Adding space between textfield character when typing in text filed

Question

I have a textfield with maximum character range 16, After every 4 characters, I want to add minus character or space and then writing The rest of the characters

Answer 1

To do it "on the fly", I connected Editing changed to this IBAction ; needs also to care for backspace

 @IBAction func editingTestField(_ sender: UITextField) {
      if sender.text!.count > 0 && sender.text!.count % 5 == 0 && sender.text!.last! != "-" {
         sender.text!.insert("-", at:sender.text!.index(sender.text!.startIndex, offsetBy: sender.text!.count-1) )
      }
 }

Answer 2

Use shouldChangeCharactersIn like this way.

func textField(_ textField: UITextField, shouldChangeCharactersIn range: NSRange, replacementString string: String) -> Bool {
    if [6, 11, 16].contains(textField.text?.count ?? 0) && string.isEmpty {
        textField.text = String(textField.text!.dropLast())
        return true
    }
    let text = NSString(string: textField.text ?? "").replacingCharacters(in: range, with: string).replacingOccurrences(of: "-", with: "")
    if text.count >= 4 && text.count <= 16 {
        var newString = ""
        for i in stride(from: 0, to: text.count, by: 4) {
            let upperBoundIndex = i + 4
            let lowerBound = String.Index.init(encodedOffset: i)
            let upperBound = String.Index.init(encodedOffset: upperBoundIndex)
            if upperBoundIndex <= text.count  {
                newString += String(text[lowerBound..<upperBound]) + "-"
                if newString.count > 19 {
                   newString = String(newString.dropLast())
                }
            }
            else if i <= text.count {
                newString += String(text[lowerBound...])
            }
        }
        textField.text = newString
        return false
    }
    if text.count > 16 {
        return false
    }
    return true
}

Note: I have used - (Hyphen) you can simply replace it with Space if you want Space instead of - (Hyphen).

Edit: Code is edited to latest swift 4.*, for older swift version please check edit history.

Answer 3

We may start by implementing a Swift 3 version of the chunk(n:) method (for Collection's) of oisdk:s SwiftSequence:

/* Swift 3 version of Github use oisdk:s SwiftSequence's 'chunk' method:
   https://github.com/oisdk/SwiftSequence/blob/master/Sources/ChunkWindowSplit.swift */
extension Collection {
    public func chunk(n: IndexDistance) -> [SubSequence] {
        var res: [SubSequence] = []
        var i = startIndex
        var j: Index
        while i != endIndex {
            j = index(i, offsetBy: n, limitedBy: endIndex) ?? endIndex
            res.append(self[i..<j])
            i = j
        }
        return res
    }
}

In which case implementing your custom formatting is a simple case of creating 4-character chunks and joining these by "-":

func customStringFormatting(of str: String) -> String {
    return str.characters.chunk(n: 4)
        .map{ String($0) }.joined(separator: "-")
}

Example usage:

print(customStringFormatting(of: "5022222222222222")) // 5022-2222-2222-2222
print(customStringFormatting(of: "50222222222222"))   // 5022-2222-2222-22
print(customStringFormatting(of: "5022222"))          // 5022-222

---

If applying to be used in the textField(_:shouldChangeCharactersIn:replacementString:) method of UITextFieldDelegate, we might want to filter out existing separators in the customStringFormatting(of:) method method, as well as implementing it as a String extension:

extension String {
    func chunkFormatted(withChunkSize chunkSize: Int = 4, 
        withSeparator separator: Character = "-") -> String {
        return characters.filter { $0 != separator }.chunk(n: chunkSize)
            .map{ String($0) }.joined(separator: String(separator))
    }
}

And implement the controlled updating of the textfield e.g. as follows:

let maxNumberOfCharacters = 16

func textField(_ textField: UITextField, shouldChangeCharactersIn range: NSRange, replacementString string: String) -> Bool {
    // only allow numerical characters
    guard string.characters.flatMap({ Int(String($0)) }).count ==
        string.characters.count else { return false }

    let text = textField.text ?? ""

    if string.characters.count == 0 {
        textField.text = String(text.characters.dropLast()).chunkFormatted()
    }
    else {
        let newText = String((text + string).characters
            .filter({ $0 != "-" }).prefix(maxNumberOfCharacters))
        textField.text = newText.chunkFormatted()
    }
    return false
}

The last part above will truncate possible pasted strings from the user (given that it's all numeric), e.g.

// current 
1234-1234-123

// user paste:
777777777
  /* ^^^^ will not be included due to truncation */  

// will result in
1234-1234-1237-7777