Simple HTTP request in QNetworkAccessManager doesn't work

BlueManCZ

I'm trying to implement simple HTTP request with QNetworkAccessManager, but it does nothing. Code compiles and runs fine, but my method connected to &QNetworkAccessManager::finished seems to be never called. Connect itself returns true.

I have this code:

main.cpp

#include <iostream>
#include <QApplication>
#include "main.h"

MyObject::MyObject(QObject* parent) {
    manager = new QNetworkAccessManager(parent);
}

void MyObject::TestConnection() {
    auto status = connect(manager, &QNetworkAccessManager::finished, this, &MyObject::ReplyFinished);
    qDebug() << "Connection status:" << status;

    manager->get(QNetworkRequest(QUrl("https://google.com")));
}

void MyObject::ReplyFinished(QNetworkReply *reply) {
    QString answer = reply->readAll();
    qDebug() << answer;
}

int main(int argc, char *argv[]) {
    auto *app = new QApplication(argc, argv);
    auto myObject = new MyObject(app);
    myObject->TestConnection();
    return 0;
}

main.h

#include <QtNetwork/QNetworkAccessManager>
#include <QtNetwork/QNetworkReply>

class MyObject : public QObject {
Q_OBJECT
public:
    MyObject(QObject* parent);
    void TestConnection();
    void ReplyFinished(QNetworkReply *reply);

    QNetworkAccessManager *manager;
};

Is there something wrong? I walked through a bunch of forums and guides and tried multiple ways to get this working:

connected SIGNALS and SLOTS
binded finished(), readyRead() on reply object
used lambda expression instead of method reference
tried HTTP and HTTPS with different domains

I'm building this in CLion on Linux with CMake, can it be related? Maybe this code will work for you and there is a problem with my platform.

CMakeLists.txt

cmake_minimum_required(VERSION 3.17)
project(http)

set(CMAKE_CXX_STANDARD 20)
set(CMAKE_AUTOMOC ON)

add_executable(http main.cpp main.h)

find_package(Qt5Widgets REQUIRED)
find_package(Qt5Network REQUIRED)

target_link_libraries(${PROJECT_NAME} Qt5::Widgets Qt5::Network)

Thank you in advance.

fcarney

In our code:

QNetworkReply *reply = manager->get(QNetworkRequest(QUrl("https://google.com")));
connect(reply, SIGNAL(finished()), reply, SLOT(deleteLater()));
connect(reply, SIGNAL(finished()), this, SLOT(reply_finished()));

BlueManCZ

I found out what is wrong. I forgot to execute an application object. The program finishes faster then the response can actually arrive.

Replacing return 0; with return app->exec(); in main() did the trick.

Can I somehow wait for the response and then exit a program?

fcarney

@BlueManCZ You can call quit on the app while it is in the event loop. So in reply finished I think you can call

QCoreApplication::quit(); // static call

BlueManCZ

Thank you, you are right. Calling QApplication::quit(); at the end of ReplyFinished method works.