Selector name found in current argument registers: release

function signature specialization <Arg[0] = Exploded, Arg[1] = Owned To Guaranteed and Exploded> of SpecificTextField.shouldChangeCharactersInRange (__C._NSRange, replacementString : Swift.String) -> Swift.Bool (SpecificTextField.swift:0)
SpecificTextField.shouldChangeCharactersInRange (__C._NSRange, replacementString : Swift.String) -> Swift.Bool (SpecificTextField.swift:91)
function signature specialization <Arg[0] = Dead and Owned To Guaranteed, Arg[1] = Exploded, Arg[2] = Owned To Guaranteed and Exploded> of MyController.textField (__ObjC.UITextField, shouldChangeCharactersInRange : __C._NSRange, replacementString : Swift.String) -> Swift.Bool (MyController.swift:645)
@objc MyController.textField (__ObjC.UITextField, shouldChangeCharactersInRange : __C._NSRange, replacementString : Swift.String) -> Swift.Bool (MyController.swift:0)
...

func textField(textField: UITextField, shouldChangeCharactersInRange range: NSRange, replacementString string: String) -> Bool
{
  if isOptionalObjectNil(string) {
    return false
  }
  return specificTextField?.shouldChangeCharactersInRange(range, replacementString: string) ?? true
}

class SpecificTextField: UITextField
{
  func shouldChangeCharactersInRange(range: NSRange, replacementString string: String) -> Bool {
    ...
  }
}

public func isOptionalObjectNil(testable: AnyObject?) -> Bool
{
  return testable == nil
}