[SOLVED] Empty QJsonDocument from file

ningu

Might it be an encoding issue?

ningu

Sorry, that was not completely right:
@QString jsonString = QString::fromUtf8(file.readAll());
qDebug() << jsonString;
@
returns the file contents, while
@qDebug() << QString::fromUtf8(file.readAll())@
returns
@""@

SGaist

Strange, QJsonDocument should handle it...
Did you check what error you got when using fromJson ?

ningu

No, I didn't. How could I do that?

ningu

Ok, I got it. A friend of mine pointed me out that I was looking for the array in the QJsonDocument, and that I should probably be looking for the object, which worked.

The only thing that doesn't work right is that
@QString jsonString = QString::fromUtf8(file.readAll());

QJsonDocument jsonDoc = QJsonDocument::fromJson(jsonString.toUtf8());@
works, but
@QJsonDocument jsonDoc = QJsonDocument::fromJson(file.readAll());@
doesn't.

SGaist

Look at the second parameter of "fromJson":http://qt-project.org/doc/qt-5.0/qtcore/qjsondocument.html#fromJson

From there you can get the error

ningu

It's an 'Illegal value' error. But I get the same error even with an empty file.

SGaist

Could it be your json file encoding that is problematic ?

ningu

That might be it. Is there a way to make sure the file is UTF8? Or set it to UTF8?

SGaist

If you are using QtCreator you could check the editor settings to ensure that it uses UTF8

ningu

Ah, that did it!

Thank you very much for all your help SGaist!

SGaist

You're welcome !

If everything is working now, please update the thread's title to solved so other forum users may know a solution has been found :)

VTiTux

Hi,

I have the same problem, but the solution isn't the UTF8 coding, for me.
QtCreator is already configured to UTF, and that
@ QString jsonString = QString::fromUtf8(file.readAll());

QJsonDocument jsonDoc = QJsonDocument::fromJson(jsonString.toUtf8());

@
don't work for me.

My JSON file is built and written by JsonDocument and QFile, so, it could be valide:
@
bool JSONStorage::storeJSONFile(){
if( !jsonFile.open(QIODevice::WriteOnly | QIODevice::Text | QIODevice::Truncate) ){
return false;
}
QJsonDocument jsonDocument( jsonArray );
jsonFile.write( jsonDocument.toJson() );
jsonFile.close();
return true;
}
@

But I do not manage to load this file. I use this method:
@
void JSONStorage::openJSONFile(){
QJsonParseError parseErr;
QJsonDocument jsonDocument;

if( !jsonFile.open(QIODevice::ReadOnly | QIODevice::Text) ){
    return;
}

jsonDocument.fromJson( jsonFile.readAll(), &parseErr );
qDebug() << parseErr.errorString();
if( jsonDocument.isEmpty()){
    qDebug() << "Empty!";
}
if( jsonDocument.isArray() ){
    qDebug() << "Is array";
    jsonArray = jsonDocument.array();
}

}
@

It says that is empty, and parseErr: "no error occurred"

If I write:
@
qDebug() << jsonFile.readAll();
@

I can see my document. It isn't empty!

What is wrong?

VTiTux

Is it because my main object is an array?

I go to eating and I will retry with an JsonObject to the root, later.

SGaist

Use the second parameter of fromJson(const QByteArray & json, QJsonParseError * error = 0) and check what it returns

VTiTux

Ok

It isn't that:
@
jsonDocument.fromJson( jsonFile.readAll(), &parseErr );
@
but that:
@
jsonDocument = QJsonDocument::fromJson(jsonFile.readAll(), &parseErr );
@

Thanks.

SGaist

Indeed, fromJson is a static function