iOS UIViewController extension to fix keyboard overriding textfield

UIViewController+UITextfield.swift

//
//  UIViewController+ext.swift
//  Antony Alkmim
//
//  Created by Antony Alkmim on 03/07/18.
//  Copyright © 2018 Antony Alkmim. All rights reserved.
//

import UIKit

/// stored dataKeys
private var activeFieldAssocKey = 0
private var scrollViewAssocKey = 0

// MARK: - UITextFieldDelegate
extension UIViewController: UITextFieldDelegate {
    public var activeField: UITextField? {
        get { return objc_getAssociatedObject(self, &activeFieldAssocKey) as? UITextField }
        set { objc_setAssociatedObject(self, &activeFieldAssocKey, newValue, objc_AssociationPolicy.OBJC_ASSOCIATION_RETAIN) }
    }

    public func textFieldDidEndEditing(textField: UITextField) {
        self.activeField = nil
    }

    public func textFieldShouldBeginEditing(_ textField: UITextField) -> Bool {
        self.activeField = textField
        return true
    }

    public func textFieldShouldReturn(textField: UITextField) -> Bool {
        guard let nextResponder = self.view.viewWithTag(textField.tag + 1) else {
            textField.resignFirstResponder()
            return false
        }

        nextResponder.becomeFirstResponder()
        return false
    }

    override open func touchesBegan(_ touches: Set<UITouch>, with event: UIEvent?) {
        self.view.endEditing(true)
    }

}

// MARK: - UIScrollViewDelegate
extension UIViewController: UIScrollViewDelegate {

    @IBOutlet var scrollView: UIScrollView? {
        get { return objc_getAssociatedObject(self, &scrollViewAssocKey) as? UIScrollView }
        set { objc_setAssociatedObject(self, &scrollViewAssocKey, newValue, objc_AssociationPolicy.OBJC_ASSOCIATION_RETAIN) }
    }

    @objc func keyboardWillShow(notification: NSNotification) {
        // Check if scrollView its referencied
        guard self.scrollView != nil else { return }

        if let activeField = self.activeField, let keyboardSize = (notification.userInfo?[UIKeyboardFrameBeginUserInfoKey] as? NSValue)?.cgRectValue {
            let contentInsets = UIEdgeInsets(top: 0.0, left: 0.0, bottom: keyboardSize.height, right: 0.0)
            self.scrollView!.contentInset = contentInsets
            self.scrollView!.scrollIndicatorInsets = contentInsets
            var aRect = self.view.frame
            aRect.size.height -= keyboardSize.size.height //subtract keyboard height

            if !aRect.contains(activeField.frame.origin) {
                self.scrollView!.scrollRectToVisible(activeField.frame, animated: true)
            }
        }
    }

    @objc func keyboardWillBeHidden(notification: NSNotification) {
        guard self.scrollView != nil else {return}

        UIView.animate(withDuration: 0.17) {
            self.scrollView!.contentInset = UIEdgeInsets.zero
            self.scrollView!.scrollIndicatorInsets = UIEdgeInsets.zero
            self.scrollView!.layoutIfNeeded()
        }
    }

    func setupScrollKeyboard() {
        NotificationCenter.default.addObserver(self,
                           selector: #selector(self.keyboardWillShow),
                           name: NSNotification.Name.UIKeyboardDidShow,
                           object: nil)
        NotificationCenter.default.addObserver(self,
                           selector: #selector(self.keyboardWillBeHidden),
                           name: NSNotification.Name.UIKeyboardDidHide,
                           object: nil)
    }
}

extension UIScrollView {
    override open func touchesBegan(_ touches: Set<UITouch>, with event: UIEvent?) {
        self.endEditing(true)
    }
}

ViewController.swift

import UIKit

class ViewController: UIViewController {

    // MARK: - Outlets

    @IBOutlet weak var textfield: UITextField!

    override func viewDidLoad() {
        super.viewDidLoad()
        
        textfield.delegate = self
        setupScrollKeyboard()
        textfield.becomeFirstResponder()
    }

}