get json value from api response

[Mr.alaa]

hello everyone i have API where i can get data from json response and it works fine i need to extract only one value i have tried many ways but i can't get it

this the the response i need to get mobile serial value from this response how will it be achieved my code is

QJsonDocument document = QJsonDocument::fromJson(reply->readAll());


               QJsonValue v4 =  document.object().value("TbMobile");
               qDebug() << "v4 = " << v4;

i hope to find answer for that

[Mr.alaa]

thank you for you reply so much and thanks for welcome me here but through this period i have changed my api and now returned what i only need

and i tested it in qt works fine

but when i try to catch serial no way i get undefined

where is the error now why it didn't get it directly.thanks again

[Christian Ehrlicher]

QJsonDocument::fromJson() has a second, optional QJsonParseError parameter which can be used to find out if the document could be parsed correctly. You should check it. http://doc.qt.io/qt-5/qjsondocument.html#fromJson

[Mr.alaa]

can you help me with example that it is the first time to use api

[KillerSmath]

Hi @Mr-alaa and welcome to Qt Forum.

As mentioned by @Christian-Ehrlicher, you can use a ParseError variable to check if you have an error in parse

// in header section
#include <Qfile>
#include <QJsonParseError>
#include <QJsonDocument>
#include <QDebug>

// in body of function
     QByteArray loadData = loadFile.readAll(); // from QFile
     QJsonParseError jsonError;
     QJsonDocument loadDoc = QJsonDocument::fromJson(loadData, &jsonError); // parse and capture the error flag

      if(jsonError.error != QJsonParseError::NoError){ 
        qDebug() << "Error: " << jsonError.errorString();
        //return; 
     }

Okay, you've used the errorParse variable to check if your parse has an error but your json data is sure.
So, we can concentrate in how you should to extract the information from this json.

Note that you are trying to access the data within another dataset, as shown below:

• TbMobile (Object)
  • TbMobileSerial (Array)
    • MobileSerial (String)

You may use 2 ways to access a member of a Json Object

• value(key) function -> object.value(key)
• [] operator -> object[key]

But firstly, the return of these operations is aQJsonValueand this object needs to be converted back to a QJsonObject or QJsonArray, for example.

Suppose you have a json file like that:

{
   "obj1": {
      "name": "A String",
      "value": 2,
      "array" : [
        {
           "id": 152,
           "description": "A small description of element 152"
        },
        {
           "id": 155,
           "description": "A small description of element 155"
        }
      ]
  }
}

And you need to access the description of second element of array object that is a member of obj1.

obj1 -> array[1] -> description

You could to access this information using a similar code:

/// in header section of your file
#include <QJsonDocument>
#include <QJsonValue>
#include <QJsonObject>
#include <QJsonArray>
#include <qDebug>

// in body of your function

     QJsonObject rootObject = loadDoc.object();
     QJsonObject obj1Data = rootObject["obj1"].toObject();
     QJsonArray arrayData = obj1Data["array"].toArray();
     QString description = arrayData[1].toObject()["description"].toString();
     qDebug() << description;
     

The output:
A small description of element 155

I hope i've helped you to solve your doubt. Good studies and good coding.

[Mr.alaa]

thank you for you reply so much and thanks for welcome me here but through this period i have changed my api and now returned what i only need

and i tested it in qt works fine

but when i try to catch serial no way i get undefined

where is the error now why it didn't get it directly.thanks again

[KillerSmath]

@Mr-alaa
It is because your api is returning an array as the root element

[] Delimiter = Array
{} Delimiter = Object

So, you should access the data using:

document.array()[0].toObject().value("mobileSerial").toString();

[Mr.alaa]

Thank you so much for your helping