     
     
     /**
-     subclassed method that is called when textField content was changed
+     Subclassed method that is called when text field content was changed
      
      - parameter textField: the textfield of which the content has changed
      */

    
    
    /**
    delegate method implementation
    
    - parameter textField: textField
    - parameter range:     range
    - parameter string:    string
    
    - returns: boolean to change characters in given range for a textfield
    */
    public func textField(textField: UITextField, shouldChangeCharactersInRange range: NSRange, replacementString string: String) -> Bool {
        
        // only handle delegate calls for own textfield
        guard textField == self.textField else { return false }
        
        // get old and new text
        let oldString = textField.text!
        let newString = (oldString as NSString).stringByReplacingCharactersInRange(range, withString: string)
        


/**
 
 The IssueNumberInputField is an input field configured to detect, validate and present issue numbers for Maestro cards.
 
 */
public class IssueNumberInputField: JudoPayInputField {
