Instantiating FHIR Models

Assuming you have data that you know represents a FHIR resource, you have two options of instantiating a model and an easy option to get typed resources from a Bundle. We'll assume you have JSON data for the examples below.

For added security (protection from stack depth exhaustion), use our provided FHIRDecodingDepthTracker together with JSONDecoder. Easiest way is by using JSONDecoder.fhirModelsReadyDecoder().

1. Use ResourceProxy

The ResourceProxy type inspects the resourceType in the data and instantiates the appropriate class for you:

import ModelsR4

let data = <FHIR JSON data>
let decoder = JSONDecoder.fhirModelsReadyDecoder()
do {
    let proxy = try decoder.decode(ResourceProxy.self, from: data)
    
    let resource = proxy.get()
    // `resource` is a generic `Resource`
    
    let patient = proxy.get(if: Patient.self)
    // `patient` is a nullable `Patient`
    
    if case .patient(let patient) = proxy {
        // `patient` is a `Patient`
    }
    
    switch proxy {
    case .patient(let patient):
        // `patient` is a `Patient`
        break
    default:
        break
    }
} catch {
    print("Failed to instantiate: \(error)")
}

2. Decode to known Resource

If you think you know the correct resource type already:

import ModelsR4

let data = <FHIR JSON data>
let decoder = JSONDecoder.fhirModelsReadyDecoder()
do {
    let resource = try decoder.decode(Patient.self, from: data)
} catch {
    print("Failed to instantiate Patient: \(error)")
}

3. Get resources from Bundle

To get certain resources from a Bundle you can do:

import ModelsR4

let data = <FHIR JSON data>
let bundle = try JSONDecoder.fhirModelsReadyDecoder().decode(ModelsR4.Bundle.self, from: data)
let observations = bundle.entry?.compactMap {
    \$0.resource?.get(if: ModelsR4.Observation.self)
}
// observations is an array of `Observation` instances