set the value of a process variable in an expression

RE: set the value of a process variable in an expression

Mike Schmitt — Tue, 09 Feb 2021 14:59:58 GMT

Ah i see. No, the way you've done it is the correct way. I've wished at times for the ability to update multiple PVs based on one expression (such as an expression that runs an expensive calculation, and i want to just run it once and save various aspects of the result to different PVs). The only real alternative here is to run the expensive operation in an input variable (which sucks since input variable expressions STILL collapse the expression code they contain down to one line, upon saving...), then refer to that ACP in the different output expressions. But even this still does require one output entry added for each PV you want to write into.

RE: set the value of a process variable in an expression

erikb0001 — Tue, 09 Feb 2021 09:13:48 GMT

Hello Mike,

What I am trying to accomplish is to set the value of multiple pv's based on the value of 1 other pv. Then the values of the multiple pv's will be used/configured in the doc from template service.
No I configured one expression for each pv separately in the nodeouput of a scriptask to save the value. So wanted to know if it is possible to update all the pv's in one expression.

Kind Regards,

Erik

RE: set the value of a process variable in an expression

Mike Schmitt — Mon, 08 Feb 2021 15:00:58 GMT

Can you give a bit more clarification as to what you're trying to accomplish, then?

RE: set the value of a process variable in an expression

erikb0001 — Mon, 08 Feb 2021 07:20:03 GMT

Thank you Mike.
I wanted to know if it was possible not use the node outputs to make it more dynamic.
The Apple and colors was an example to illustrate my question.

Kind Regards,

Erik

RE: set the value of a process variable in an expression

Mike Schmitt — Sun, 31 Jan 2021 17:46:29 GMT

I guess it depends on what exactly you want to do. If you want to set the value of pv!color to "green" when fruit is "apple", but otherwise not change the value of pv!color, you would simply set the following expression in your script task to save into pv!color:

if(
  pv!fruit = "Apple",
  "green",
  pv!color
)

RE: set the value of a process variable in an expression

erikb0001 — Sun, 31 Jan 2021 13:46:34 GMT

Hi Chris,

Thanks for you answer.
Now I know that there is no other way, I will use the node outputs in a scripttask to set the variables based on the expression with the condition.

Kind Regards.

Erik

RE: set the value of a process variable in an expression

Chris — Sat, 30 Jan 2021 15:52:58 GMT

No, you cannot achieve this as in your code posted above - process variables will be updated on the data tab, node input or outputs. What is your use case / where are you attempting to run this expression?