how can i modify the value of the Qjason array?

[CupofCoffee]

hi!
i'm learning Qt and Json.
i've been searching a lot but, i'm still can't modifying json array value.
i'd appreciate your help.

-full json file if you want-
full json file (easyupload link)
https://easyupload.io/jhmklg

---

summary of Json file

{
  "info": {
    "LastSaveTime": "2023-01-25T07:33:44.246Z",
    "TrendInfo": [
      {
        "trendID": 1,
        "trendName": "trendA",
        "trendItems": "apple, banana",
        "trendTerm": 2
      },
      {
        "trendID": 2,
        "trendName": "trendB",
        "trendItems": "bike, motobike",
        "trendTerm": 3
      },
      {
        // .....(trendID 8 is last)
      }
    ]
  },
"TradingAreaInfo": [
   {
      "AreaId": 1,
      "AreaName": "areaA",
      "TrendStatus": [   /*<< I want to update all ["LastTrendTime"] value of this array.*/
        {
          "trendid": 1,
          "LastTrendTime": "22:00"  // <<i want modify this value
        },
       {
          "trendid": 2,
          "LastTrendTime": "21:00"  // <<i want modify this value
        }
        {
           //trendid 8 is last.
        },
       ]
     }, 
   {
      "AreaId": 2,
      "AreaName": "areaB",
      "TrendStatus": [
        {
          "trendid": 1,
          "LastTrendTime": "22:00"
        },
        {
           //trendid 8 is last.
        },
      ]
   },
   {
     //AreaId 14 is last..
   }
  ]
}   

---

and code.

void TrendInUWO::ChangeValueofTable(QTableView* Table, int areaID)
{
    /*get model*/
    QStandardItemModel* model = (QStandardItemModel*)Table->model();
    int areaIDforArr = areaID - 1;
    
    /*get Json file*/
    QJsonDocument Doc = loadJson(FilePath);
    rootObj = Doc.object();
    QJsonObject InfoObj = rootObj["info"].toObject();

    /*change value at 'info->LastSaveTime' ,, it's works*/ 
    InfoObj.insert("LastSaveTime",QJsonValue::fromVariant(QDateTime::currentDateTime().toString(Qt::ISODate)));
    rootObj.insert("info",InfoObj);

    

    TradingAreaInfoArr = rootObj["TradingAreaInfo"].toArray();

    /* get TradingAreaInfo Array[index] Object*/
    QJsonObject TAIObj = TradingAreaInfoArr[areaIDforArr].toObject();   
    /*and get TrendStatus array at TAIObj */
    QJsonArray TrendstatusArr = TAIObj.value("TrendStatus").toArray();

    /* and looping as much as TrendStatusArray size*/
    for (int i = 0; i < TrendstatusArr.size(); ++i)
    {
        /* get value of QTableView's model*/
        QString timestr = model->data(model->index(i, 1)).toString();

        /* and get TrendStatus Array's index Object for modify */
        QJsonObject ArrelementObj =TrendstatusArr[i].toObject();

        /* modify and put it back*/
        ArrelementObj["LastTrendTime"] = timestr;
        TrendstatusArr[i] = ArrelementObj;
    }
    
    /* Appy modified QJsonObject after modify is completed*/
    TAIObj["TrendStatus"] = TrendstatusArr;

    TradingAreaInfoArr[areaIDforArr] = TAIObj; //not working..

    //TradingAreaInfoArr.insert(areaIDforArr,TAIObj); // not working.
    //rootObj["TradingAreaInfo"] = TAIObj; //it works, but delete all other TradingAreaInfo Array..


    //save file.
    Doc.setObject(rootObj);
    saveJson(Doc, FilePath);


    SettingGrid(); //widget refresh
}

---

how can i modify
["LastTrendTime"] value of TrendStatus[all index] in TradingAreaInfo[0] array?

[CupofCoffee]

@CupofCoffee

here is my program

[Juan de Dironne]

This is not the total solution to your problem, but it may help you understand how to iterate through a JSON containing arrays :)

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

int main (int nbArg, char* listArg[])
{
  QFile file("my_another_file.json");
  file.open(QIODevice::ReadOnly);
  QByteArray rawData = file.readAll();
  file.close();

  QJsonDocument docJson = QJsonDocument::fromJson(rawData);
  QJsonObject myRoot = docJson.object();
  QJsonArray TradingAreaInfoList = myRoot.value("TradingAreaInfo").toArray();

  // For Each Trading Area Info
  for(int i=0;i<TradingAreaInfoList.size();i++)
  {
    // Extraction Information
    QJsonObject TradingAreaInfo = TradingAreaInfoList[i].toObject();
    QJsonArray TrendStatusList  = TradingAreaInfo.value("TrendStatus").toArray();

    // For Each Trend Status
    for(int j=0;j<TrendStatusList.size();j++)
    {
      // Extraction Information
      QJsonObject TrendStatus = TrendStatusList[j].toObject();

      qDebug() << TrendStatus["LastTrendTime"];
    }
    // End - For Each Trend Status
  }
  // End - For Each Trading Area Info
}

[JonB]

@CupofCoffee said in how can i modify the value of the Qjason array?:

TradingAreaInfoArr = rootObj["TradingAreaInfo"].toArray();

My understanding is that this returns a copy of the QJsonArray. You can modify that copy (update values, append new ones), but that does not alter the array in the QJsonDocument. The same with the QJsonObject InfoObj = rootObj["info"].toObject(); The objects/arrays in these are read-only.

You have to copy them out as above, alter them, and then replace the current objects/arrays in the document, or create a new one, in order to produce a new document with the updates which can be saved.