Get Parent (or Parent of Parent) Relative Tag Name

General Discussion
1

In Ignition, is there a way to get the Parent Tag name?

Suppose I have a Tag: (1) A/B0/C and (2) A/B1/C, can I get A/B0 path and A/B1 path from C with the same script (scripted in its UDT class)?

2

Or else, is there any way to get Parent (or Parent of Parent) Relative Tag Parameter?

Here is for illustration:

I have tags with paths like:

A/B0/C/D
A/B1/C/D
A/B2/C/D
A/B3/C/D

Thus, I only need to put Number in my B tags as Data Type Parameter. However, I do not know how to access B Data Type Parameter from D. I could easily get D’s (assuming D is Expression Tag) Data Type Parameters in its Expression like this {Number}, but how to get C’s or B’s?

Since each C is another UDT owned by each B, I don’t know if we could get relative parent Parameters. I know that we could get our own custom parameters which are very useful indeed. But how to get the parent’s (or the parent’s parent’s). Is there a way to automatically pass down this custom parameter to all its children and its children’s children? Like inheritance protected concept in OOP like C# or Java I mean.

Any workaround? :frowning:

3

I am trying to clarify the question here even further (hope it may help. Better question format can be seen here.):

In Ignition, is there a way to get Parent and Parent of Parent relative tag names from an Expression Tag who is a member of a UDT tag in its definition?

Here is the case, I have a UDT tag which contain some other built-in tags, and one of them is an Expression Tag, but the UDT tag is owned by some other higher UDT tag

Something like this (note: all these are in the UDT definition/“template”, not UDT instance):

MyBaseUDTTag
--MyExpressionTag
--SomeOtherTag

And then the MyBaseUDTTag is owned by some other UDT tag

MyAdvanceUDTTag
--MyBaseUDTTagMember
--MyOtherTagMemberInAdvanceUDT

Then, in the MyExpressionTag of MyBaseUDTTag I want to create an expression which is based on its Parent of Parent (that is MyAdvanceUDTTag) custom properties, because in the Tag Browser I have instances of the MyAdvanceUDTTag whose paths are something like this:

BaseFolder/MyAdvanceUDTTagInstance0
BaseFolder/MyAdvanceUDTTagInstance1
BaseFolder/MyAdvanceUDTTagInstance2
BaseFolder/MyAdvanceUDTTagInstance3

Note that there are running numbers from 0-3 there. And I want to make those running number part of the Expression in MyExpressionTag, which - in term of tag paths - are the “child of child” of a particular MyAdvanceUDTTagInstance:

BaseFolder/MyAdvanceUDTTagInstance0/MyBaseUDTTagMember/MyExpressionTag
BaseFolder/MyAdvanceUDTTagInstance1/MyBaseUDTTagMember/MyExpressionTag
BaseFolder/MyAdvanceUDTTagInstance2/MyBaseUDTTagMember/MyExpressionTag
BaseFolder/MyAdvanceUDTTagInstance3/MyBaseUDTTagMember/MyExpressionTag

And so, to avoid definition for each individual tag, I want to make one Expression in the MyExpressionTag Definition/Template instead.

Here, I realize that we could get:

  1. Parent UDT Custom Parameters + InstanceName + TagName
  2. Fellow child’s tag value (that is: SomeOtherTag value)
  3. A particular tag instance value - by specifying the path (which is quite close!)

Option 3. is actually quite close, but unfortunately not what I am looking for. Since what I look for is the name of that Tag - that is, MyAdvanceUDTTagInstance0 name, instead of MyAdvanceUDTTagInstance0 value.

Is there any way to do this in Ignition? I use Ignition v7.8.1 if that matters.

I only need to get Parent path/instance name (as string):

BaseFolder/MyAdvanceUDTTagInstance0/MyBaseUDTTagMember

And (more especially) parent of parent path/instance name:

BaseFolder/MyAdvanceUDTTagInstance0

Having OOP programming background with tools like WinForm, typically there is a way to get Parent Control and its name, and so I am hoping that there might be a similar approach to Ignition Tags too - which I am yet to know.

4

You can use the split and rsplit functions to parse your string into a dataset and then reference the different parts. You can use slicing if you know the lengths too.

There isn’t anything built-in that will do what you want I don’t thing.

s='BaseFolder/MyAdvanceUDTTagInstance0/MyBaseUDTTagMember/MyExpressionTag'

print 'rsplit result'
print s.rsplit("/",1)
print s.rsplit("/",2)
print s.rsplit("/",3)

print 'cutting result'
print s[0:54]
print s[0:10]

There is probably a million ways to parse strings in Python.

1 Like
5

@MMaynardUSG

That seems to be the answer I am looking for! :smiley: thanks, I will check it out.

6

Is there a way to get a Parent Parameter when defining the Child UDT tag?
For instance i have a parameter “Tag Name” on both UDT’s, but i want to access the PARENT “Tag Name” parameter not the Child.

7

In the parent UDT make an expression tag that contains what you need in the child udt tag.
If that is tag name, you can use “{InstanceName}” so it is dynamic and isn’t actually set with a parameter.

Then from the child UDT you can create an expression tag that references {[.]…/parentUDTtagname}

1 Like
8

So you’d have to create an expression tag for every Parent UDT Parameter you are interested in accessing in the Child? That seems pretty excessive when the parameters are already defined.

9

Came across this today but also found that some new Ignition parameters that made this much easier: UDT Parameters | Ignition User Manual

In my case I wanted to get the name of the folder that my UDT was placed in. I'm sure my folder structure will change in the future, so I used the code below to have the UDT calculate what the immediate parent folder would be. Adjust '3' to the correct depth of your tag in your UDT.

split({PathToParentFolder}, "/")[len(split({PathToParentFolder}, '/')) - 3, 0]

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