) + margin
        UIView.animate(withDuration: 0.25, delay: 0, options: .curveEaseOut, animations: {
            if offset > 0 {
                self.view.frame.origin.y = -offset
            }
        })
    }
}

private extension UIResponder {
    
    private static weak var _firstResponder: UIResponder?
    
    static var firstResponder: UIResponder? {
        _firstResponder = nil
        UIApplication.shared.sendAction(#selector(UIResponder.findFirstResponder(_:)), to: nil, from: nil, for: nil)
        return _firstResponder
    }

    @objc
    private func findFirstResponder(_ sender: Any) {
        UIResponder._firstResponder = self
    }
}