Accessing ContextProperty from cpp

ODБOï

Hello !

Im having troubles to access an object that i putted in my rootContextProperties like this :

/Main.cpp/
MyUaClient client;
engine.rootContext()->setContextProperty("client",&client);
/************/

-Now from my QML files i can access 'client' writing : client.name / client.age...

-But how to access that client instance from an other C++ class ?

Thx in advance for help,

Levon

raven-worx

@LeLev said in Accessing ContextProperty from cpp:

-But how to access that client instance from an other C++ class ?

the same way you've set it.
Means there is also an according getter method available. You can find it in the docs.

ODБOï

Hi @raven-worx thx for the answer ,

I am looking at 'http://doc.qt.io/qt-5/qqmlcontext.html', I can not find anything... Could you please send me a link ?

This is my class where I want to access the rootContextProperty :

class MyUaCallback : public QObject
{
Q_OBJECT
private :
QUrl mainUrl = "main.qml";

public:
MyUaCallback();

/* "static void callback" is the function witch will modify context property */

static void callback(UA_UInt32 handle, UA_DataValue *value, void* context,QUrl url){
    QQmlApplicationEngine* engine = new QQmlApplicationEngine(url);
    //QQmlContext* context = engine->rootContext();

    MyUaClient *cl;
    cl = engine->rootObjects()[0];

    cl->setPlcString1("newStringValue"); // "setPlcString1" is method of 'MyUaClient'
        qDebug()<< "ContextProperty modified";

}

};

But this is not working

Thx for help,
Levon

raven-worx

@LeLev said in Accessing ContextProperty from cpp:

I am looking at 'http://doc.qt.io/qt-5/qqmlcontext.html', I can not find anything... Could you please send me a link ?

Really?! Come on.... QQmlContext::contextProperty()
When you would have at least tried to look over the method summary on the top of the page you would for sure had found it....

ODБOï

@raven-worx thx. Sorry i was looking for something starting with 'get' ...

Eeli K

@LeLev Just like any other object in any C++ object? You have client available in main.cpp so you can do e.g.

MySomethingOther otherObject;
MyUaClient client;
otherObject->setClient(&client);
// set as context property...

or

MyUaClient client;
MySomethingOther* otherObject = new MySomethingOther(&otherObject);
// set as context property...

To have access to an object which have been set as a context property you don't need to use the qml engine or context.

But after seeing your second post I'm confused about what you actually meant and need...

ODБOï

Hello @Eeli-K ,

As i said in the first post, i have a 'client' object instance that i have putted in my rootContextProperties like this :

//
MyUaClient client;
engine.rootContext()->setContextProperty("client",&client);
//
I need this to access my client member variables from QML. OK.

Now i just want to modify my clients member variables from another c++ class, so i need to get that particular client instance..

Is this more clear ?

Thx

Eeli K

@LeLev I believe it's clear, and as I said, it's just another C++ object for your other C++ object and you can bypass the qml engine and contexts altogether. I, for example, have this code:

Tools* tools{new Tools()};
...
QQmlApplicationEngine* engine{new QQmlApplicationEngine()};
    QQmlContext* ctx{engine->rootContext()};
    Connection* conn{new Connection()};
    ProfileData* data{new ProfileData(ctx, conn)};
    Monitoring* monitoring{new Monitoring(conn)};
    CameraController* camera{new CameraController(conn)};

    conn->getNetworks();

    qmlRegisterUncreatableType<CameraController>("eu.vpsystems.software", 1, 0, "CameraController", "Not to be created as QML type");
    ctx->setContextProperty("qApplication", app);
    ctx->setContextProperty("profileData", data);
    ctx->setContextProperty("connection", conn);
    ctx->setContextProperty("tools", tools);
    ctx->setContextProperty("monitoringData", monitoring);
    ctx->setContextProperty("camera", camera);
    engine->load(QUrl(QStringLiteral("qrc:/main.qml")));

Notice how connection is used in the constructors of other objects; it's just a member object for those objects. Each object can be used in QML. The root context is passed to one object because it sets other dynamically created objects as context properties. I don't need to get any object from the root context.

ODБOï

@Eeli-K Thx for help, I know I will be back ^^
sorry im beginner in Qt and not pro in c++