Formatting Phone number in Swift

Question

I\'m formatting my textfiled text once the user start typing the phone number into this format type 0 (555) 444 66 77 and it is working fine but once I get the

Answer 1

Swift 3 but should also be translatable to Swift 4

1. ErrorHandling

   enum PhoneNumberFormattingError: Error {
       case wrongCharactersInPhoneNumber
       case phoneNumberLongerThanPatternAllowes
   }
   

2. Create Patterns

   enum PhoneNumberFormattingPatterns: String {
       case mobile = "+xx (yxx) xxxxxxxxxxx"
       case home = "+xx (yxxx) xxxx-xxx"
   }
   

3. Insert Function

   /**
        Formats a phone-number to correct format
        - Parameter pattern: The pattern to format the phone-number.
        - Example:
           - x: Says that this should be a digit.
           - y: Says that this digit cannot be a "0".
           - The length of the pattern restricts also the length of allowed phone-number digits.
               - phone-number: "+4306641234567"
               - pattern: "+xx (yxx) xxxxxxxxxxx"
               - result: "+43 (664) 1234567"
   
        - Throws:
           - PhoneNumberFormattingError
               - wrongCharactersInPhoneNumber: if phone-number contains other characters than digits.
               - phoneNumberLongerThanPatternAllowes: if phone-number is longer than pattern allows.
        - Returns:
           - The formatted phone-number due to the pattern.
        */
   extension String {
       func vpToFormattedPhoneNumber(withPattern pattern: PhoneNumberFormattingPatterns) throws -> String {
           let phoneNumber = self.replacingOccurrences(of: "+", with: "")
           var retVal: String = ""
           var index = 0
           for char in pattern.rawValue.lowercased().characters {
               guard index < phoneNumber.characters.count else {
                   return retVal
               }
   
               if char == "x" {
                   let charIndex = phoneNumber.index(phoneNumber.startIndex, offsetBy: index)
                   let phoneChar = phoneNumber[charIndex]
                   guard "0"..."9" ~= phoneChar else {
                       throw PhoneNumberFormattingError.wrongCharactersInPhoneNumber
                   }
                   retVal.append(phoneChar)
                   index += 1
               } else if char == "y" {
                   var charIndex = phoneNumber.index(phoneNumber.startIndex, offsetBy: index)
                   var indexTemp = 1
                   while phoneNumber[charIndex] == "0" {
                       charIndex = phoneNumber.index(phoneNumber.startIndex, offsetBy: index + indexTemp)
                       indexTemp += 1
                   }
   
                   let phoneChar = phoneNumber[charIndex]
                   guard "0"..."9" ~= phoneChar else {
                       throw PhoneNumberFormattingError.wrongCharactersInPhoneNumber
                   }
                   retVal.append(phoneChar)
                   index += indexTemp
               } else {
                   retVal.append(char)
               }
           }
   
           if phoneNumber.endIndex > phoneNumber.index(phoneNumber.startIndex, offsetBy: index) {
               throw PhoneNumberFormattingError.phoneNumberLongerThanPatternAllowes
           }
   
           return retVal
       }
   }
   

4. Usage

   let phoneNumber = "+4306641234567"
   let phoneNumber2 = "4343211234567"
   
   do {
       print(try phoneNumber.vpToFormattedPhoneNumber(withPattern: .mobile))
       print(try phoneNumber2.vpToFormattedPhoneNumber(withPattern: .home))
   } catch let error as PhoneNumberFormattingError {
       switch error {
       case .wrongCharactersInPhoneNumber:
           print("wrong characters in phone number")
       case .phoneNumberLongerThanPatternAllowes:
           print("too long phone number")
       default:
           print("unknown error")
       }
   } catch {
       print("something other went wrong")
   }
   
   // output: +43 (664) 1234567
   // output: +43 (4321) 1234-567