Reading Json

[Kris Revi]

    QString jsonStr;
    QString m_DeviceJsonFile("./devices.json");
    QFile file(m_DeviceJsonFile);

    if(QFileInfo::exists(m_DeviceJsonFile))
    {
        file.open(QIODevice::ReadWrite | QIODevice::Text);

        jsonStr = file.readAll();
        file.close();

        QJsonDocument myDock = QJsonDocument::fromJson(jsonStr.toUtf8());
        QJsonObject myObj = myDock.object();

        if (myObj.isEmpty())
        {
            qDebug() << "The Json File Is Empty!";
        }
        else
        {
            for (auto i = myObj.begin(); i != myObj.end(); i++)
            {
                QString myStr = "Key -> " + i.key().toUtf8() + " : Value -> ";
                myStr.append(i.value().toString());
                qDebug() << myStr;
            }
        }

    }

in my json file i have

{
    "Name":"Command1", 
    "icon":"",
    "IPA":"test123",
    "UVLights":false,
    "Status":"online"
},
{
    "Name":"Command2", 
    "icon":"",
    "IPA":"192.168.10.146",
    "UVLights":false,
    "Status":"online"
}

why do i get The Json File Is Empty ?

[JonB]

@Kris-Revi

1. You should at least have verified the file.open(), and printed out jsonStr to be sure.

2. You do not test the result of myDock = QJsonDocument::fromJson(). Read https://doc.qt.io/qt-5/qjsondocument.html#fromJson. Test myDock.isNull(). Pass in an error.

3. Your JSON is not an object. It looks like an array. Is it legal? Don't you have to have:

[
    {
    },
    {
    }
]

?

[Christian Ehrlicher]

@JonB said in Reading Json:

Your JSON is not an object. It looks like an array. Is it legal?

Yes, it's fine but then

QJsonObject myObj = myDock.object();

is wrong. See also QJsonDocument::isArray() and QJsonDocument::isObject()

[JonB]

@Christian-Ehrlicher said in Reading Json:

Yes, it's fine

So JSON allows file of just

{
}

as an object, but if it comes across a comma

{
},
{
}

it changes its mind to an array? Without the []. I didn't know that. So you can append to a JSON file more array items with worrying about the trailing ]?

EDIT I just tried it at http://json.parser.online.fr/ or https://jsonparseronline.com/. It did not allow what you said (SyntaxError: Unexpected token , in JSON at position 3). It requires the [ ... ] around the two objects. So you sure it's legal?

[Kris Revi]

@JonB said in Reading Json:

@Kris-Revi

1. You should at least have verified the file.open(), and printed out jsonStr to be sure.

2. You do not test the result of myDock = QJsonDocument::fromJson(). Read https://doc.qt.io/qt-5/qjsondocument.html#fromJson. Test myDock.isNull(). Pass in an error.

3. Your JSON is not an object. It looks like an array. Is it legal? Don't you have to have:

[
    {
    },
    {
    }
]

?

so i did this

    if (file.open(QIODevice::ReadWrite | QIODevice::Text))
    {
        jsonStr = file.readAll();
        qDebug() << jsonStr;
    }

and got

"{\n    \"Name\":\"Command1\", \n    \"icon\":\"\",\n    \"IPA\":\"test123\",\n    \"UVLights\":false,\n    \"Status\":\"online\"\n},\n{\n    \"Name\":\"Command2\", \n    \"icon\":\"\",\n    \"IPA\":\"192.168.10.146\",\n    \"UVLights\":false,\n    \"Status\":\"online\"\n}

[JonB]

@Kris-Revi
Fine, so you've proved your input is OK.

You need to follow the discussion between @Christian-Ehrlicher and myself. Either way (even if it's illegal but QJsonDocument::fromJson() accepts it), if your input works at all it will be an array, not an object, which is the answer to your question.

[Pablo J. Rogina]

@Christian-Ehrlicher said in Reading Json:

Yes, it's fine but then

It looks like it's not, according to what @JonB have tested online, and what I also checked with the jsonlint website:

Error: Parse error on line 7:

..."Status": "online"}, { "Name": "Comman

----------------------^

Expecting 'EOF', got ','

[Christian Ehrlicher]

@Pablo-J-Rogina A json document can either have an object or array as outer element. @JonB's example validates fine

[
    {
    },
    {
    }
]

But the json why was posted by @Kris-Revi is neither an array nor an object as base so QJsonParser will not parse it.

[JonB]

@Christian-Ehrlicher
Yes indeed. But that is not what you said! When I had said to the OP of his { }, { }

Your JSON is not an object. It looks like an array. Is it legal?

and you said back to me:

Yes, it's fine

[Although I haven't tested, I don't believe the OP's QJsonDocument::fromJson() is returning an array, I believe it is returning an error.]

Anyway, at least now we all seem to be agreeing (right?) that the OP will indeed need [ { }, { } ]. If he wants an array he must enclose it in [ ... ].

[Christian Ehrlicher]

@JonB said in Reading Json:

and you said back to me:

I just forgot to add the Don't you have to have: in my quote :)