Can't call Evaluate() because fhir.Resource is internal?

[akamili-avey]

Hi,

I've stumbled upon this library and I tried to use it for extracting values from FHIR proto structs, such as in the following sample:

package main

import (
	"fmt"
	"log"

	dpb "github.com/google/fhir/go/proto/google/fhir/proto/r4/core/datatypes_go_proto"
	r4pb "github.com/google/fhir/go/proto/google/fhir/proto/r4/core/resources/patient_go_proto"
	"github.com/verily-src/fhirpath-go/fhirpath"
)

func main() {
	// Create a FHIR Patient resource
	patient := &r4pb.Patient{
		Name: []*dpb.HumanName{
			{
				Given: []*dpb.String{
					{Value: "John"},
				},
				Family: &dpb.String{Value: "Doe"},
			},
		},
	}

	// Compile the FHIRPath expression
	expr := fhirpath.MustCompile("name.given")

	// Pass the patient inside an interface slice
	resources := []*r4pb.Patient{patient}

	// Evaluate the FHIRPath expression
	got, err := expr.Evaluate(resources, []fhirpath.EvaluateOption{}...) // <-- WON'T compile!
	if err != nil {
		log.Fatalf("Evaluation failed: %v", err)
	}

	// Print the result
	fmt.Println("FHIRPath result:", got)
}

It might be because I have not used Golang in a while, but I can't seem to call Evaluate() because it accepts only a []fhir.Resource and fhir.Resource is internal to this package, so I can't access it. Since the[]T does not satisfy []I even when T implements I, I can't make this slice - the compiler won't accept a []r4pb.Patient as an argument to Evaluate(). Or is there something plainly obvious I'm overlooking?

[alexlaurinmath]

Thank you so much for filing this bug! We just picked it up will start working on it soon.

[AlexJSully]

Hi @akamili-avey , a fix has been implemented with v1.2.1 which makes fhirpath.Resource a public type you can utilize.

Given the script you provided, please try

package main

import (
	"fmt"
	"log"

	dpb "github.com/google/fhir/go/proto/google/fhir/proto/r4/core/datatypes_go_proto"
	r4pb "github.com/google/fhir/go/proto/google/fhir/proto/r4/core/resources/patient_go_proto"
	"github.com/verily-src/fhirpath-go/fhirpath"
)

func main() {
	// Create a FHIR Patient resource
	patient := &r4pb.Patient{
		Name: []*dpb.HumanName{
			{
				Given: []*dpb.String{
					{Value: "John"},
				},
				Family: &dpb.String{Value: "Doe"},
			},
		},
	}

	// Compile the FHIRPath expression
	expr := fhirpath.MustCompile("name.given")

	// Pass the patient inside an interface slice
	// Use the `fhirpath.Resource` type
	resources := []fhirpath.Resource{patient}

	// Evaluate the FHIRPath expression
	got, err := expr.Evaluate(resources, []fhirpath.EvaluateOption{}...)
	if err != nil {
		log.Fatalf("Evaluation failed: %v", err)
	}

	// Print the result
	fmt.Println("FHIRPath result:", got)
}