many subscription callbacks

[jbbjarnason]

Looking at the client example: https://github.com/FreeOpcUa/async-opcua/blob/master/samples/simple-client/src/main.rs#L123
The data callback is on subscription level.

While open62541 has data callback on monitored items level, https://github.com/open62541/open62541/blob/6ecfa9500761c681adb8cff9c5b92f5c76a38723/examples/client.c#L121

Is this something that will change, or am I misunderstanding something here?

[einarmo]

We could let you do this, it would be a convenience feature. You can accomplish this with the current implementation, just keep a map from monitored item to data value yourself. I'll see if it is easy to do, it may be a little fiddly to do well with the way we currently do subscriptions on the client.

I find that having lots of callbacks, while common in some languages, tends to run into issues with the borrow checker more easily.