|HELP| : How to extract Data from Json file ?

mrjj

Hi and welcome to the forums.
You seem off to a good start.
What you have is a json array with objects in it.

So in you for loop you will get QJsonObject and not a
QJsonValue if i read it correctly :=)
Nope. @JonB is right :)

Pablo J. Rogina

@Elmehdi said in |HELP| : How to extract Data from Json file ?:

I'm new to both Qt and Json

Just in case, have you read the documentation?

There's even a good example...

JonB

@Elmehdi
With all die respect to my learned friend @mrjj, you do get QJsonValues as you iterate through QJsonArray jsonArray.

The point is, a QJsonValue can hold many data types (see https://doc.qt.io/qt-5/qjsonvalue.html#details). In your case those will be QJsonObjects. The first thing you should write in your code is:

foreach (const QJsonValue & value, jsonArray)
{
    qDebug() << value.type();
}

and look at the values per https://doc.qt.io/qt-5/qjsonvalue.html#Type-enum.

From there, you will probably also want to look at QJsonObject QJsonValue::toObject() and/or QVariant QJsonValue::toVariant().

If you know about recursion, that will be pretty handy when parsing JSON data.

mrjj

Hi
I think what confused me is this
QJsonArray jsonArray = json_obj["cases"].toArray();
i dont see "cases" in the data sample.

JonB

@mrjj
I did indeed intend to mention to @Elmehdi : if that is the complete JSON file, nothing there matches with the json_obj["cases"] in your code, I don't know where your idea of the "cases" comes from.

ODБOï

it is not valide json format, you have to delete the semicolon at the end of last lines "activePerOneMillion":66.12,

mrjj

@LeLev
Thats good spotting!

Elmehdi

Thank you guys, I didn't expect the fast answers, that was great. @mrjj sorry there is no field with that name I corrected it.
@JonB I will check that immediately thanks.

Elmehdi

@LeLev you are right I just made a mistake while copying since it was not the whole file it was just a part of it, I fixed it now.

Elmehdi

Thank you all. And a special thanks to @LeLev who helped me in private. apparently the base-ranged for loop helped me since it reconizes the type of objects that are stored in the QjsonArray so it access them all. This was what worked for me:

 QFile countries_file("countries.json");
    QFile morocco_file("morocco.json");
    QString json_string;

    if(countries_file.open(QIODevice::ReadOnly | QIODevice::Text)){
        json_string = countries_file.readAll();
        countries_file.close();
    }
    else
        qDebug()<< "file not found";
    auto json_doc = QJsonDocument::fromJson(json_string.toUtf8());

    QJsonArray jArr = json_doc.array();
QJsonValue val;
    for(auto jsonObj : jArr)
    {
        val = jsonObj.toObject().value("country");
        _country = val.toString();
        qDebug() << "Country: "<< _country;

        val = jsonObj.toObject().value("cases");
        _cases = val.toInt();
        qDebug() << "Cases: "<< _cases;

        val = jsonObj.toObject().value("deaths");
        _deaths = val.toInt();
        qDebug() << "Deaths: "<< _deaths;
   }


        qDebug() << Qt::endl;
        qDebug() << Qt::endl;