System.tag.exists on a Vision Visible Property

Ignition
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1

I'm trying to use the system.tag.exists on an expression for a visible property on certain components part of a faceplate. I can't get this to work. I have a tag path for CO2 level {co2TagPath}. A moving analog indicator that I'd like to hide if the CO2 level tag doesn't exists. I've read through some other posts on this topic and I couldn't find much on using this function in an expression specifically for the visible property. Is this allowed? What is the syntax? If not is there a workaround? I'm using version 8.1.22

2

The expression language is separate from the scripting language and system functions do not work in expressions.

You probably could use the tag quality in the visible expression.

3

For an expression, something like this:

runScript("system.tag.exists", 0, "YourTagPath")
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4

Uh, I never thought of calling system functions with runScript. Interesting.

5

I tried this right before my post. But instead of using a 0 between your commas, I used 1. It locked up my designer. What does the zero represent?

6

That's the time parameter. 0 means it will update only as the tag path changes. 1 means it will try to run every 1 ms, which is why it locked it up.

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7

This worked. Thank you both!

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8

I prefer using the isAvailable expression function provided by @PGriffith 's module Ignition Extensions - Convenience utilities for advanced users

It's far better/faster/more efficient/prettier than using runScript.
There's also isGood provided in the standard igntion platform. isAvailable however checks specifically if the tag is both not disabled and exists. Whereas isGood only checks if it's Good, so will not be good if it has any config errors or other qualities you probably want to know about

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