[Qt-interest] QThread and QNetwork

[BRM]

----- Original Message ----

> From: Matias Hernandez Arellano <msdark at archlinux.cl>
> To: qt-interest at qt.nokia.com
> (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 ...
> 

Setup the signals/slots to provide the communication of data you need - e.g. 
data from the DB and data to the DB - then just do the following in main:


QThread dbCheckThread;

db->moveToThread(&dbCheckThread)
dbCheckThread.start();

Ben

P.S. You do not need the DBCheck* db = new DBCheck() in your example, you could 
just put it on the stack (e.g. DBCheck db - just remember to do &db where you 
need the pointer (e.g. connect()).