Formatting a UITextField for credit card input like (xxxx xxxx xxxx xxxx)

Question

I want to format a UITextField for entering a credit card number into such that it only allows digits to be entered and automatically inserts spaces so that the

Answer 1

swift 5

Hi, here is the swift 5 version of Mark Amery's accepted answer that worked for me

Add these variables in your class.

@IBOutlet weak var cardNumberTextField: UITextField!
private var previousTextFieldContent: String?
private var previousSelection: UITextRange?

And also ensure that your text field calls reformatAsCardNumber: from viewDidLoad()

cardNumberTextField.addTarget(self, action: #selector(reformatAsCardNumber), for: .editingChanged)

Add this in your UITextFieldDelegate

func textField(_ textField: UITextField, shouldChangeCharactersIn range: NSRange, replacementString string: String) -> Bool {
   
    if textField == cardNumberTextField {
        previousTextFieldContent = textField.text;
        previousSelection = textField.selectedTextRange;
    }
    
    return true
}

Lastly include the following methods in your viewController:

@objc func reformatAsCardNumber(textField: UITextField) {
    var targetCursorPosition = 0
    if let startPosition = textField.selectedTextRange?.start {
        targetCursorPosition = textField.offset(from: textField.beginningOfDocument, to: startPosition)
    }
    
    var cardNumberWithoutSpaces = ""
    if let text = textField.text {
        cardNumberWithoutSpaces = self.removeNonDigits(string: text, andPreserveCursorPosition: &targetCursorPosition)
    }
    
    if cardNumberWithoutSpaces.count > 19 {
        textField.text = previousTextFieldContent
        textField.selectedTextRange = previousSelection
        return
    }
    
    let cardNumberWithSpaces = self.insertSpacesEveryFourDigitsIntoString(string: cardNumberWithoutSpaces, andPreserveCursorPosition: &targetCursorPosition)
    textField.text = cardNumberWithSpaces
    
    if let targetPosition = textField.position(from: textField.beginningOfDocument, offset: targetCursorPosition) {
        textField.selectedTextRange = textField.textRange(from: targetPosition, to: targetPosition)
    }
}

func removeNonDigits(string: String, andPreserveCursorPosition cursorPosition: inout Int) -> String {
    var digitsOnlyString = ""
    let originalCursorPosition = cursorPosition
    
    for i in Swift.stride(from: 0, to: string.count, by: 1) {
        let characterToAdd = string[string.index(string.startIndex, offsetBy: i)]
        if characterToAdd >= "0" && characterToAdd <= "9" {
            digitsOnlyString.append(characterToAdd)
        }
        else if i < originalCursorPosition {
            cursorPosition -= 1
        }
    }
    
    return digitsOnlyString
}

func insertSpacesEveryFourDigitsIntoString(string: String, andPreserveCursorPosition cursorPosition: inout Int) -> String {
    var stringWithAddedSpaces = ""
    let cursorPositionInSpacelessString = cursorPosition
    
    for i in Swift.stride(from: 0, to: string.count, by: 1) {
        if i > 0 && (i % 4) == 0 {
            stringWithAddedSpaces.append(contentsOf: " ")
            if i < cursorPositionInSpacelessString {
                cursorPosition += 1
            }
        }
        let characterToAdd = string[string.index(string.startIndex, offsetBy: i)]
        stringWithAddedSpaces.append(characterToAdd)
    }
    
    return stringWithAddedSpaces
}