Slot doesn't get triggered on HTTP reply

rackover

Hi,
I'm trying to fetch JSON data from a web page using QNetworkRequest, but the slot never gets triggered despite the URL being valid and working. I've tried with any URL and it does not work.
Heres my code :

///header file
#ifndef DOWNLOADER_H
#define DOWNLOADER_H

#include <QObject>
#include <QJsonObject>
#include <QNetworkReply>

#include <mutex>
#include <condition_variable>

namespace Pico{
    namespace Downloader{

        class Funcs : public QObject
        {
            Q_OBJECT
            public:
                explicit Funcs(QObject *parent = 0);
                void DownloadFiles(std::map<std::string, int> &downloadsMap);
                void PopulateDownloadsMap(QJsonObject game, std::map<std::string, int> downloadsMap);

                struct currentDownload{
                    std::condition_variable    finished;
                    int                     state;
                    std::string              details;
                    QString                   data;
                    std::mutex               lock;
                };

            signals:

            public slots:
                void onAPIResponse(QNetworkReply*);

            private:

        };
    }
}

#endif // DOWNLOADER_H

               //function to start the download

               std::string modApiPage = "https://api.faforever.com/data/mod?page[size]=1&filter=versions.uid=="+uid+"&include=versions&fields[modVersion]=downloadUrl";

                /// Fetch download address from API using mod UID
                const QUrl url = QUrl(QString::fromStdString(modApiPage));
                const QNetworkRequest request(url);
                QNetworkAccessManager networkManager;
                connect(&networkManager, SIGNAL(finished(QNetworkReply*)), this, SLOT(onAPIResponse(QNetworkReply*))) ;

 void Funcs::onAPIResponse(QNetworkReply* reply)
        {
            logging.Write("ON_VAULT_RESPONSE => Received data from the API");
            ...further operations...
        }

Am I doing something wrong ? I"ve tried following multiple tutorials but I can"t get this to work.

Paul Colby

Hi @rackover,

Where you have:

QNetworkAccessManager networkManager;
connect(&networkManager, SIGNAL(finished(QNetworkReply*)), this, SLOT(onAPIResponse(QNetworkReply*))) ;

The signal is disconnected and networkManager destroyed immediately after the function ends - ie when accessManager goes out of scope. Possibly this is just because you simplified the code to show us the sample, but you should either be allocating networkManager outside this function, or allocating it on a heap.

eg:

QNetworkAccessManager * networkManager = new QNetworkAccessManager(this);
connect(networkManager, SIGNAL(finished(QNetworkReply*)), this, SLOT(onAPIResponse(QNetworkReply*))) ;

Cheers.

raven-worx

@rackover said in Slot doesn't get triggered on HTTP reply:

QNetworkAccessManager networkManager;

you create the QNetworkAccessManager isnatnce on the stack, which means it gets automatically deleted on the end of the block it is created in.
When this is not intentional, this is your issue. Create it on the heap (pointer) and set a parent object on it and it should work.

Edit: too slow :)

rackover

@Paul-Colby said in Slot doesn't get triggered on HTTP reply:

QNetworkAccessManager * networkManager = new QNetworkAccessManager(this);
connect(networkManager, SIGNAL(finished(QNetworkReply*)), this, SLOT(onAPIResponse(QNetworkReply*))) ;

Hi,
Thanks from the help from you both. I've tried correcting the code, but the signal still doesn't get triggered.

               std::string modApiPage = "https://api.faforever.com/data/mod?page[size]=1&filter=versions.uid=="+uid+"&include=versions&fields[modVersion]=downloadUrl";

                /// Fetch download address from API using mod UID
                const QUrl url = QUrl(QString::fromStdString(modApiPage));
                const QNetworkRequest request(url);
                QNetworkAccessManager * networkManager = new QNetworkAccessManager(this);
                connect(networkManager, SIGNAL(finished(QNetworkReply*)), this, SLOT(onAPIResponse(QNetworkReply*))) ;

jsulm

@rackover said in Slot doesn't get triggered on HTTP reply:

QNetworkAccessManager * networkManager = new QNetworkAccessManager(this);

Is this the one QNetworkAccessManager you're using for request?
Also check whether connect() actually succeeded.

rackover

Yes, I believe this is the networkmanager i'm using. How can I check that ?
Connect doesn't return a bool nor a int, I'm not sure of how I should check it's working or not. At least it's not returning any errors.

jsulm

@rackover If the old style connect fails you will see a warning at runtime (in application output tab in QtCreator).

rackover

Then I guess it is not failing. There is no warning neither at runtime nor in IDE. Is there any other possibility I can explore ?

SGaist

Hi,

You should also connect the error related signal.

rackover

Hi,

Thank you for your help, could you please expand a little bit ? I'm not sure of what you mean by connecting the "error related" signal. Isn't it what I'm actually doing ?

SGaist

You only connect the finished signal. There's also sslErrors.

Do you also have OpenSSL properly installed on your system ?

rackover

I don't, but since it is not working with a classic HTTP address neither, I didn't look into SSL-stuff yet.

SGaist

Then connect the error signal of the QNetworkReply you get back when doing the request.

rackover

I get no Network reply back when I'm doing the request. The whole point of this topic is that, the slot getting never triggered, the function that handles the QNetworkReply doesn't fire and therefore, I have no NetworkReply to work with nor to debug.

SGaist

Might be a silly question but since I don't see it in any of it your code snippet, are you calling QNetworkAccessManager::get at some point ?

rackover

Ah, yeah, well it surely wasn't going to work without a get. How did I miss that.
Thank you.

Slot doesn't get triggered on HTTP reply

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