FHIRModels

FHIRModels is a Swift library for FHIR® resource data models.

Features

• Native Swift representation of FHIR resources, elements and data types
• Separate targets for DSTU2, STU3, R4 and latest build versions
• Enforced non-nullability of mandatory parameters
• Enums for most closed code systems
• Enums to support value[x] types
• Date/Time parsing, validation and conversion to and from NSDate
• Swift Codable support

Requirements

FHIRModels works with Swift 5.1 and newer. Running unit tests requires Swift 5.3 and newer.

Installation

Swift Package Manager is the recommended way to add FHIRModels to your project:

1. In Xcode 11 and newer, go to “File” » “Swift Package Management” » “Add Package Dependency...”
2. Search for “FHIRModels” in the panel that comes up or paste the full URL to the GitHub repository, then select the package
3. Pick the versioning that best works for you (usually the current version and “up to next major”)
4. In order to update the dependency, periodically select “Update to Latest Package Versions” from Xcode 11's “File” » “Swift Package Management” menu

Alternatively, you can add FHIRModels to your Package.swift file as a dependency:

dependencies: [
    .package(url: "https://github.com/apple/FHIRModels.git",
            .upToNextMajor(from: "0.2.0"))
]

Usage

Instantiate FHIR Models

Assuming you have data that you know represents a FHIR resource, you have two options of instantiating a model. We'll assume you have JSON data for the examples below.

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()
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()
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().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

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>?`

Date & Time

FHIRModels handles date/time ↔︎ string conversion transparently and will discard invalid dates.

do {
    let dateTimeString = "2020-03-12T12:33:54.6543-06:00"
    let dateTime = try DateTime(dateTimeString)
    dateTime.date.year == 2020
    dateTime.time.minute == 33
    dateTime.timeZone == TimeZone(secondsFromGMT: -6 * 3600)
} catch {
    print("Failed to parse date time string: \(error)")
}

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Getting Involved

Please feel free to open GitHub issues for questions, suggestions or issues you may have. Because the majority of the codebase is generated we will not be able to accept Pull Requests at this time.

License

This work is APACHE 2.0 licensed.

FHIR® is the registered trademark of HL7 and is used with the permission of HL7. Use of the FHIR trademark does not constitute endorsement of this product by HL7.