[SOLVED]QJsonDocument, QJsonValue, QJsonObject: How To Change Value from File

[doozii]

But thank you for your response JKSH

[doozii]

Sorry, you asked my compiler: Microsoft Visual C++ 11(amd64) and my kit is Desktop Qt 5.2.1 MSVC2012 OpenGL 64 bit.

Here's the full source, Ive tried all your recommendations and nothing works:
@
void MyConfig::configValueChangedHandler(QString name, bool updateVal){
QFile configFile("MyConfig.json");
QString inputData;

if(configFile.open(QIODevice::ReadWrite | QIODevice::Text))
{
    inputData = configFile.readAll();
    QJsonDocument jsonDoc = QJsonDocument::fromJson(inputData.toUtf8());
    QJsonObject jo = jsonDoc.object();
    QJsonValue value = jo.value(QString(name));
    //value = value.toBool(updateVal);

// jo.value(QString(name)) = jo.value(name).toBool(updateVal);
// value = jo.value(QString(name));
// value = value.operator =(updateVal);
//value = updateVal;

// QJsonValue subobj = item[name];
// subobj. = updateVal;

    //item[name] = updateVal;
    configFile.write(jsonDoc.toJson());

    configFile.close();
}

}
@

I've left all the attempts to assign a value back to value in place. Thanks for your help. Still doesnt seem to be a way to assign a value to QJsonValue, or QJsonObject

EDIT: Enclosed code in '@' tags -- JKSH

[JKSH]

Ah, I JUST uninstalled MSVC 2012 from my system yesterday!

Anyway, I made minor modifications to your code to make a fully-standalone program...
@
#include <QFile>
#include <QJsonDocument>
#include <QJsonObject>

int main(int argc, char *argv[])
{
QString name;
bool updateVal;

QFile configFile("MyConfig.json");
QString inputData;

if(configFile.open(QIODevice::ReadWrite | QIODevice::Text))
{
    inputData = configFile.readAll();
    QJsonDocument jsonDoc = QJsonDocument::fromJson(inputData.toUtf8());
    QJsonObject jo = jsonDoc.object();
    QJsonValue value = jo.value(QString(name));
    value = value.toBool(updateVal);
    jo.value(QString(name)) = jo.value(name).toBool(updateVal);
    value = jo.value(QString(name));
    value = value.operator =(updateVal);
    value = updateVal;

// QJsonValue subobj = item[name];
// subobj = updateVal;

// item[name] = updateVal;
configFile.write(jsonDoc.toJson());
configFile.close();
}

return 0;

}
@

...and successfully compiled it with MSVC 2013 64-bit + Qt 5.3.0 beta, as well as MinGW 4.8 32-bit + Qt 5.2.1. The only issues I encountered were warnings about unused variables/parameters.

There's nothing invalid with your code, as far as I can see.

Perhaps some binary files simply got corrupted -- Try starting a new project and creating a minimal example.

[doozii]

LOL... I swear I tried that too... But Ill give it another shot

[doozii]

your code seems like you are doing the same thing over and over... granted Im fairly rusty with my C++ but it seems like 5 lines of code to do where a single @value = updateVal@ should suffice. That doesnt seem efficient to me. Ill let you know if it works

[JKSH]

[quote author="doozii" date="1395837642"]your code seems like you are doing the same thing over and over... granted Im fairly rusty with my C++ but it seems like 5 lines of code to do where a single @value = updateVal@ should suffice. That doesnt seem efficient to me. Ill let you know if it works[/quote]That's your code -- I simply moved it into main() and un-commented lines.

My main point was this: There is no compilation error. All of the different ways to assign something to QJsonValue are valid.

(The actual code I would use is in my first reply, just below your original post)

[doozii]

ohhh I see. yeah I was trying to just use @value = updateVal;@ I left all the commented out lines in to show what i had tried.

[doozii]

So I believe you are correct. I missed your comment about not being able to initialize with pointers and I was passing a pointer. Did not realize it wouldnt work with a reference. I tried again and all of the things I tried seem to work now.

Thank you so much for working through this with me.

[JKSH]

I'm glad you've found a solution :)

All the best with your project!

[doozii]

I got this to compile but there is no value getting written to the QJSonValue and/or the value isnt getting written back to the QJsonDocument. So when I do the @value = val@ and I look at the value variable... its empty.

I wish there was example code for this somewhere or someone would write a book and include JSON handling in it.

[JKSH]

It's not quite a book, but see the official unit tests for a comprehensive suite of JSON assignments/manipulations: http://code.woboq.org/qt5/qtbase/tests/auto/corelib/json/tst_qtjson.cpp.html

How did you look at the QJsonValue?

[doozii]

i did a qWarning() << value.toString(); and a qWarning() << value; Also tried qWarning() << jo[name] and a host of others. All returned as ""

[JKSH]

Code:
@
#include <QJsonDocument>
#include <QJsonObject>
#include <QFile>
#include <QDebug>

int main()
{
QFile file("test.json");
if (file.open(QFile::ReadOnly|QFile::Text))
{
QByteArray jsonText = file.readAll();
file.close();

    QJsonDocument doc = QJsonDocument::fromJson(jsonText);
    qDebug() << doc;

    QJsonObject obj = doc.object();
    qDebug() << obj;

    QJsonValue val = obj["dblValue"];
    qDebug() << val;

    qDebug() << "-----";

    val = 1.61803;
    qDebug() << val;

    obj["dblValue"] = val;
    qDebug() << obj;

    doc.setObject(obj);
    qDebug() << doc;

    if (file.open(QFile::WriteOnly|QFile::Text))
    {
        file.write(doc.toJson());
        file.close();
    }
}

return 0;

}
@

Input file:
@
{
"boolValue": true,
"dblValue": 3.14159,
"strValue": "Hello!"
}
@

Output:
@
QJsonDocument({"boolValue":true,"dblValue":3.1415899999999999,"strValue":"Hello!"})
QJsonObject({"boolValue":true,"dblValue":3.1415899999999999,"strValue":"Hello!"})
QJsonValue(double, 3.14159)

QJsonValue(double, 1.61803)
QJsonObject({"boolValue":true,"dblValue":1.6180300000000001,"strValue":"Hello!"})
QJsonDocument({"boolValue":true,"dblValue":1.6180300000000001,"strValue":"Hello!"})
@