QT SQL notification with payload - c++

Question

I'm currently working on applciation that will add to table view new row, that was inserted into db's table. I started with basic class to handle notifies and setted up triggers:
CREATE OR REPLACE FUNCTION notify_tableIWantToObserve_update()
RETURNS trigger AS $$
DECLARE
BEGIN
PERFORM pg_notify(
CAST('tableIWantToObserve_update' AS text),
(NEW.tableIWantToObserve_id)::text);
return new;
END;
$$ LANGUAGE plpgsql;
CREATE TRIGGER tRIGGER_notify_tableIWantToObserve_update
AFTER UPDATE
ON tableIWantToObserve
FOR EACH ROW
EXECUTE PROCEDURE notify_tableIWantToObserve_update();
So it will jsut send notfy with id of updated row in payload. That is what i want - becous reloading whole table just won't do the trick later.
I checked documentaton of QSqlDriver
http://doc.qt.io/qt-5/qsqldriver.html#notification-1
With it, I created my "handler":
// That's its constructor
MyDB = new QSqlDatabase(QSqlDatabase::addDatabase("QPSQL", "Main"));
//Removed my data from here (just fro sake of this post)
MyDB->setHostName("-");
MyDB->setPort(0);
MyDB->setDatabaseName("-");
MyDB->setUserName("-");
MyDB->setPassword("-");
MyDB->open();
if( MyDB->isOpen() )
{
qDebug()<<"Connected to DB!";
QObject::connect(
MyDB->driver(),
SIGNAL(notification(const QString&, QSqlDriver::NotificationSource, const QVariant)),
this,
SLOT(slot_DBNotification_Recieved_NotifiAndPayload((const QString&, const QVariant)));
);
}
else
qDebug()<<"NOT connected to DB!";
But it jsut wont work. Only with driver's signal useing single QString it will connect it - version i needed (with additional info) wont connect.
I updated my QT to 5.7, but still even in QTCreater, it just shows me that driver's signal is only with single string.
Is there any fix for that? I realy need to use that signal to retrieve that updated row id.
EDIT 1:
that slot of my handler:
void NotifiHandlerr::slot_DBNotification_Recieved_NotifiAndPayload(const QString& MSG, const QVariant &payload)
{
qDebug() << "I WAS NOTIFIED ABOUT : " + MSG+" WITH DATA : "+payload.toString();
}
EDIT 2:
I tried to add QSqlDriver::NotificationSource as argument in my slot, but i couldn't - it still repeated error in .h that NotificationSource wasn't declared.
EDIT 3:
I'm adding here most of the code (handler class)
// WHOLE .h
#include <QDebug>
#include <QObject>
#include <QString>
#include <QSqlDatabase>
#include <QSqlDriver>
#include <QVariant>
#include <QSqlDriverPlugin>
#include <qsqldriver.h>
class Handler : public QObject
{
Q_OBJECT
public slots:
void slot_DBNotification_Recieved_NotifiAndPayload
(const QString& name, QSqlDriver::NotificationSource source, const QVariant& payload);
public:
explicit Handler();
~Handler();
private:
QSqlDatabase MyDB;
};
//WHOLE .cpp
#include "Handler.h"
Handler::Handler()
{
MyDB = new QSqlDatabase(QSqlDatabase::addDatabase("QPSQL", "Main"));
MyDB->setHostName("-");
MyDB->setPort(0);
MyDB->setDatabaseName("-");
MyDB->setUserName("-");
MyDB->setPassword("-");
MyDB->open();
if( MyDB->isOpen() )
{
qDebug()<<"Connected to DB!";
MyDB->driver()->subscribeToNotification("tableIWantToObserve_update");
QObject::connect(
MyDB->driver(),
SIGNAL(notification(const QString&, QSqlDriver::NotificationSource, const QVariant)),
this,
SLOT(slot_DBNotification_Recieved_NotifiAndPayload((const QString&, const QVariant)));
);
}
else
qDebug()<<"NOT connected to DB!";
}
Handler::~Handler()
{
MyDB->driver()->unsubscribeFromNotification("tableIWantToObserve_update");
MyDB->cloe();
}
void NotificationMaster::slot_DBNotification_Recieved_NotifiAndPayload
(const QString &name, QSqlDriver::NotificationSource source, const QVariant &payload)
{
qDebug() << "I WAS NOTIFIED ABOUT : " + name+" WITH DATA : "+payload.toString();
}
And just to eliminate this idea - I added
QT += sql
in my .pro file

Answer 1

Your slot has a wrong signature, Here is how you should define it.
In your header file:
//in order to be able to use the enum QSqlDriver::NotificationSource
#include <QSqlDriver>
...
...
class Handler : public QObject{
Q_OBJECT
public:
explicit Handler(QObject *parent = 0);
~Handler();
...
...
...
public slots:
void SqlNotification(const QString& name, QSqlDriver::NotificationSource source,
const QVariant& payload);
...
...
};
and in the constructor, when you are connecting the slot, you should subscribe to the notification first:
QSqlDatabase::database().driver()->subscribeToNotification("notification_name");
connect(QSqlDatabase::database().driver(),
SIGNAL(notification(QString,QSqlDriver::NotificationSource,QVariant)), this,
SLOT(SqlNotification(QString,QSqlDriver::NotificationSource,QVariant)));
You may need to unsubscribe in the destructor(since you don't want to receive the notification any more):
QSqlDatabase::database().driver()->unsubscribeFromNotification("notification_name");
and your slot implementation:
void Handler::SqlNotification(const QString &name, QSqlDriver::NotificationSource source, const QVariant &payload){
switch(source){
case QSqlDriver::UnknownSource:
qDebug() << "unkown source, name: " << name << "payload:" << payload.toString();
break;
case QSqlDriver::SelfSource:
qDebug() << "self source, name: " << name << "payload:" << payload.toString();
break;
case QSqlDriver::OtherSource:
qDebug() << "other source, name: " << name << "payload:" << payload.toString();
break;
}
}

Answer 2

Code posted by me and in anserw were more-or-less correct, but what need to be done is to recreate whoel project in newer version of qt creator so it will resolve issiues with missing functions and namespaces itself. Just create new project and paste all files there.