Example setting data values from client

[sdr-nz]

Hi - very nice comprehensive library. I not super familiar with opcua but i'm building a client application that will control part of an industrial process.

I need to be able to set variables (setpoints, manipulated variables) on the server/DCS from the client and i'm struggling a bit. I think it would be helpful for folks to see a simple, but well written, example of how data values can be set/written from the client (perhaps from within a control loop).

I've tried to adapt the simple server and client code without success - here's a bit within a client loop:

    let wv = WriteValue {
        node_id: ps.tags.flow_rate_mv.clone(),
        attribute_id: 13, // Value
        index_range: "0".into(),
        //index_range: UAString::default(),
        value: DataValue::value_only(52.0),
    };
    //dbg!(&wv);

    let session = session.write();
    let r = session.write(&[wv]);
    // this result is a long list of error codes
    // which don't help me debug
    dbg!(r);

    // independantly of the above, this works fine
    let value = &session.read(
        &[ReadValueId::from(&ps.tags.flow_rate_mv)],
        TimestampsToReturn::Both,
        2000.0,
    ).unwrap()[0].value;
    dbg!(value.as_ref().unwrap());

My assumption is that the server needs a little code to support this and i'm trying code like this:

/*
        if let Some(ref mut v) = address_space.find_variable_mut(v5_node.clone()) {
            let getter = AttrFnGetter::new(
                move |_, _, _, _, _, _| -> Result<Option<DataValue>, StatusCode> {
                    Ok(Some(DataValue::new_now(50.0)))
                },
            );
            v.set_value_getter(Arc::new(Mutex::new(getter)));
        }
*/
        if let Some(ref mut v) = address_space.find_variable_mut(v5_node.clone()) {
            let setter = AttrFnSetter::new(
                move |_, _, _, _| {
                    println!("setter");
                    Ok(())
                }
            );
            //    move |n, a, r, d| -> Result<(), StatusCode> {
            //        ???.set(n, a, r, d)
            //    },
            //);
            v.set_value_setter(Arc::new(Mutex::new(setter)));
        }

I'm not even able to get the print statement to run - hopefully i'm making some silly mistake. Any help here would be greatly appreciated - thanks -

[sdr-nz]

Update:
To read and write a value from a client 'control' loop, i had to make the following changes on the server. No getters or setters were required.

        let mut v1 = Variable::new(&v1_node, "v1", "v1", 0f64);
        v1.set_writable(true);
        v1.set_user_access_level(UserAccessLevel::CURRENT_READ | UserAccessLevel::CURRENT_WRITE);
        dbg!(&v1.is_writable());
        dbg!(&v1.is_user_writable());
        dbg!(&v1.user_access_level());
        dbg!(&v1.array_dimensions());

        let _ = address_space.add_variables(
            vec![
                v1,
                ...

My loop in the client code looks like this:

    let v1_node = NodeId::new(2, "v1");

    let _session_tx = Session::run_async(session.clone());
    loop {
        {
            let session = session.write();
            let value = session.read(
                &[ReadValueId::from(&v1_node)],
                TimestampsToReturn::Both,
                2000.0,
                ).unwrap();
            dbg!(&value[0]);

            let wv = WriteValue {
                node_id: v1_node.clone(),
                attribute_id: 13,  // Value
                index_range: UAString::default(),  // None
                value: DataValue::value_only(52.0),
            };
            //dbg!(&wv);

            let result = session.write(&[wv]);
            dbg!(result);
        }
        std::thread::sleep(Duration::from_millis(1000));
    }