I'm trying to format numbers in a UITextField consists of math equation String: "number + number".
At the moment I can type just a single number, then convert it to Double -> format with NSNumberFormatter -> convert back to String -> assign to textField.text: https://i.stack.imgur.com/4qQza.gif
The code:
func textField(_ textField: UITextField, shouldChangeCharactersIn range: NSRange, replacementString string: String) -> Bool {
let formatter = NumberFormatter()
formatter.numberStyle = .decimal
formatter.maximumFractionDigits = 2
formatter.locale = .current
formatter.roundingMode = .down
let numberString = textField.text ?? ""
guard let range = Range(range, in: numberString) else { return false }
let updatedString = numberString.replacingCharacters(in: range, with: string)
let correctDecimalString = updatedString.replacingOccurrences(of: formatter.decimalSeparator, with: ".")
let completeString = correctDecimalString.replacingOccurrences(of: formatter.groupingSeparator, with: "")
guard let value = Double(completeString) else { return false }
let formattedNumber = formatter.string(for: value)
textField.text = formattedNumber
return string == formatter.decimalSeparator
}
Now I want to add a calculation functionality and display a simple math equation in a textField as "number + number", but each number should be formatted as shown on above screenshot. Example (but without formatting): https://i.stack.imgur.com/W7Jet.gif
I can't properly implement that. The logic for me was: track the String each time new char inserts -> if it has math sign extract numbers -> convert them to Double -> format with NSNumberFormatter -> convert back to String -> construct a new String "number + number".
The code I tried:
if let firstString = completeString.split(separator: "+").first, let secondString = completeString.split(separator: "+").last {
guard let firstValue = Double(firstString) else { return false }
guard let secondValue = Double(secondString) else { return false }
let firstFormattedNumber = formatter.string(for: firstValue)
let secondFormattedNumber = formatter.string(for: secondValue)
textField.text = "\(firstFormattedNumber ?? "") + \(secondFormattedNumber ?? "")"
// another try
if completeString.contains("+") {
let stringArray = completeString.components(separatedBy: "+")
for character in stringArray {
print(character)
guard let value = Double(character) else { return false }
guard let formattedNumber = formatter.string(for: value) else { return false }
textField.text = "\(formattedNumber) + "
}
}
But it's not working properly. I tried to search but didn't find any similar questions.
How can I format the numbers from such a string?
Here is how I solved my problem:
func textField(_ textField: UITextField, shouldChangeCharactersIn range: NSRange, replacementString string: String) -> Bool {
let formatter = NumberFormatter()
formatter.numberStyle = .decimal
formatter.maximumFractionDigits = 2
formatter.locale = .current
formatter.roundingMode = .down
//set of possible math operations
let symbolsSet = Set(["+","-","x","/"])
let numberString = textField.text ?? ""
guard let range = Range(range, in: numberString) else { return false }
let updatedString = numberString.replacingCharacters(in: range, with: string)
let correctDecimalString = updatedString.replacingOccurrences(of: formatter.decimalSeparator, with: ".")
let completeString = correctDecimalString.replacingOccurrences(of: formatter.groupingSeparator, with: "")
//receive math symbol user typed
let symbol = symbolsSet.filter(completeString.contains).first ?? ""
//receive number of symbols in a String. If user wants to type more than one math symbol - do not insert
let amountOfSymbols = completeString.filter({String($0) == symbol}).count
if amountOfSymbols > 1 { return false }
//receive numbers typed by user
let numbersArray = completeString.components(separatedBy: symbol)
//check for each number - if user wants to type more than one decimal sign - do not insert
for number in numbersArray {
let amountOfDecimalSigns = number.filter({$0 == "."}).count
if amountOfDecimalSigns > 1 { return false }
}
guard let firstNumber = Double(String(numbersArray.first ?? "0")) else { return true }
guard let secondNumber = Double(String(numbersArray.last ?? "0")) else { return true }
let firstFormattedNumber = formatter.string(for: firstNumber) ?? ""
let secondFormattedNumber = formatter.string(for: secondNumber) ?? ""
// if user typed math symbol - show 2 numbers and math symbol, if not - show just first typed number
textField.text = completeString.contains(symbol) ? "\(firstFormattedNumber)\(symbol)\(secondFormattedNumber)" : "\(firstFormattedNumber)"
return string == formatter.decimalSeparator
}