Unable to fetch data from the ResultSet object array in zf3

I am using zend framework3 and using the Mysql driver for the database. I am using the below code to get the data:

        $con = $this->adapter;
        $select = $this->sql->select();
        $select->from('nav_menu');
        $selectString = $this->sql->getSqlStringForSqlObject($select);
        $results = $con->query($selectString, $con::QUERY_MODE_EXECUTE);
        $resultSet = new ResultSet();
        $resultSet->initialize($results); 

when i var_dump this data i am getting the result as below:

   Zend\Db\ResultSet\ResultSet Object
   (
    [allowedReturnTypes:protected] => Array
    (
        [0] => arrayobject
        [1] => array
    )
    [arrayObjectPrototype:protected] => ArrayObject Object
    (
        [storage:ArrayObject:private] => Array
            (
            )
        )

[returnType:protected] => arrayobject
[buffer:protected] => 
[count:protected] => 
[dataSource:protected] => Zend\Db\ResultSet\ResultSet Object
    (
        [allowedReturnTypes:protected] => Array
            (
                [0] => arrayobject
                [1] => array
            )

        [arrayObjectPrototype:protected] => ArrayObject Object
            (
                [storage:ArrayObject:private] => Array
                    (
                    )

            )

        [returnType:protected] => arrayobject
        [buffer:protected] => -1
        [count:protected] => 
        [dataSource:protected] => Zend\Db\Adapter\Driver\Mysqli\Result Object
            (
                [resource:protected] => mysqli_result Object
                    (
                        [current_field] => 0
                        [field_count] => 8
                        [lengths] => 
                        [num_rows] => 15
                        [type] => 0
                    )

                [isBuffered:protected] => 1
                [position:protected] => 0
                [numberOfRows:protected] => -1
                [currentComplete:protected] => 
                [nextComplete:protected] => 
                [currentData:protected] => 
                [statementBindValues:protected] => Array
                    (
                        [keys] => 
                        [values] => Array
                            (
                            )

                    )

                [generatedValue:protected] => 0
            )

        [fieldCount:protected] => 8
        [position:protected] => 0
    )

[fieldCount:protected] => 
[position:protected] => 0
)

I am getting an error When i am iterating this to get the value as below:

       foreach ($resultSet as $key => $value) {
            $array[$i]['id'] = $value->id;
            $array[$i]['name'] = $value->name;
            $array[$i]['label'] = $value->label;
            $array[$i]['route'] = $value->route;
            $array[$i]['parent_id'] = $value->parent_id;
            $i++;
        }

I don't where i am wrong. While there are num_rows is 15. This is working in ZF2 fine. Any help from any one is appreciated.

I tried a lot and find that if replace the code

    $selectString = $this->sql->getSqlStringForSqlObject($select);
    $results = $con->query($selectString, $con::QUERY_MODE_EXECUTE);

with the

    $statement = $this->sql->prepareStatementForSqlObject($select);
    $results = $statement->execute(); 

then i get the result.But my question why i am not getting the result through

    $selectString = $this->sql->getSqlStringForSqlObject($select);
    $results = $con->query($selectString, $con::QUERY_MODE_EXECUTE);