* @return $fieldValue Field value from the user
* @throws NullPointerException If the result instance is null
*/
- function getField ($fieldName);
+ function getField (string $fieldName);
/**
* Checks if given field is set
* @return $isSet Whether the given field name is set
* @throws NullPointerException If the result instance is null
*/
- function isFieldSet ($fieldName);
+ function isFieldSet (string $fieldName);
/**
* Setter for call-back instance