Phone Number - OneTimePassword Inputview design code and the fancy here is cursor going forward and backward is awesome.

One Time Password View.swift

import UIKit

protocol OTPInputViewProtocol:class {
    func digitsInputViewCompletion()
}

fileprivate let MAX_COUNT_DOWN_TIME:Int = 120

class ADOTPInputView: UIView,UITextFieldDelegate {
    
    @IBOutlet weak var digit1: DigitTextField!
    @IBOutlet weak var digit2: DigitTextField!
    @IBOutlet weak var digit3: DigitTextField!
    @IBOutlet weak var digit4: DigitTextField!
    @IBOutlet weak var countDownView: UIView!
    
    private var timer:Timer?
    private var max_Time = MAX_COUNT_DOWN_TIME
    
    public weak var delegate:OTPInputViewProtocol?
    
    //MARK: - Custom Getters and Setters
    lazy var countDownLabel: UILabel = {
        let label = UILabel()
        label.frame = CGRect(x:0,y:0,width:self.countDownView.frame.width,height:self.countDownView.frame.height)
        label.font = Utilities.appThemeLightFontWithSize(size: 14)
        label.textColor = UIColor.rgb(fromHex: 0x6A1B9A)
        label.text = "2:00"
        label.textAlignment = .center
        label.addKernAttribute()
        label.addGestureRecognizer(self.tapper)
        return label
    }()
    
    lazy var tapper: UITapGestureRecognizer = {
        let tapGesture = UITapGestureRecognizer.init(target: self, action: #selector(startOTPTimer))
        tapGesture.numberOfTapsRequired = 1
        return tapGesture
    }()
    
    // if appropriate, make sure to stop your timer in `deinit`
    deinit {
        stopTimer()
    }
    
    //MARK: - Public functions
    public func startOTPTimer() {
        self.countDownLabel.isUserInteractionEnabled = false
        self.timer = Timer.scheduledTimer(timeInterval: 0.25, target: self, selector: #selector(self.update), userInfo: nil, repeats: true)
    }
    
    public func stopTimer() {
        timer?.invalidate()
    }
    
    public func initalViewSetup() {
        self.digit1.delegate = self
        self.digit2.delegate = self
        self.digit3.delegate = self
        self.digit4.delegate = self
        
        self.digit1.addTarget(self, action: #selector(textFieldDidChange), for: UIControlEvents.editingChanged)
        self.digit2.addTarget(self, action: #selector(textFieldDidChange), for: UIControlEvents.editingChanged)
        self.digit3.addTarget(self, action: #selector(textFieldDidChange), for: UIControlEvents.editingChanged)
        self.digit4.addTarget(self, action: #selector(textFieldDidChange), for: UIControlEvents.editingChanged)
        
        self.digit1.becomeFirstResponder()
        self.digit2.isEnabled = false
        self.digit3.isEnabled = false
        self.digit4.isEnabled = false
        
        self.countDownView.addSubview(countDownLabel)
        
        NotificationCenter.default.addObserver(self, selector: #selector(gotoPreviousDigits), name: NSNotification.Name(rawValue: "deletePressed"), object: nil)
        
    }
    
    //MARK: - Private functions
    @objc private func update() {
        max_Time -= 1
        if(max_Time > 0){
            let minutes = String(max_Time / 60)
            let seconds = String(max_Time % 60)
            DispatchQueue.main.async {
                self.countDownLabel.text = minutes + " : " + seconds
            }
        }
        if max_Time == 1 {
            self.countDownLabel.isUserInteractionEnabled = true
            self.timer?.invalidate()
            self.max_Time = MAX_COUNT_DOWN_TIME
            DispatchQueue.main.async {
                self.countDownLabel.attributedText = self.attributedString(from: "Time elapsed. Resend code", resendCodeColorRange: NSMakeRange(0, 13))
            }
        }
    }
    
    //MARK: - Private functions
    private func attributedString(from string: String, resendCodeColorRange: NSRange?) -> NSAttributedString {
        let attrs = [
            NSForegroundColorAttributeName:self.countDownLabel.textColor
        ]
        let blackColorAttr = [
            NSForegroundColorAttributeName: UIColor.rgb(fromHex: 0x2D4059),
            ]
        let attrStr = NSMutableAttributedString(string: string, attributes: attrs)
        
        attrStr.setAttributes(blackColorAttr, range: resendCodeColorRange!)
        return attrStr
    }
    
    //MARK: - UITextField Delegates
    func textFieldDidChange(textField: UITextField){
        
        let text = textField.text
        
        if text?.utf16.count==1{
            switch textField{
            case self.digit1:
                self.digit2.isEnabled = true
                self.digit2.becomeFirstResponder()
            case self.digit2:
                self.digit3.isEnabled = true
                self.digit3.becomeFirstResponder()
            case self.digit3:
                self.digit4.isEnabled = true
                self.digit4.becomeFirstResponder()
            case self.digit4:
                self.digit4.isEnabled = false
                self.digit4.resignFirstResponder()
                self.delegate?.digitsInputViewCompletion()
            default:
                break
            }
        }else{
            
        }
    }
    
    //MARK: - Observers
    func gotoPreviousDigits() {
        if digit2.isFirstResponder {
            digit2.isEnabled = false
            digit1.isEnabled = true
            digit1.becomeFirstResponder()
        } else if digit3.isFirstResponder {
            digit3.isEnabled = false
            digit2.isEnabled = true
            digit2.becomeFirstResponder()
        } else if digit4.isFirstResponder {
            digit4.isEnabled = false
            digit3.isEnabled = true
            digit3.becomeFirstResponder()
        }
    }
}


class DigitTextField: UITextField {
    
    override func deleteBackward() {
        super.deleteBackward()
        NotificationCenter.default.post(name: Notification.Name(rawValue: "deletePressed"), object: nil)
    }
    
}