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How to exit a TRUE FALSE case with a variable without having to specify the False case?

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Dear Labview community,


I got a question that I have frequently encountered, I wonder what is the best solution to this.


Often I need to do an operation to something if a condition is true and there is nothing to do if it is false.


But if I wire that variable.. as in dataflow..then I need to specify what is the false case value. But often I do not need a false case value and it should not be zero either ( as in default if unwired)  for example..


What I tried is simply use a property node of my variable and a sequence as shown in the jpg. Attached VI.


Is there a better way of doing this?


Additional question:

To maintain dataflow with a variable, sometimes I used a similar sequence + error control attached to the property node or error in.


Is there a more elegant way instead of using a sequence + an error control to maintain dataflow?


Bypassing TF case.JPG



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Message 1 of 5
Accepted by topic author rajiv85

As a general rule, it's best to have the controls on the outside of the case structure.

Case Pass Through.png


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Message 2 of 5

Ahhhhh!! Thank you!!! 👍👍

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And since you're fairly new and learning, here's a little bit of the *why*.


One little bit of "tribal knowledge" us old-timers carry is that the LabVIEW compiler is able to do more efficient optimizations when controls and indicators are placed on the base block diagram, not inside any structures.   I think this is especially true if those controls or indicators are assigned as wire-able terminals for the vi.

    It's a fine-tuning detail, which isn't really crucial in a lot of apps, but it isn't bad to learn about and develop good habits early.


So while we're on the topic of fine-tuning, there's another small mod worth considering.  As shown, the False case will read a value from the control and then write the same value back to it via local variable.  It's essentially a no-op.  You might consider coding it that way to make the no-op nature clear.   See the snippet below.

    As for the rule of thumb about putting controls and indicators on the base diagram instead of inside structures, I don't think it applies to local variables, at least not nearly as strongly.



-Kevin P


conditional increment.png

CAUTION! New LabVIEW adopters -- it's too late for me, but you *can* save yourself. The new subscription policy for LabVIEW puts NI's hand in your wallet for the rest of your working life. Are you sure you're *that* dedicated to LabVIEW? (Summary of my reasons in this post, part of a voluminous thread of mostly complaints starting here).
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Message 4 of 5

Thank you very much Kevin for the tips! I got some valuable tips from you many times before on other posts. As soon as I have time I will try to search your previous posts on the forum to learn more from you 😉





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