[Qt-interest] QThread and QNetwork

[Matias Hernandez Arellano]

(sorry for my english)

Hi, i'm trying do make an application to query a couchdb database using HTTP request to the _change API of the database.

To do this i create a class (DBCheck) that make a request to the _change API using the continuos feed, this is a HTTP connection that live forever and make possible to notify the client when a change occur in DB (real time, like Push notification).

Then i create another class (just for test) no show a notification (in console) of the change.

I connect this two classes using Signals and Slots.

Now i need to make this work with a GUI, the idea is show in a part of the GUI a "table" that auto--update any change in DB (when DB notify for changes)..

To do this i thought i need to use Threads, so for testing purpose i create a console application and try to run this, but i can't make that the Http class (DBCheck) run inside a thread an notify every change to the main thread (or other object using signals) .. i get an error about the diferents parents of the object..

So this is the code (without thread)
 #ifndef DBCHECK_H
#define DBCHECK_H
#include <QNetworkAccessManager>
#include <QUrl>
#include <QObject>
#include <QByteArray>
#include <qjson/parser.h>
#include <QVariantMap>
#include <QDebug>
class QNetworkReply;
class DBCheck: public QObject
{
    Q_OBJECT
public:
    DBCheck();
    void startRequest(QUrl);
signals:
    void change();
private slots:
    void httpFinished();
    void httpReadyRead();
private:
    QUrl url;
    QNetworkAccessManager qnam;
    QNetworkReply *reply;
};

 DBCheck::DBCheck()
{
}
void DBCheck::startRequest(QUrl url){
    reply = qnam.get(QNetworkRequest(url));
    connect(reply, SIGNAL(finished()),this, SLOT(httpFinished()));
    connect(reply, SIGNAL(readyRead()),this, SLOT(httpReadyRead()));
    return;
}
void DBCheck::httpFinished(){
    qDebug()<<"Finished";
    return;
}
void DBCheck::httpReadyRead(){
    this->result = this->reply->readAll();
    emit change();
}


//the other class
 #ifndef NOTIF_H
#define NOTIF_H
#include <QObject>
#include <QDebug>
class Notif:public QObject{
    Q_OBJECT
public:
    Notif(){
    }
    ~Notif(){
    }
public slots:
    void notificar(){
        qDebug()<<"Cambio!";
    }
};
#endif // NOTIF_H

and the main.cpp
 #include <QCoreApplication>
#include "dbcheck.h"
#include "notif.h"
#include <QDebug>
 int main(int argc, char *argv[]){
     QCoreApplication app(argc, argv);
     DBCheck *db = new DBCheck();
     Notif *t = new Notif();
     QObject::connect(db,SIGNAL(change()),t,SLOT(notificar()));
     db->startRequest(QUrl("http://127.0.0.1:5984/test/_changes?feed=continuous&since=39"));
     return app.exec();
 }

How can i run the DBCheck object in a thread???

any guideline or idea would very appreciate ...

Thanks in advance.

Matías Hernandez Arellano
Ingeniero de Software/Proyectos en VisionLabs S.A
CDA Archlinux-CL
www.msdark.archlinux.cl