bubasuma\simplechat\db\ConversationQuery::init PHP Method

    public function init()
    {
        parent::init();
        $this->alias('c');
        $this->select(['last_message_id' => new Expression('MAX([[id]])'), 'contact_id' => new Expression('IF([[sender_id]] = :userId, [[receiver_id]], [[sender_id]])')])->andWhere(['or', ['receiver_id' => new Expression(':userId'), 'is_deleted_by_receiver' => false], ['sender_id' => new Expression(':userId'), 'is_deleted_by_sender' => false]])->groupBy(['contact_id']);
    }