QJsonObject: Access Element tree

[fem_dev]

Looking this JSON example below, how can I access the value of this JSON property called c using Qt 5 JSON API?

{
  "my_array": [
    {
      "a": {
        "b": {
          "c": 10
        }
      }
    },
    {
      "a": {
        "b": {
          "c": 20
        }
      }
    }
  ]
}

I was thinking that could be something like this:

// Get the first object:
int c0 = my_json["my_array"][0]["a"]["b"]["c"].toInt();
// c0 = 10;

// Get the second object:
int c1 = my_json["my_array"][1]["a"]["b"]["c"].toInt();
// c1 = 20;

How can I get this c0 ans c1 values?

[MrShawn]

First you need to use QJsonDocument to get the json from text.

Once you get it into a document, start breaking it apart. From your structure you want an object first. You get the value from your object using your key.

Since it is a little hard to explain here is a small example which could help get you started. I read your JSON from a file test.json and prints out "C0" and "C1" like you are asking.

#include <QApplication>
#include <QFile>
#include <QJsonDocument>
#include <QJsonArray>
#include <QJsonObject>

#include <QDebug>

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
//    MainWindow w;
//    w.show();

    QFile mFile("test.json");
    if (!mFile.open(QIODevice::ReadOnly))
    {
        qDebug() << "Unable to open file";
        return 0;
    }

    QJsonDocument mDoc;
    mDoc = QJsonDocument::fromJson(mFile.readAll());
    if (!mDoc.isObject())
    {
        qDebug() << "JSON not formatted properly or is not an object.";
        return 0;
    }

    qDebug() << mDoc.object().value("my_array").toArray().size();
    
    int c0 = mDoc.object().value("my_array").toArray().at(0).toObject().value("a").toObject().value("b").toObject().value("c").toInt();
    int c1 = mDoc.object().value("my_array").toArray().at(1).toObject().value("a").toObject().value("b").toObject().value("c").toInt();
    qDebug() << c0 << c1;

    return a.exec();
}

[fem_dev]

@mrshawn thank you so much! That's perfect!