Stream: fhirpath
Topic: FHIRPath node navigation
David Fallas (May 10 2021 at 01:47):
I am using FHIRPath (C# libraries v3.2.0) to locate target node(s) in a somewhat deeply nested QuestionnaireResponse. When I have found an ITypedElement of interest (using Select(...)), I want to navigate to it's parent and sibling nodes. I haven't yet been able to figure out how to do this. I'd be grateful if someone could point me in the right direction.
Lloyd McKenzie (May 10 2021 at 02:45):
There's no ability to navigate to parents, ancestors or siblings in FHIRPath. What are you trying to do that requires that sort of navigation?
David Fallas (May 11 2021 at 21:50):
@Lloyd McKenzie thanks for the response and apologies for my tardy rejoinder. I have restructured the select string to retrieve the ancestor that I want by having a couple of and predicates.For posterity, the select is "item.descendants().where('{0}'.indexOf($this.linkId) >= 0 and $this.descendants().where('{1}'.indexOf($this.linkId) >= 0 and answer.value=true))" (the two place-holders are lists of Coagulation analytes).
Now that I have the item I want, I have run into problems with the ToPoco<>() call - it throws 'System.MissingMethodException : Cannot create an abstract class'. Any thoughts anyone?
David Fallas (May 12 2021 at 19:19):
OK - I get it, it is the QuestionnaireResponse.ItemComponent that cannot be instantiated. So now that I have the ITypedElement node of interest, it finally dawns on me that I must use the interface to explore the node's Children collection(s). For sure, previous experience with XPath was getting in the way, and I had unwarranted expectations of FHIRPath (put that down to a 'senior moment').
RP (May 12 2021 at 22:08):
(deleted)
Last updated: Apr 12 2022 at 19:14 UTC
