qnetwork reply not emitted finished

fadu

good day for all
i have this code when i run it in console application it's 100% working but when but same code in gui app qnetwork reply didn't emit finished signal!

#include <QCoreApplication>
#include <QJsonObject>
#include <QUrlQuery>
#include <QtNetwork/QNetworkAccessManager>
#include <QtNetwork/QNetworkReply>
#include<QJsonDocument>
#include <QHostAddress>
#include <QHostInfo>
int main(int argc, char *argv[])
{
    QCoreApplication a(argc, argv);
    QNetworkAccessManager networkManager;
    QUrl url("https://api.ipify.org");
    //the query used to add the parameter "format=json" to the request
    QUrlQuery query;
    query.addQueryItem("format", "json");
    //set the query on the url
    url.setQuery(query);
    //make a *get* request using the above url
    QNetworkReply* reply = networkManager.get(QNetworkRequest(url));

    QObject::connect(reply, &QNetworkReply::finished,
                     [=](){
        if(reply->error() != QNetworkReply::NoError) {
            //failure
            qDebug() << "error: " << reply->error();
        }
        else
        { 
            QJsonObject jsonObject= QJsonDocument::fromJson(reply->readAll()).object();
            QHostAddress ip(jsonObject["ip"].toString());
            qDebug() << "external ip: " << ip;

        }
        reply->deleteLater();
        
    });
    return a.exec();
}

JonB

@fadu
So your QNetworkAccessManager networkManager; is a local variable in the pushbutton slot. It is destroyed at the end of that method. I have never used QNAM but I would assume/guess its lifetime must last until after the reply finished signal? If you make your QNetworkAccessManager networkManager a class member variable, or new & delete the instance later, does your code then work?

JonB

@fadu
Does a.exec() return immediately "in GUI app" since you show no window?

fadu

@JonB
No i didn't use it in gui app
this is ui code

 QNetworkAccessManager networkManager;
    QUrl url("https://api.ipify.org");
    //the query used to add the parameter "format=json" to the request
    QUrlQuery query;
    query.addQueryItem("format", "json");
    //set the query on the url
    url.setQuery(query);
    //make a *get* request using the above url
    QNetworkReply* reply = networkManager.get(QNetworkRequest(url));

    QObject::connect(reply, &QNetworkReply::finished,
                     [=](){
        if(reply->error() != QNetworkReply::NoError) {
            //failure
            qDebug() << "error: " << reply->error();
        }
        else
        {
            QJsonObject jsonObject= QJsonDocument::fromJson(reply->readAll()).object();
            QHostAddress ip(jsonObject["ip"].toString());
            qDebug() << "external ip: " << ip;

        }
        reply->deleteLater();

    });

JonB

@fadu
Just checking that the lifetime of QNetworkAccessManager networkManager lasts until finished? Is it e.g. a member variable of some class?

fadu

@JonB
no i put it in new test app there is no classes or anything else just the code above
still same problem
and tried define recieve signal separately

JonB

@fadu
If I understand you right: the first code you posted with the question is actually your working code, in a non GUI-app? You say it's not working in a UI app, then you say you the code is not the same there. It's not great to post code which works, we need to see code which does not.

You second code, for a "GUI" app, does not show a complete program. E.g. it has no main(), it has no a.exec(). Can you show your actual non-working UI program? Or confirm what the lifetime/scope of QNetworkAccessManager networkManager is?

fadu

@JonB
yes totally like you saw
this is gui application code

#include "mainwindow.h"
#include "ui_mainwindow.h"
#include <QJsonObject>
#include <QUrlQuery>
#include <QtNetwork/QNetworkAccessManager>
#include <QtNetwork/QNetworkReply>
#include<QJsonDocument>
#include <QHostAddress>
#include <QHostInfo>
MainWindow::MainWindow(QWidget *parent)
    : QMainWindow(parent)
    , ui(new Ui::MainWindow)
{
    ui->setupUi(this);

}
MainWindow::~MainWindow()
{
    delete ui;
}
void MainWindow::on_pushButton_clicked()
{
    QNetworkAccessManager networkManager;
    QUrl url("https://api.ipify.org");
    //the query used to add the parameter "format=json" to the request
    QUrlQuery query;
    query.addQueryItem("format", "json");
    //set the query on the url
    url.setQuery(query);
    //make a *get* request using the above url
    QNetworkReply* reply = networkManager.get(QNetworkRequest(url));

    QObject::connect(reply, &QNetworkReply::finished,
                     [=](){
        if(reply->error() != QNetworkReply::NoError) {
            //failure
            qDebug() << "error: " << reply->error();
        }
        else
        {
            QJsonObject jsonObject= QJsonDocument::fromJson(reply->readAll()).object();
            QHostAddress ip(jsonObject["ip"].toString());
            qDebug() << "external ip: " << ip;

        }
        reply->deleteLater();
    });
}

JonB

@fadu
So your QNetworkAccessManager networkManager; is a local variable in the pushbutton slot. It is destroyed at the end of that method. I have never used QNAM but I would assume/guess its lifetime must last until after the reply finished signal? If you make your QNetworkAccessManager networkManager a class member variable, or new & delete the instance later, does your code then work?

fadu

@JonB
that's it thank you very much