UITextField extension

UITextFieldExtension.swift

import Foundation

extension UITextField {
  func containsOnlyNumbers(string: String, maximumDecimalPlaces: NSInteger, maximumValue: NSInteger) -> Bool {
    // Check that textfield only contains allowed number of decimal places (this can also be done in regex, but avoiding so that is easier to understand and debug
    if string.characters.contains(".") {
      if string.componentsSeparatedByString(".").count > 2 {
        return false
      } else {
        let newStringSplitAtDecimal = string.componentsSeparatedByString(".")
        if newStringSplitAtDecimal.count > 1 {
          let decimalPlaces = newStringSplitAtDecimal.last
          if decimalPlaces?.characters.count > maximumDecimalPlaces {
            return false
          }
        }
      }
    }
    // Check that textfield only contains numbers and decimal (.)
    let regularExpression = maximumDecimalPlaces > 0 ? "^[0-9.]*$" : "^[0-9]*$"
    do {
      let regex = try NSRegularExpression(pattern: regularExpression, options: .CaseInsensitive)
      let numberOfMatches = regex.numberOfMatchesInString(string, options: .Anchored, range: NSMakeRange(0, string.characters.count))
      if numberOfMatches == 0 {
        return false
      }
    } catch {
      return false
    }
    let stringInt = (string as NSString).integerValue
    if stringInt > maximumValue {
      return false
    }
    return true
  }
}