QT: manage the reply from a QNetworkReply - c++

Question

I'm new in QT development and I've to make a non-gui application that reads a token from a POST request and then launches some json requests using that token. My problem is what to do when the finished signal is launched. I've tried to pass the reply.readAll() to a QByteArray parameter of the object, but when I do this the value is always empty (""). My code was done based on this.
.h
#ifndef DOWNLOADER_H
#define DOWNLOADER_H
#include <QObject>
#include <QNetworkAccessManager>
class QNetworkReply;
class Downloader : public QObject
{
Q_OBJECT
public:
Downloader(QObject* parent=0);
void test();
bool finished = false;
QByteArray data;
public slots:
void handleReply(QNetworkReply* reply);
protected:
QNetworkAccessManager m_manager;
};
#endif // DOWNLOADER_H
.cpp
#include "downloader.h"
#include <QNetworkRequest>
#include <QNetworkReply>
#include <QUrl>
#include <QVariant>
#include <QDebug>
Downloader::Downloader(QObject *parent) :
QObject(parent)
{
connect(&m_manager, SIGNAL(finished(QNetworkReply*)), SLOT(handleReply(QNetworkReply*)));
}
void Downloader::test() {
QNetworkRequest request;
QUrl url("http://192.168.25.25:8080/path/to/token");
QUrl postData;
postData.addQueryItem("client_id", "foo");
postData.addQueryItem("username", "bar");
postData.addQueryItem("password", "12345");
postData.addQueryItem("grant_type", "password");
request.setUrl(url);
request.setHeader(QNetworkRequest::ContentTypeHeader,"application/x-www-form-urlencoded");
QNetworkReply* rep = m_manager.post(request,postData.encodedQuery());
rep->setProperty("url", QVariant(url));
qDebug() << "Post " << rep << rep->url();
}
void Downloader::handleReply(QNetworkReply *reply) {
qDebug() << "Handle" << reply << reply->url();
qDebug() << "Dynamic property" << reply->property("url").isValid() << reply->property("url");
qDebug() << "ReadAll " << reply->readAll();
finished = true;
data =reply->readAll();
reply->deleteLater();
}
In main, the call is:
Downloader down;
down.test();
while (!down.finished)
{
usleep(3*1000*1100);//3,3s
cout << "no finalizado";
}
What I'm trying to do is to use the reply to fill a parameter and use this parameter from the main, when the finished bool is true. I know it's not correct, but I don't know how to manage the asynchronous nature of the request. What I need it's some guide to understand what I'm doing, since I've been searching in qt page, stackoverflow and others without success. Thanks in advance.
Update: my main function
int main(int argc, char *argv[])
{
QCoreApplication a(argc, argv);
Downloader down;
down.test();
return a.exec();
}

Answer 1

In class Downloader, declare a signal to emit the data to a slot of another QObject derived class. For example, in Downloader::handleReply you call emit dataReady(data). In the main function add below code:
Downloader down;
JsonSender obj;
connect(&down, &Downloader::dataReady, &obj, &JsonSender::dataReady);
down.test();
return a.exec();
In the slot dataReady of class JsonSender you can parse the token and send the request.