public function getAssignment($roleName, $userId)
    {
        if ($this->isEmptyUserId($userId)) {
            return null;
        }

        $row = (new Query())->from($this->assignmentTable)
            ->where(['user_id' => (string) $userId, 'item_name' => $roleName])
            ->one($this->db);

        if ($row === false) {
            return null;
        }

        return new Assignment([
            'userId' => $row['user_id'],
            'roleName' => $row['item_name'],
            'createdAt' => $row['created_at'],
        ]);
    }
public function getAssignment($roleName, $userId)
    {
        if ($this->isEmptyUserId($userId)) {
            return null;
        }

        $row = (new Query())->from($this->assignmentTable)
            ->where(['user_id' => (string) $userId, 'item_name' => $roleName])
            ->one($this->db);

        if ($row === false) {
            return null;
        }

        return new Assignment([
            'userId' => $row['user_id'],
            'roleName' => $row['item_name'],
            'createdAt' => $row['created_at'],
        ]);
    }
{@inheritdoc}