Parse jsonarray?

Question

I've got an JSON like the following:

{
    "agentsArray": [{
        "ID": 570,
        "picture": "03803.png",
        "name": "Bob"
    }, {
        "ID": 571,
        "picture": "02103.png",
        "name": "Tina"
    }]
}

Now I'm trying to loop through each array element. Using the qt-json library https://github.com/da4c30ff/qt-json

Tried:

            foreach(QVariantMap plugin, result["agentsArray"].toList()) {
                qDebug() << "  -" << plugin["ID"].toString();
            }

But cannot get it to work, any ideas what I'm doing wrong?

Tinct

Are you using Qt 4 or 5? Qt 5 has json parser classes in QtCore. – Lebrun

That would be awesome! :) – Tinct

Answer 1

I would recommend using the QJson* classes from QtCore in Qt 5. They are very efficient due to the machine readable binary storage optimized for reading and writing, and it is also very convenient to use them due to the nice API they have.

This code base works for me just fine, but please note that I neglected all the error checking for now which is not a good advice for production code. This is just a prototype code, respectively.

main.json

{
    "agentsArray": [{
        "ID": 570,
        "picture": "03803.png",
        "name": "Bob"
    }, {
        "ID": 571,
        "picture": "02103.png",
        "name": "Tina"
    }]
}

main.cpp

#include <QFile>
#include <QByteArray>
#include <QJsonDocument>
#include <QJsonObject>
#include <QJsonArray>
#include <QDebug>

int main()
{
    QFile file("main.json");
    file.open(QIODevice::ReadOnly | QIODevice::Text);
    QByteArray jsonData = file.readAll();
    file.close();

    QJsonDocument document = QJsonDocument::fromJson(jsonData);
    QJsonObject object = document.object();

    QJsonValue value = object.value("agentsArray");
    QJsonArray array = value.toArray();
    foreach (const QJsonValue & v, array)
        qDebug() << v.toObject().value("ID").toInt();

    return 0;
}

main.pro

TEMPLATE = app
TARGET = main
QT = core
SOURCES += main.cpp

Build and Run

qmake && make && ./main

Output

570 
571 

Queenie

Answer 2

output is QByteArray type

QJsonDocument doc(QJsonDocument::fromJson(output));

foreach (const QJsonValue & v, doc.array()){
  Person person;
  person.fromJson(v.toObject());
}

Crosstree