Limit Text Field to one decimal point input, numbers only, and two characters after the decimal place - Swift 3

Question

I am struggling to do this with Swift 3. I have a text field that I would like to limit to only numbers and one decimal point and two characters after the decimal place. I would also like to have it work in regions where a decimal point is not used when entering non-integers. Thank you for any suggestions!

Answer 1

You need to assign delegate to your textfield and in the shouldChangeCharactersIn delegate method do your validations:

1. Add extension with validation methods for the string:

   extension String{
   
       private static let decimalFormatter:NumberFormatter = {
           let formatter = NumberFormatter()
           formatter.allowsFloats = true
           return formatter
       }()
   
       private var decimalSeparator:String{
           return String.decimalFormatter.decimalSeparator ?? "."
       }
   
       func isValidDecimal(maximumFractionDigits:Int)->Bool{
   
           // Depends on you if you consider empty string as valid number
           guard self.isEmpty == false else {
               return true
           }
   
           // Check if valid decimal
           if let _ = String.decimalFormatter.number(from: self){
   
               // Get fraction digits part using separator
               let numberComponents = self.components(separatedBy: decimalSeparator)
               let fractionDigits = numberComponents.count == 2 ? numberComponents.last ?? "" : ""
               return fractionDigits.characters.count <= maximumFractionDigits
           }
   
           return false
       }
   
   }
   

2. In your delegate method:

   func textField(_ textField: UITextField, shouldChangeCharactersIn range: NSRange, replacementString string: String) -> Bool {
   
       // Get text
       let currentText = textField.text ?? ""
       let replacementText = (currentText as NSString).replacingCharacters(in: range, with: string)
   
       // Validate
       return replacementText.isValidDecimal(maximumFractionDigits: 2)
   
   }