QNetworkReply issue

Ericode

Hello, I am trying to figure out why I am receiving different numbers each time I print out my reply statement and I want to know what is it printing out?

    params.addQueryItem("username",username);
    params.addQueryItem("password",password);

    QByteArray data;
    data.append(params.toString().mid(1));

    QNetworkRequest request(QUrl("weburl/login.php"));
    request.setHeader(QNetworkRequest::ContentTypeHeader, QVariant("application/x-www-form-urlencoded"));

    QNetworkAccessManager *nam = new QNetworkAccessManager;
    QNetworkReply *reply = nam->get(request);

    qDebug() << reply;

It prints out something like this:
QNetworkReplyImpl(0x412db688d0)
Could someone explain to me why this happens? (The php script works fine for my game and will return something like else echo json_encode(array('status'=>'Login information is incorrect. Check your username and password.')); //wrong password)

JKSH

Hi,

@Ericode said:

Hello, I am trying to figure out why I am receiving different numbers each time I print out my reply statement and I want to know what is it printing out?
    // ...
    QNetworkReply *reply = nam->get(request);

    qDebug() << reply;
It prints out something like this:
QNetworkReplyImpl(0x412db688d0)

In your code, reply is a pointer to a QNetworkReply object. You asked your program to print the value of this pointer, which is the object's memory address. Each time you run your code, the object is created at a different memory address, that's why you see a different value each time.

To get the contents of the network reply, you need to listen for the QNetworkReply::finished() signal. The QNetworkReply object emits this signal when it finishes downloading the data. Connect this signal to a slot that calls QNetworkReply::readAll() -- this gives you the downloaded data.

Remember to delete the QNetworkReply after that, or else you will get a memory leak.

Ericode

@JKSH

    QUrlQuery params;
    params.addQueryItem("username",username);
    params.addQueryItem("password",password);

    QByteArray data;
    data.append(params.toString().mid(1));

    QNetworkRequest request(QUrl("weburl/mmologin.php"));
    request.setHeader(QNetworkRequest::ContentTypeHeader, QVariant("application/x-www-form-urlencoded"));

    QNetworkAccessManager *nam = new QNetworkAccessManager;
    QNetworkReply *reply = nam->get(request);

    connect(reply, SIGNAL(finished()), SLOT(replyFinished(reply)));

This is the updated code along with a new method

void MainWindow::replyFinished(QNetworkReply *reply) {
    qDebug() << "Request Finished";
}

Is this what you ment?

JKSH

@Ericode said:

    connect(reply, SIGNAL(finished()), SLOT(replyFinished(reply)));

This is the updated code along with a new method

void MainWindow::replyFinished(QNetworkReply *reply) {
    qDebug() << "Request Finished";
}

Is this what you ment?

Almost.

Have you used signals and slots before? Your code has the right idea, but it won't work currently because you can't pass a parameter to the slot like that. You have a few options:

Option 1: Store the reply pointer and retrieve it later

void MainWindow::login() {
    // ...
    // "reply" is a member variable of MainWindow
    this->reply = nam->get(request);
    connect(this->reply, SIGNAL(finished()),
            this, SLOT(replyFinished())); // <-- NOTE: You should specify the pointer to the slot owner ("this")
}

void MainWindow::replyFinished() {
    qDebug() << "Request Finished:" << this->reply->readAll();

    // Prevent memory leak
    this->reply->deleteLater();
}

Option 2: Use a C++11 lambda expression to capture the reply pointer

void MainWindow::login() {
    // ...
    // "reply" is a local variable
    QNetworkReply *reply = nam->get(request);
    connect(reply, &QNetworkReply::finished, [=] {
        qDebug() << "Request Finished:" << reply->readAll();

        // Prevent memory leak
        reply->deleteLater();
    });
}

Ericode

@JKSH
Thank you so much for your help. I am glad you showed me both ways to implement this. My only concern now is the QJsonArray. My php is decoding the json array but in qt I am having some issues making one.

 QJsonArray params;
    params[0] = username;
    params[1] = password;

    QNetworkRequest request(QUrl("weburl/mmologin.php"));
    request.setHeader(QNetworkRequest::ContentTypeHeader, QVariant("application/x-www-form-urlencoded"));

    QNetworkAccessManager *nam = new QNetworkAccessManager;
    nam->post(request, params.toString(QUrl::FullyEncoded).toUtf8()); // This line is wrong as QJsonArray does not have a tostring method but I am not sure how else to encode it

    QNetworkReply *reply = nam->get(request);

How would I take params and send it to my web url encoded as a json array?

JKSH

You're welcome :)

@Ericode said:

nam->post(request, params.toString(QUrl::FullyEncoded).toUtf8()); // This line is wrong as QJsonArray does not have a tostring method but I am not sure how else to encode it
...
How would I take params and send it to my web url encoded as a json array?

Embed your QJsonArray in a QJsonDocument first, then call QJsonDocument::toJson().

Ericode

@JKSH
Ok, so I created a QJsonDocument but my issue is calling the QJsonDocument::toJson. How does it know which object I want to covert to json? Also, nam->post(request); only takes one parameter so how would I be able to tell it to send the doc or params along with it?

QJsonArray params;
    params[0] = username;
    params[1] = password;

    QJsonDocument doc;
    doc.setArray(params);
    QJsonDocument::toJson();
nam->post(request);

Ericode

QStringList propertyNames;
QStringList propertyKeys;
QString strReply = (QString)reply->readAll();
QJsonDocument jsonResponse = QJsonDocument::fromJson(strReply.toUtf8());
QJsonObject jsonObject = jsonResponse.object();
QJsonArray jsonArray = jsonObject["properties"].toArray();

foreach (const QJsonValue & value, jsonArray) {
    QJsonObject obj = value.toObject();
    propertyNames.append(obj["PropertyName"].toString());
    propertyKeys.append(obj["key"].toString());
}

I saw something like this online which is similar to what I want but my question is how can I put multiple values in the QJsonArray. Here the values come from QString strReply = (QString)reply->readAll() but I have 2 values I want to go into the json array "username" from the variable username and "password" from the variable password.

JKSH

@Ericode said:

Ok, so I created a QJsonDocument but my issue is calling the QJsonDocument::toJson. How does it know which object I want to covert to json? Also, nam->post(request); only takes one parameter so how would I be able to tell it to send the doc or params along with it?

toJson() turns everything in your QJsonDocument into a JSON string, which you can post to your server.

If you don't want something to be sent, don't add it into your document.

I suggest you inspect the QJsonDocument and the string produced by toJson() using qDebug() -- this should give you useful insight into how the whole thing works.

I also suggest reading this example: http://doc.qt.io/qt-5/qtcore-json-savegame-example.html

Here the values come from QString strReply = (QString)reply->readAll() but I have 2 values I want to go into the json array "username" from the variable username and "password" from the variable password.

Sorry, I don't quite get what you're describing. Could you please post an example of what your final array should look like?

Ericode

@JKSH

{
    "password": "d",
    "username": "d"
}

This is what my json array looks like when it is sent to my php script. Is there way to make it look something like (with the title "Array")?

{
    "Array": [
        true,
        999,
        "string"
    ],
    "Key": "Value",
    "null": null
}

p.s. Does the debug statement below also read echo statements from the php script such as
echo json_encode(array('status'=>'Login information is incorrect. Check your username and password.'));

connect(reply, &QNetworkReply::finished, [=] {
        qDebug() << "Request Finished:" << reply->readAll();
        reply->deleteLater();
    });