Re: How can I obtain a reference to a global variable?
The problem in a nutshell is that I can only access the value of a global variable, but not the properties. With a reference, I can access the properties through a property node. Martin
Re: How can I obtain a reference to a global variable?
Gee, thanks folks. I know that it's a kind of messy way to do something like that, but it works (even if it takes a bunch of clock cycles). For myself, in the long run I'd probably use a functional global. I thought about it afterwards and wasn't sure that I'd put the example together correctly. I tossed it together in the last couple of minutes before leaving for a funeral. I must use LabVIEW too much since I thought about this example a couple of times during the service. I wonder if other people have LabVIEW thoughts while supposedly doing other things. Should we set up a poll? Rob
Re: How can I obtain a reference to a global variable?
Thanks - that was the last bit of the puzzle for me :-) Martin
Re: How can I obtain a reference to a global variable?
Well what do you know - I could upgrade my rating :-) Martin
Re: How can I obtain a reference to a global variable?
There is no way to tell LV that it is a global, it's not - it's as you say a VI with uninitialized shift registers. Why would you want to skip the call? One of the good things about func.globals is the fact that they are VIs; if you try to write to it and it's busy the code will wait the microseconds it takes and then access it. If you add error IO you can use data flow to ensure execution order etc. And you can add all sorts of functionality inside it, much like an object with different methods.
Re: How can I obtain a reference to a global variable?
There seems to be cases where you want to skip the call, see http://zone.ni.com/devzone/conceptd.nsf/webmain/82E60E34E609C22A862569F8007E3F4A?opendocument";>Improving Determinism with Functional Globals, LabVIEW 2-Style Globals, in LabVIEW Real-Time - one of the few documents I found about the topic. But thank you for your answers - standard globals have long been a source of annoyance, since you often want to at a little functionality to them. I only discovered functional globals last week, even though I have been programming LabView since version 3 :-) I would still like to find the answer to the "Skip the call" part, though... Martin
Re: How can I obtain a reference to a global variable?
I would use a functional global instead (generally better than ordinary globals). That global could also hold the reference to the listbox however instead I would just add a method to the func.global that gives you read and write access to the listbox contents. Since it is a global though I would perhaps skip the listbox alltogether though and have a string array, a selection array etc. in the functional global. Then you can read the contents without involving property nodes every time and read it all and present it as a listbox only where that is needed.
Re: How can I obtain a reference to a global variable?
I have searched quite extensively in the LabView documentation and on ni.com to find out more about functional globals, but the information is very sparse. Maybe it's just me overlooking something, but at first sight, it looks simply like a normal subVI with uninitialized shift registers. I can of course make such a VI, but it does not automatically have the "Skip subroutine call if busy" in the context menu. How do I tell LabView to perceive this VI as a functional global? Or is this "Skip subroutine call if busy" a feature of version 7 (I use 6.1)? Martin
Re: How can I obtain a reference to a global variable?
Agreed - in my (twisted?) mind I was just leaving the for a more simple, elegant way to do it - if such a method existed. But you are right, it is certainly not Rob's fault that NI has made it so cumbersome to do. I am therefore upgrading my rating to (I'm not sure I can remove the previous grading, but I'll try to add a few s more... :-) Martin
Re: How can I obtain a reference to a global variable?
Hi Robert, Pretty excellent answer Nirmal
Re: How can I obtain a reference to a global variable?
Hi Martin, Why do you require reference to global variable when it can be accessed directly. I mean is there any advantage by using reference method. I think if u eloboarte your consequences, we can share better. Regards, Nirmal
Re: How can I obtain a reference to a global variable?
Hint: an excellent answer provided with a working example certainly worths a ! (it's four stars rating... not "censored" =A6=AC) It may not be the solution you expected but it is not the poster's fault after all...
Re: How can I obtain a reference to a global variable?
An excellent answer. Exactly what I was looking for. I had wondered if it could be done along those lines, but did not know enough about the "To more specific class" function to nail it myself. Pity that it is not possible to do this directly (i.e. right-click a global variable and select "Create > Reference" or "Create > Property node").
Re: How can I obtain a reference to a global variable?
Thank you for your answer. I know how to use global variables in general, but the problem is that a Multicolumn Listbox (MCL) referred as a global is just the number of the selected line(s). I would like to access the contents of the MCL, which I perceive as a table. If this is a MCL in a normal VI, I can create a reference (and by this I mean a reference, not a local variable), and use a property node to access the ItemNames property, which gives me the contents of the table (I could of course also have created the property node directly, but the reference can be passed to subVIs). However, if the MCL is a global variable, it is unclear how I can create a reference or property node to access the contents. Is this impossible, or is there something that I overlooked? Martin
Re: How can I obtain a reference to a global variable?
Hi, For changing the contents of any gloabal variable, you have to access that global variable in a normal vi. Open a new vi, go to Block diagram -> Function Pallete->Structure-> Global variable. Then right click on this global variable-> replace by your global variable vi or create a new global variable vi. By doing this, u can access the value and can change it. Hope it helps. Your feedbacks are welcome. Best Regards, Nirmal Sharma
