Qt C++ QNetworkRequest 未发出任何请求

Question

I'm trying to fetch some data from an API using QNetworkRequest following this video ( https://youtu.be/G06jT3X3H9E )

I have a RoR server running on localhost:3000 and I'm trying to fetch something from it.

.h file:

#ifndef WORKER_H
#define WORKER_H

#include <QObject>
#include <QDebug>
#include <QNetworkAccessManager>
#include <QNetworkReply>
#include <QNetworkRequest>
#include <QAuthenticator>
#include <QNetworkProxy>

class Worker : public QObject
{
    Q_OBJECT
public:
    explicit Worker(QObject *parent = nullptr);

signals:

public slots:

    void get(QString code);

private slots:
    void readyRead();
    void authenticationRequired(QNetworkReply *reply, QAuthenticator *authenticator);
    void encrypted(QNetworkReply *reply);
    void finished(QNetworkReply *reply);
    void networkAccessibleChanged(QNetworkAccessManager::NetworkAccessibility accessible);
    void preSharedKeyAuthenticationRequired(QNetworkReply *reply, QSslPreSharedKeyAuthenticator *authenticator);
    void proxyAuthenticationRequired(const QNetworkProxy &proxy, QAuthenticator *authenticator);
    void sslErrors(QNetworkReply *reply, const QList<QSslError> &errors);

private:
    QNetworkAccessManager manager;
};

#endif // WORKER_H

.cpp file:

void Worker::get(QString code)
{
    qInfo() << "Getting something from the server...";
    QNetworkReply* reply = manager.get(QNetworkRequest(QUrl(QString("http://localhost:3000/api/v1/circle_gift_cards/scan?codes=" + code))));
    connect(reply, &QNetworkReply::readyRead, this, &Worker::readyRead);
}

void Worker::readyRead()
{
    qInfo() << "ReadReady";
    QNetworkReply* reply = qobject_cast<QNetworkReply*>(sender());
    if(reply) qInfo() << reply->readAll();
}

The result from:

Worker worker;
worker.get("abc");

is: "Getting something from the server..." it should print "ReadReady" when the request is ready, but I don't think the request is being made, there's nothing in the console either.

---

[Edit 1] What is calling the worker is this

void MainWindow::on_lineEditScanCard_textChanged(QString code) {
    Worker worker(this->site);
    worker.get(code);
}

It's an Edit field(where the user is supposed to type a code

---

[Edit 2]

I removed all app code and did this:

#include <QApplication>
#include "Forms/mainwindow.h"
#include "Requests/worker.h"

int main(int argc, char *argv[]) {
  QApplication a(argc, argv);
  Worker worker;
  worker.get("abc");

  return a.exec();
}

And it worked... Why it does not work when called when the Edit text is changed?

Answer 1

Remember the concepts of scope, life cycle, and local variables? In your case worker is a local variable that will be destroyed instantly so the slot is not invoked, use Worker * worker = new Worker; worker->get("abc"); (remember to delete the memory when you no longer use it)