nlohmann JSON: Object has changed (signal)

[fem_dev]

I'm using a external JSON API called nlohmann JSON inside my Qt GUI Application.
Github link: https://github.com/nlohmann/json

I would like to connect a JSON object to a class method in a way that, every time that this JSON object has changed I receive a signal in a custom slot.

Below I wrote a simple not working example just to illustrate what I would like to do:

void myFunc(nlohman::json& json)
{
    // Update JSON object:
    json["newValue"] = 5;
}

void App::Init()
{
    ....
    nlohman::json myJson;
    ....

    myJson["newValue"] = 0;

    // May be, some connect syntax that I don't know...
    connect(myJson,  nlohman::json::someMethod, this, mySlot)

    myFunc(myJson);
}

void App::mySlot()
{
    qDebug() << "myJson has changed!";
}

So, if I call the App::Init() method, I would like to see the qDebug() output:

myJson has changed!

Is there possible?
If yes, how can I do it?

My system:

• Ubuntu 20.04
• Qt 5.15
• Qt Creator IDE 4.12.3

[Pablo J. Rogina]

@fem_dev you may want to read the signal and slots documentation.
A key requirement for this feature to work is that your class derives from QObject and it has the Q_OBJECT macro in the definition (see small example from documentation)

On the other hand, is a rather compelling reason to use such an external library for JSON when Qt framework does support JSON indeed.

[Pablo J. Rogina]

@fem_dev you may want to read the signal and slots documentation.
A key requirement for this feature to work is that your class derives from QObject and it has the Q_OBJECT macro in the definition (see small example from documentation)

On the other hand, is a rather compelling reason to use such an external library for JSON when Qt framework does support JSON indeed.

[Bonnie]

@fem_dev said in nlohmann JSON: Object has changed (signal):

Is there possible?

I would vote for NO since it doesn't use Qt at all.

[fem_dev]

@Pablo-J-Rogina Thank you...

I know that Qt JSON support...

I'm just using this external JSON API because I'm developing a C++ library that will be bind with PyBind11 library, which will enable to use my C++ library inside the Python environment.

Pybind11: https://github.com/pybind/pybind11

When my C++ library function return a JSON object, the Pybind11 understand the nlohmann JSON object and convert it to a Python dict native type.

So I can use JSON data between C++ Library and Python environment.

I can't do that using the Qt JSON API. Right?

[Pablo J. Rogina]

@fem_dev said in nlohmann JSON: Object has changed (signal):

So I can use JSON data between C++ Library and Python environment.
I can't do that using the Qt JSON API. Right?

I really cannot help with that, i.e. C++ and Python bindings...