How to initialize QJsonObject from QString

You have to follow this step

1. convert Qstring to QByteArray first
2. convert QByteArray to QJsonDocument
3. convert QJsonDocument to QJsonObject

QString str = "{\"name\" : \"John\" }";

QByteArray br = str.toUtf8();

QJsonDocument doc = QJsonDocument::fromJson(br);

QJsonObject obj = doc.object();

QString name = obj["name"].toString();
qDebug() << name;

Use QJsonDocument::fromJson

QString data; // assume this holds the json string

QJsonDocument doc = QJsonDocument::fromJson(data.toUtf8());

If you want the QJsonObject...

QJsonObject ObjectFromString(const QString& in)
{
    QJsonObject obj;

    QJsonDocument doc = QJsonDocument::fromJson(in.toUtf8());

    // check validity of the document
    if(!doc.isNull())
    {
        if(doc.isObject())
        {
            obj = doc.object();        
        }
        else
        {
            qDebug() << "Document is not an object" << endl;
        }
    }
    else
    {
        qDebug() << "Invalid JSON...\n" << in << endl;
    }

    return obj;
}