Tag History Binding Indirect tag addressing help

Ignition
1

Hey Everyone,

Can someone help me with this tag history binding?
Here is what I'm doing:

image
image559×528 26.1 KB

Here is what {view.params.Name}+"/status/encoderposition" evaluates to:
image

I tried building the array in the expression language but it kept complaining about my brackets.

Thank you,
-DG

2

You'll want to define a custom property with this structure:

  • key [array]
    • [0] {object}
      • aggregate value
      • alias value
      • path value
    • [1]{object}
      • aggregate value
      • alias value
      • path value
    • ...

And then bind to it in the expression.

read the Using Dynamic Tag Paths example under this link.

1 Like
3

I guess a better description of my problem is I cant concat in expression language and create a json.
Like this: jsonFormat([{"path": "concat({view.params.Name},"/status/encoderposition")"}])

4

I dont know if there is a better way to do this in the expression language but I built the JSON as a custom property and just bound to it in the tag history expression.
image

It would be nice to do this just in the expression language but i couldn't figure out how to concat a view parameter and build a JSON at the same time.

5

Yeah, the expression language doesn't have any ability to declare a json object or array. We considered it a while back, but decided it wasn't worth the complexity cliff. A custom property is pretty much the way to go here.

6

I'm surprised there isn't something like this:
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I was just surprised to not see an "indirect" radio button. Seems like a necessary addition.