How to input currency format on a text field (from right to left) using Swift?

Question

I have a number let’s say 0.00.

• When the user taps 1. We should have 0.01
• When the user taps 2. We should display 0.

Answer 1

After a lot of trial and error with the suggested answers, I found a pretty straight forward solution:

The setup for the textField needs to be called in your view's setup.

In the switch statement, if the user puts in a number between 0 and 9, the number is added to the previous string value. The default case covers the backspace button and removes the last character from the string.

The locale for the numberFormatter is set to current, so it works with different currencies.

func setupTextField() {
        textField.delegate = self
        textField.tintColor = .clear
        textField.keyboardType = .numberPad
}


func textField(_ textField: UITextField, shouldChangeCharactersIn range: NSRange, replacementString string: String) -> Bool {
    setFormattedAmount(string)
    
    return false
}

private func setFormattedAmount(_ string: String) {
    switch string {
    case "0", "1", "2", "3", "4", "5", "6", "7", "8", "9":
        amountString = amountString + string
    default:
        if amountString.count > 0 {
            amountString.removeLast()
        }
    }
    
    let amount = (NSString(string: amountString).doubleValue) / 100
    textField.text = formatAmount(amount)
}

private func formatAmount(_ amount: Double) -> String {
    let formatter = NumberFormatter()
    formatter.numberStyle = .currency
    formatter.locale = .current
    
    if let amount = formatter.string(from: NSNumber(value: amount)) {
        return amount
    }
    
    return ""
}