Exemplo de máscara para CPF e CEP sem uso de dependência externa

cpfMask.swift

//
//  ViewController.swift
//  ProjetoPodTest
//
//  Created by Wesley Brito on 24/11/18.
//  Copyright © 2018 Wesley Brito. All rights reserved.
//

import UIKit

class ViewController: UIViewController {
    
    @IBOutlet weak var textField: UITextField!
    
    
    override func viewDidLoad() {
        super.viewDidLoad()
        // Do any additional setup after loading the view, typically from a nib.
        
    }


}

extension ViewController: UITextFieldDelegate {
    func textField(_ textField: UITextField, shouldChangeCharactersIn range: NSRange, replacementString string: String) -> Bool {
        var appendString = ""
        
        if textField.placeholder == "CPF" {
            if range.length == 0 {
                switch range.location {
                case 3:
                    appendString = "."
                case 7:
                    appendString = "."
                case 11:
                    appendString = "-"
                default:
                    break
                }
            }
            
            textField.text?.append(appendString)
            
            if (textField.text?.count)! > 13 && range.length == 0 {
                return false
            }
        } else if textField.placeholder == "CEP" {
            if range.length == 0 {
                switch range.location {
                case 2:
                    appendString = "."
                case 6:
                    appendString = "-"
                default:
                    break
                }
            }
            
            textField.text?.append(appendString)
            
            if (textField.text?.count)! > 9 && range.length == 0 {
                return false
            }
        }
        return true
    }
    
}