Call by reference into a subpanel won't execute called VIT with a loop

Question

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I've attached a sample program (Main VI.vi) that simply calls a VIT by reference (Subpanel3 VI.vit).  The template simply adds two numbers, but the front panel does NOT show up if there is a loop in the template.  If the loop is removed, everything works fine and of course the template runs fine standalone.  You can verify this by removing the loop, then resaving the template that is called.
Is this a bug or am I missing something?
TR
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Tommy R.
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Attachments:
callByReference.zip ‏15 KB

Answer 1

Hello <<-N->>
In the above example, it is not possible to interact with the subpanel when the 'Wait Until Done' flag is set to TRUE because of how the run VI invoke node is wired to the subpanel invoke node. In this setup, the subpanel invoke node cannot run until the run VI node has finished due to the error wire and VI reference wire that come from the output of the run VI invoke node. Basically the subpanel is waiting on that data before it can run, and if you select the 'Wait Until Done' to be true, then the VI wont continue executing until the VI that was called is finished running. You can refer to this page for help better understanding program dataflow: http://www.ni.com/gettingstarted/labviewbasics/dataflow.htm#Wires
I've attached a picture of how you would construct the VI to be able to interact with the subpanel, while still setting the wait until done flag to TRUE. Note that the subpanel invoke node does not have to wait on the Run VI invoke node before it can run. (This is modified from the Simple Subpanel.VI in the example finder).
I hope this helps!
-Nathan H
Software Developer
National Instruments
Attachments:
subpanel_control.JPG ‏96 KB