How to initialize QJsonObject from QString

Question

I am quite new to Qt and I have a very simple operation that I want to do: I have to obtain the following JSonObject:

{
    "Record1" : "830957 ",
    "Properties" :
    [{
            "Corporate ID" : "3859043 ",
            "Name" : "John Doe ",
            "Function" : "Power Speaker ",
            "Bonus Points" : ["10 ", "45", "56 ", "34", "56", "10 ", "45", "56 ", "34", "56", "10 ", "45", "56 ", "34", "56", "10 ", "45", "56 ", "34", "56", "10 ", "45", "56 ", "34", "56 ", "10", "45 ", "56", "34 ", "56", "45"]
        }
    ]
}

The JSon was checked with this Syntax and Validity checker: http://jsonformatter.curiousconcept.com/ and was found valid.

I used QJsonValue initialization of String for that and converted it to QJSonObject:

QJsonObject ObjectFromString(const QString& in)
{
    QJsonValue val(in);
    return val.toObject();
}

I am loading the JSon pasted up from a file:

QString path = "C:/Temp";
QFile *file = new QFile(path + "/" + "Input.txt");
file->open(QIODevice::ReadOnly | QFile::Text);
QTextStream in(file);
QString text = in.readAll();
file->close();

qDebug() << text;
QJsonObject obj = ObjectFromString(text);
qDebug() <<obj;

There's most certainly a good way to do this because this is not working, and I didn't find any helpful examples

dimakin · Accepted Answer · 2025-01-20 21:11:51Z

60

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;
}

edited Jan 20 at 21:11

dimakin

2,0583 gold badges15 silver badges28 bronze badges

answered Nov 7, 2014 at 15:39

TheDarkKnight

27.6k6 gold badges59 silver badges90 bronze badges

Sign up to request clarification or add additional context in comments.

9 Comments

Ioan Paul Pirau Over a year ago

Thanks for the hint @Merlin069 ! I guess this is the way to make the conversion but so far the doc fails the check and the whole function returns an empty un-initialized object. Did you try the function ?

TheDarkKnight Over a year ago

If it's failing to find the document as an object, then the input string is not formatted correctly according to JSON.

Ioan Paul Pirau Over a year ago

According to this format checher it is valid.

TheDarkKnight Over a year ago

Use QJsonDocument::fromJson, not fromBinaryData - updated answer

TheDarkKnight Over a year ago

@EthanKeller, check your spelling of QJsonDocument !

|

eyllanesc · Accepted Answer · 2019-10-30 08:13:41Z

7

You have to follow this step

convert Qstring to QByteArray first
convert QByteArray to QJsonDocument
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;

edited Oct 30, 2019 at 8:13

eyllanesc

246k19 gold badges205 silver badges282 bronze badges

answered Oct 30, 2019 at 7:02

Joe

8811 gold badge9 silver badges14 bronze badges

Comments

Clive N · Accepted Answer · 2025-01-23 09:41:18Z

0

Assume your json file name is myJsonfile.json, I would go about it this way:

QFile jsonFile(":/myJsonfile.json");
jsonFile.open(QIODevice::ReadOnly | QIODevice::Text);
QByteArray data = jsonFile.readAll();
jsonFile.close();

QJsonParseError jsonError;
const auto document = QJsonDocument::fromJson(data, &jsonError);
if (jsonError.error != QJsonParseError::NoError)
{
    qDebug() << "QJsonDocument::fromJson -> " << jsonError.errorString();
}

answered Jan 23 at 9:41

community wiki

Clive N

Collectives™ on Stack Overflow

How to initialize QJsonObject from QString

3 Answers 3

9 Comments

Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

3 Answers 3

9 Comments

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related