Confusing conditions in parse_reply method

[rouaneta]

I am having troubles reading the CommunicationRequest.requester.agent (please find an example of
payload here).

Our client uses the STU3 version. We call the method use_stu3 on our client. We usually read CommunicationRequest using the syntax FHIR::CommunicationRequest.read("123456"). I realized that to be able to read the attribute requester.agent, I had to use the syntax FHIR::STU3::Communication.read("123456").

Should the method used to parse the fhir payload not be based on the fhir_version of the client in priority ? So that I can call FHIR::CommunicationRequest.read("123456") and the resource will be read correctly according to the client version.

[jawalonoski]

The issue is that the FHIR:: module contains R4 resources only, and the FHIR::STU3:: module contains STU3 resources only, and the FHIR::DSTU2:: module contains DSTU2 resources only.

The client can parse different FHIR versions, but it does not monkey-patch any of the FHIR modules.

So, when you explicitly call FHIR::CommunicationRequest... you are explicitly saying "use R4 CommunicationRequest."

Apologies if this was not obvious or a point of confusion. We hope to improve the documentation and examples for this gem in the future. This should be a topic we cover.

[rouaneta]

Thanks @jawalonoski for the quick reply. The problem is that the behaviour is not the same for each client version. If we look more closely to the parse_reply method:

fhir_client/lib/fhir_client/client.rb

Lines 320 to 338 in 59ccd55

	res = if(@fhir_version == :dstu2 || klass&.ancestors&.include?(FHIR::DSTU2::Model))
	if(format.include?('xml'))
	FHIR::DSTU2::Xml.from_xml(response.body)
	else
	FHIR::DSTU2::Json.from_json(response.body)
	end
	elsif(@fhir_version == :r4 || klass&.ancestors&.include?(FHIR::Model))
	if(format.include?('xml'))
	FHIR::Xml.from_xml(response.body)
	else
	FHIR::Json.from_json(response.body)
	end
	else
	if(format.include?('xml'))
	FHIR::STU3::Xml.from_xml(response.body)
	else
	FHIR::STU3::Json.from_json(response.body)
	end
	end

It appears that the behaviour is as follows (assuming that the format is xml - same behaviour for json):

• case (i) if the client version is dstu2 I would go through FHIR::DSTU2::Xml.from_xml anyway
• case (ii) if the client version is r4 I would go through FHIR::Xml.from_xml , except if I explicitly call FHIR::DSTU2::...Read, in which case I would go through FHIR::DSTU2::Xml.from_xml
• case (iii) if the client version is stu3 it depends only on the module I call the read method on:
  • FHIR::DSTU2::...Read -> FHIR::DSTU2::Xml.from_xml
  • FHIR::...Read -> FHIR::Xml.from_xml
  • FHIR::STU3::...Read -> FHIR::STU3::Xml.from_xml

In other words:

• case (i) The client version takes precedence over the module called
• case (ii) No clear priority between the client version and the module called
• case (iii) The module takes precedence over the client version