How to use "User Events" in different parts of an application

Question

Hi,
"You programmatically can create and name your own events, called user events, to carry user-defined data. Like queues and notifiers, user events allow different parts of an application to communicate asynchronously. You can handle both user interface and programmatically generated user events in the same Event structure."
What you read was part of labview 7.1 user manual ( Chapter 9 - pg.12 ). I've some problems with the underlined sentence. I hope someone can help me.
When using Queues, the programmer may use a named queue everywhere in the application. there is no need to wire queue reference among VIs or using global variables to store queue reference. the name of the queue will be all that you need. I wonder if it is also possible with a event refnum that is the output of "Register for Event" node. As far as I've tested. the answer is Negative! I tried to copy-paste refnum in front panels and using the same name. but there is no connection between event refnums.
LV User manual claims that user events can be used like queues, but it doesn't seem so.
Does anybody have an idea?
Best Regards.

Answer 1

I didn't look at Damien Gray's presentation recently, but if I remember it correctly, it is on a much higher level than what I meant, because it refers to LARGE application. This is a very simple one.
Using a functional global is not problematic CPU-wise, nor memory wise (unless you get into really big data structures, like hundreds of MBs), so you shouldn't be afraid to use it. I'm also not sure why you're afraid of the loop. The loop is only there to "hold" the USR. It only runs once. If you want, you can replace it with a for loop that runs once. I've recently learned that apparently, you can also get rid of the loop and use a local variable (look at the example called XY chart) instead of a USR. I don't think a local variable should have any more impact than a USR, but that needs to be tested. It can definitely be more convenient for some VIs where you don't have to wire the SR through the entire VI.
Anyway, you will need to have an "obtain ref" VI which will hold a 1D array of names and a corresponding array of refs. Then, you search the array for the name, and if it finds the name, it extracts the correct reference. You will also need a way to input references and names into the array and possibly a way to empty the array. You may need to have 2 levels - the inner VI will be the LV2 VI and the parent will be the obtain ref\fill array\close VI. You will need some error handling as well - what happens if you search for a name and it can't be found and so on...
Hope this helps.
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