How do you dynamically format a number to have commas in a UITextField entry?

Question

I want to have commas dynamically added to my numeric UITextField entry while the user is typing.

For example: 123,456 and 12,345,678

Answer 1

Here is a solution in swift 4.

 @objc func textFieldValDidChange(_ textField: UITextField) {
    let formatter = NumberFormatter()
    formatter.numberStyle = NumberFormatter.Style.decimal
    if textField.text!.count >= 1 {
       let number = Double(bottomView.balanceTxtField.text!.replacingOccurrences(of: ",", with: ""))
        let result = formatter.string(from: NSNumber(value: number!))
        textField.text = result!
    }
}

Don't forget to add editingChanged action as below:

textField.addTarget(self, action:#selector(ViewController.textFieldValDidChange), for: .editingChanged)

Answer 2

Here is a version in Swift 4. I used it for integers, I didn't check with decimal numbers.

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

     // Uses the number format corresponding to your Locale
     let formatter = NumberFormatter()
     formatter.numberStyle = .decimal
     formatter.locale = Locale.current
     formatter.maximumFractionDigits = 0


    // Uses the grouping separator corresponding to your Locale
    // e.g. "," in the US, a space in France, and so on
    if let groupingSeparator = formatter.groupingSeparator {

        if string == groupingSeparator {
            return true
        }


        if let textWithoutGroupingSeparator = textField.text?.replacingOccurrences(of: groupingSeparator, with: "") {
            var totalTextWithoutGroupingSeparators = textWithoutGroupingSeparator + string
            if string.isEmpty { // pressed Backspace key
                totalTextWithoutGroupingSeparators.removeLast()
            }
            if let numberWithoutGroupingSeparator = formatter.number(from: totalTextWithoutGroupingSeparators),
                let formattedText = formatter.string(from: numberWithoutGroupingSeparator) {

                textField.text = formattedText
                return false
            }
        }
    }
    return true
}

The big advantage of this method is that it uses the grouping separator defined in your current locale (region), because not everybody uses the comma as a grouping separator.

Works with 0, backspace, but, again, I didn't test it with decimals. You are free to enhance this code if you worked it out with decimals.

Examples:

• Enter : "2" -> "2"
• Enter : "3" -> "23"
• Enter : "6" -> "236"
• Enter : "7" -> "2,367"
• Enter : "0" 3 times -> "2,367,000"
• Backspace -> "236,700"

Starting 0 works too:

• Enter : "0" -> "0"
• Enter : "2" -> "2"

Answer 3

I have another one. Fix some bugs with local configuration and zero after decimal point

func textField(_ textField: UITextField, shouldChangeCharactersIn range: NSRange, replacementString string: String) -> Bool {
    
    let point = Locale.current.decimalSeparator!
    let decSep = Locale.current.groupingSeparator!
    
    
    let text = textField.text!
    let textRange = Range(range, in: text)!
    
    var fractionLength = 0
    var isRangeUpperPoint = false
    
    if let startPoint = text.lastIndex(of: point.first!) {
        let end = text.endIndex
        let str = String(text[startPoint..<end])
        fractionLength = str.count
        isRangeUpperPoint = textRange.lowerBound >= startPoint
    }
    
    if  fractionLength == 3 && string != "" && isRangeUpperPoint {
        return false
    }
    
    let r = (textField.text! as NSString).range(of: point).location < range.location
    if (string == "0" || string == "") && r {
        return true
    }
    
    // First check whether the replacement string's numeric...
    let cs = NSCharacterSet(charactersIn: "0123456789\(point)").inverted
    let filtered = string.components(separatedBy: cs)
    let component = filtered.joined(separator: "")
    let isNumeric = string == component
    
    
    if isNumeric {
        let formatter = NumberFormatter()
        formatter.numberStyle = .decimal
        formatter.maximumFractionDigits = 2
        // Combine the new text with the old; then remove any
        // commas from the textField before formatting
        
        
        let newString = text.replacingCharacters(in: textRange,  with: string)
        
        
        let numberWithOutCommas = newString.replacingOccurrences(of: decSep, with: "")
        let number = formatter.number(from: numberWithOutCommas)
        if number != nil {
            var formattedString = formatter.string(from: number!)
            // If the last entry was a decimal or a zero after a decimal,
            // re-add it here because the formatter will naturally remove
            // it.
            if string == point && range.location == textField.text?.count {
                formattedString = formattedString?.appending(point)
            }
            textField.text = formattedString
        } else {
            textField.text = nil
        }
    }
    
    
    
   return false
    
}