I want store my datas in JSON file like:
{ "plottingData": [ { "min": 17, "max": 35, "mean": 20 }, { "min": 7, "max": 35, "mean": 17 }, { "min": 8, "max": 50, "mean": 29 } ] } How can I create this struct? I used to QJsonObject but I couldn't add QJsonArray like this.
From Qt documentation:
QJsonArray plot_array; // use initializer list to construct QJsonObject auto data1 = QJsonObject( { qMakePair(QString("min"), QJsonValue(17)), qMakePair(QString("max"), QJsonValue(35)), qMakePair(QString("mean"), QJsonValue(20)) }); plot_array.push_back(QJsonValue(data1)); // Or use insert method to create your QJsonObject QString min_str("min"); QString max_str("max"); QString mean_str("mean"); for(auto item : your_collection) { QJsonObject item_data; item_data.insert(min_str, QJsonValue(item.min)); item_data.insert(max_str, QJsonValue(item.max)); item_data.insert(mean_str, QJsonValue(item.mean)); plot_array.push_back(QJsonValue(item_data)); } QJsonObject final_object; final_object.insert(QString("plottingData"), QJsonValue(plot_array)); 
QJsonObject, QJsonArray and QJsonValue for more info and their usages. QJsonObject o1 { { "min", 17 }, { "max", 35 }, { "mean", 20 }, }; QJsonObject o2; o2 [ "min" ] = 7; o2 [ "max" ] = 35; o2 [ "mean"] = 17; QJsonArray arr; arr.append ( o1 ); arr.append ( o2 ); QJsonObject obj; obj [ "plottingData" ] = arr; //to see the JSON output QJsonDocument doc ( obj ); qDebug() << doc.toJson ( QJsonDocument::Compact ); // or QJsonDocument::Indented // output: "{\"plottingData\":[{\"max\":35,\"mean\":20,\"min\":17},{\"max\":35,\"mean\":17,\"min\":7}]}" 