public function exists( $message = null)
    {
        $this->setRule(__FUNCTION__, function ($val) {
            return null !== $val;
        }, $message);
        return $this;
    }
public function exists( $message = null)
    {
        $this->setRule(__FUNCTION__, function ($val) {
            return null !== $val;
        }, $message);
        return $this;
    }
public function exists ( $ message = null ) { $ this -> setRule ( __FUNCTION__ , function ( $ val ) { return null !== $ val ; } , $ message ) ; return $ this ; }
Field must exist, even if empty

@param null $message
@return $this
Field must exist even if empty