Simple string formatter based on mask string

StringMaskr.swift

//
//  StringMask.swift
//  StringMask
//
//  Created by Jan Cássio on 8/19/16.
//  Copyright © 2016 Jan Cassio. All rights reserved.
//

import Foundation


enum StringMaskr {
    case CPF
    case Phone
    
    func mask () -> String {
        switch self {
        case .CPF:
            return "***.***.***-**"
            
        case .Phone:
            return "(**) *****-****"
            
        }
    }
    
    func placeholder () -> String {
        return "*"
    }
}

extension String {
    func formatWithMask (mask stringMask: StringMaskr) -> String {
        let mask = stringMask.mask()
        let placeholderChar = stringMask.placeholder()
        
        var result = ""
        
        if self.characters.count > 0 {
            let tempString = self.makeOnlyDigitsString()
            var formatterIndex = mask.startIndex
            var tempIndex = tempString.startIndex
            var stop = false
            
            while !stop {
                let formatterRange = formatterIndex..<formatterIndex.advancedBy(1)
                
                let currentChar = "\(mask.substringWithRange(formatterRange))"
                
                if currentChar != placeholderChar {
                    result += currentChar
                }
                else if tempString.characters.count > 0 {
                    let stringRange = tempIndex..<tempIndex.advancedBy(1)
                    result += tempString.substringWithRange(stringRange)
                    tempIndex = tempIndex.advancedBy(1)
                }
                
                formatterIndex = formatterIndex.advancedBy(1)
                
                stop = formatterIndex >= mask.endIndex || tempIndex >= tempString.endIndex
            }
        }
        
        return result
    }
    
    func makeOnlyDigitsString() -> String {
        return self.componentsSeparatedByCharactersInSet(
            NSCharacterSet.decimalDigitCharacterSet().invertedSet
            ).joinWithSeparator("")
    }
}