Model Properties

FHIR Resource and Element types are represented as Swift classes, primitive data types are represented as structs. All primitives are defined as FHIRPrimitive, genericized to the appropriate type such as FHIRBool or DateTime.

Patient with a Name

The library makes extensive use of ExpressibleBy{Type}Literal so you can take shortcuts when instantiating primitives. For example, HumanName.given is an Array of FHIRPrimitive<FHIRString> that can be instantiated as follows:

import ModelsR4

let name = HumanName(family: "Altick", given: ["Kelly"])
let patient = Patient(name: [name])

name.given?.first                   // FHIRPrimitive<FHIRString>?
name.given?.first?.value            // FHIRString?
name.given?.first?.value?.string    // String?

Working with Primitives

You may be tempted to get the Swift native types from primitive values and pass these around. To get a String from the resource ID you would do:

let id = resource.id?.value?.string

Instead, consider passing the element around in its full form, in this case as FHIRPrimitive<FHIRString>. This means you will not lose extensions while you can still use some primitives in code as if they were native types. With FHIRPrimitive<FHIRString> for example, you can actually do:

if resource.id == "101" {
    
}

Conversely, you can also assign many FHIRPrimitive types with String, Bool or numeric literals, for example:

let patient = Patient(...)
patient.id = "101"
patient.active = true

Lastly, many Swift native types have been extended to offer an asFHIR{type}Primitive() method. URL and String for example offer:

let url = URL(string: "http://apple.com")!.asFHIRURIPrimitive()
// url is a `FHIRPrimitive<FHIRURI>`
let str = "http://hl7.org/fhir".asFHIRURIPrimitive()
// str is a `FHIRPrimitive<FHIRURI>?`

Working with Value-X

Some properties on FHIR models can be of different types and will be represented by different keys in the serialized payload, commonly referred to as "value X". These properties are mutually exclusive. As an example, look at MedicationStatement.medicationX, where you can have a Medication either as a reference (medicationReference) or as an inline codeable concept (medicationCodeableConcept).

In FHIRModels, these are modeled as enums to ensure exclusivity, you can work with them as follows:

let med = try decoder.decode(MedicationStatement.self, from: data)
if case .reference(let ref) = med.medication {
    print("--> medication reference display: \(ref.display ?? "{nil}")")
} else if case .codeableConcept(let cc) = med.medication {
    print("--> medication codeable concept text: \(cc.text ?? "{nil}")")
    // Note: you should also look at `cc.coding`
}