How to exploit a json file in QT ?

feedain

Good morning everyone,
I have a project that is to communicate in mqtt with some arduino's(that's ok) but i need to exploit the data (such as the port of arduino or the state : 0 or 1) in JSON format, so i created a json file in my mainwindow.cpp :

       //JSON

       QJsonObject PortObject;
       PortObject.insert("Port", QJsonValue::fromVariant("p"));

       QJsonObject StateObject;
       StateObject.insert("Etat", "e");


       QJsonDocument doc(PortObject);
       qDebug() << doc.toJson();

The first QJsonObject is for which port i want to change his state et the second is to change the state.
I want to know ```
if fromVariant("p"));

StateObject.insert("Etat", "e");

is good as :

with p for the port number and e the state : 0 or 1

And likely to exploit this json file on output application to change a state of a port (for instance).

Thanks everyone.

jsulm

@feedain said in How to exploit a json file in QT ?:

PortObject.insert("Port", QJsonValue::fromVariant("p"));

What is this supposed to do?
Port is a number, right? Not a string. Why not:

PortObject.insert("Port", QJsonValue(p));

?

JonB

@jsulm said in How to exploit a json file in QT ?:

QJsonValue(p)

~~QJsonValue(p).toInt()?~~

jsulm

@JonB said in How to exploit a json file in QT ?:

QJsonValue(p).toInt()?

Why?
insert() expects a QJsonValue.

JonB

@jsulm
I just read your

Port is a number, right? Not a string

If it's supposed to be a number (integer) for a port number i just like to get to converted when i get it from JSON. But not to worry, i think I mis-read what is going on here. I thought it was parsing JSON input, I thing you're talking about setting a JSON value, my bad.

feedain

@feedain said in How to exploit a json file in QT ?:

Good morning everyone,
I have a project that is to communicate in mqtt with some arduino's(that's ok) but i need to exploit the data (such as the port of arduino or the state : 0 or 1) in JSON format, so i created a json file in my mainwindow.cpp :
       //JSON

       QJsonObject PortObject;
       PortObject.insert("Port", QJsonValue::fromVariant("p"));

       QJsonObject StateObject;
       StateObject.insert("Etat", "e");


       QJsonDocument doc(PortObject);
       qDebug() << doc.toJson();
The first QJsonObject is for which port i want to change his state et the second is to change the state.
I want to know

> if fromVariant("p"));

StateObject.insert("Etat", "e");

is good as :

with p for the port number and e the state : 0 or 1

And likely to exploit this json file on output application to change a state of a port (for instance).

Thanks everyone.

jsulm

@feedain
?

feedain

@jsulm said in How to exploit a json file in QT ?:

@feedain
?

yes i modify my error but i want to know how can i exploit this data, for instance if i want to set up : the port 3 to state 1 ?

jsulm

@feedain Please explain better what you want to achieve.
Can you please post JSON document you want to create? So thatb we can actually understand what you are asking.

feedain

@jsulm said in How to exploit a json file in QT ?:

@feedain Please explain better what you want to achieve.
Can you please post JSON document you want to create? So thatb we can actually understand what you are asking.

Okay so, i have some numbers of port on an arduino to use by state : 0 or 1,
Example :

[
    {
            "Port": n, // n is port starts 1 to 55
            "State": e, //e is 0 or 1
        },
]

It's an example but i want to create a JSON like I show you and after that to change easily the port and the state of port
I expect i explain it better...

Christian Ehrlicher

Ignoring the array around the object:

QJsonObject obj;
obj["Port"] = p;
obj["State"] = int(state);

jsulm

@feedain

QJsonObject object;
pbject.insert("Port", QJsonValue(p));
object.insert("Etat", QJsonValue(e));

QJsonArray array;
array.append(object);

QJsonDocument doc(array);
qDebug() << doc.toJson();

You should really take time to read documentation and take a look at examples like: https://doc.qt.io/qt-5/qtcore-serialization-savegame-example.html

feedain

@Christian-Ehrlicher said in How to exploit a json file in QT ?:

Ignoring the array around the object:
QJsonObject obj;
obj["Port"] = p;
obj["State"] = int(state);

obj["Port"] = p; mean you create an array Port and a other State ?

Christian Ehrlicher

@feedain said in How to exploit a json file in QT ?:

obj["Port"] = p; mean you create an array Port and a other State ?

?

feedain

@jsulm said in How to exploit a json file in QT ?:

@feedain
QJsonObject object;
pbject.insert("Port", QJsonValue(p));
object.insert("Etat", QJsonValue(e));

QJsonArray array;
array.append(object);

QJsonDocument doc(array);
qDebug() << doc.toJson();
You should really take time to read documentation and take a look at examples like: https://doc.qt.io/qt-5/qtcore-serialization-savegame-example.html

I look this example but there is some thing that I doesn't understand

Christian Ehrlicher

@feedain said in How to exploit a json file in QT ?:

is some thing that I doesn't understand

And what exactly is the problem? How should we know it when you don't tell us what you don't understand?

feedain

This post is deleted!

feedain

@Christian-Ehrlicher said in How to exploit a json file in QT ?:

@feedain said in How to exploit a json file in QT ?:

is some thing that I doesn't understand

And what exactly is the problem? How should we know it when you don't tell us what you don't understand?

i don't understand on this example how he "create" example. For instance : i create a json file of characters of a game so we have "name" "power" "life"
How do i instanciate a new personnage with this json file ?

JonB

@feedain said in How to exploit a json file in QT ?:

How do i instanciate a new personnage with this json file ?

Do you mean you want an array of "personnage" objects? That was in the sample code above:

QJsonArray array;
array.append(object);

You can keep appending new objects you create, to have as many as you want?

Otherwise, not sure what you mean by "a new personnage with this json file". The file contains whatever it contains, if it contains 10 "personnages" you get 10 personnages. The file does not create further objects, other than whatever is in it. You can create more objects in code, e.g. perhaps by copying some existing personnage object you have read from the file, if that is what you want to do.

jsulm

@feedain You should really be more clear when asking.
"How do i instanciate a new personnage with this json file ?" - do you mean you want to create an instance of a class and initialise its properties from values you read from a JSON file? If so then please tell us what exactly is not clear:

How to read JSON file?
How to initialise an instance of a class?