AllAccepted answers
Eduard Lebedyuk · May 20

You're welcome. Here's a bit more info about how BPL BPs work. After you compile a BPL BP, two classes get created into the package with the same name as a full BPL class name:

  • Thread1 class contains methods S1, S2, ... SN, which correspond to activities within BPL
  • Context class has all context variables and also the next state which BPL would execute (i.e., S5)

Also BPL class is persistent and stores requests currently being processed.

BPL works by executing S methods in a Thread class and correspondingly updating the BPL class table, Context table, and Thread1 table where one message "being processed" is one row in a BPL table. After the request is processed, BPL deletes the BPL, Context, and Thread entries. Since BPL BPs are asynchronous, one BPL job can simultaneously process many requests by saving information between S calls and switching between different requests.
For example, BPL processed one request till it got to a sync activity - waiting for an answer from BO. It would save the current context to disk, with %NextState property (in Thread1 class) set to response activity S method, and work on other requests until BO answers. After BO answers, BPL would load Context into memory and execute the method corresponding to a state saved in %NextState property.

That's why registered objects as context properties can (and would) be lost between states - as they are not persisted.

Eduard Lebedyuk · May 19

HS.FHIR.DTL.vR4.Model.Resource.Patient is a registered object and not a persistent object, so there's no guarantee it will exist beyond a current BP State. You set context.patient in "Transform 1", so it will be gone from process memory after "Send to FHIR Repo 1" sends the request, but before it gets the reply back.

As a solution you can serialize FHIR resource to json and persist that.

Eduard Lebedyuk · May 8

You can still use classes, just add  %JSONIGNOREINVALIDFIELD to ignore unknown properties:

Parameter %JSONIGNOREINVALIDFIELD As BOOLEAN = 1;

Here's how your example can look like:

Class dc.Item Extends (%RegisteredObject, %JSON.Adaptor)
{

Parameter %JSONIGNOREINVALIDFIELD As BOOLEAN = 1;

Property pureId As %Integer;

Property portalUrl As %VarString;

}

and the main class:

Class dc.Response Extends (%RegisteredObject, %JSON.Adaptor)
{

Parameter %JSONIGNOREINVALIDFIELD As BOOLEAN = 1;

Property items As list Of Item;

/// do ##class(dc.Response).Test()
ClassMethod Test()
{
	set json = ..Sample()
	set obj = ..%New()
	$$$TOE(sc, obj.%JSONImport(json))
	do obj.DisplayItems()
}

Method DisplayItems()
{
	for i=1:1:..items.Count() {
		set item = ..items.GetAt(i)
		zw item
	}
}

ClassMethod Sample() As %String [ CodeMode = expression ]
{
{
  "count": 0,
  "pageInformation": {
    "offset": 0,
    "size": 0
  },
  "items": [
    {
      "pureId": 0,
      "uuid": "196ab1c9-6e60-4000-88cb-4b1795761180",
      "createdBy": "string",
      "createdDate": "1970-01-01T00:00:00.000Z",
      "modifiedBy": "string",
      "modifiedDate": "1970-01-01T00:00:00.000Z",
      "portalUrl": "string",
      "prettyUrlIdentifiers": [
        "string"
      ],
      "previousUuids": [
        "string"
      ],
      "version": "string",
      "startDateAsResearcher": "1970-01-01",
      "affiliationNote": "string",
      "dateOfBirth": "1970-01-01",
      "employeeStartDate": "1970-01-01",
      "employeeEndDate": "1970-01-01",
      "externalPositions": [
        {
          "pureId": 0,
          "appointment": {
            "uri": "string",
            "term": {
              "en_GB": "Some text"
            }
          },
          "appointmentString": {
            "en_GB": "Some text"
          },
          "period": {
            "startDate": {
              "year": 0,
              "month": 1,
              "day": 1
            },
            "endDate": {
              "year": 0,
              "month": 1,
              "day": 1
            }
          },
          "externalOrganization": {
            "uuid": "196ab1c9-6e60-4000-8b89-29269178a480",
            "systemName": "string"
          }
        }
    ]
    }
	]
}.%ToJSON()
}

}
Eduard Lebedyuk · May 8

Something along these lines should work.

ClassMethod ToEnsStream(obj As %RegisteredObject, Output req As Ens.StreamContainer) As %Status
{
	#dim sc As %Status = $$$OK
	try {
		set stream = ##class(%Stream.GlobalCharacter).%New()
		if obj.%Extends("%JSON.Adaptor") {
			$$$TOE(sc, obj.%JSONExportToStream(.stream))
		} elseif obj.%Extends(##class(%DynamicAbstractObject).%ClassName(1)) {
			do obj.%ToJSON(.stream)
		} else {
			/// try %ZEN.Auxiliary.altJSONProvider:%ObjectToAET?
			throw ##class(%Exception.General).%New("<JSON>")
		}
		set req = ##class(Ens.StreamContainer).%New(stream)
	} catch ex {
		set sc = ex.AsStatus()
	}
	quit sc
}