     
     
     /**
-     the placeholder string for the current inputField
+     The placeholder string for the current input field
      
      - returns: an Attributed String that is the placeholder of the receiver
      */


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

    
    
    /**
    Delegate method implementation
    
    - parameter textField: Text field
    - 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)
        
