extensions — Read and write FHIR extensions ergonomically with ExtensionExt

Run with:

cargo run --example extensions

Extensions are a Vec<Extension> keyed by url. The ExtensionExt trait (in the prelude) adds extension(url), extensions(url), set_extension, and add_extension to every resource and datatype that carries them.

The program#

use fhir::prelude::*;
use fhir::r5::choice::Primitive;
use fhir::r5::types::extension::ExtensionValue;

const EYE_COLOR: &str = "http://example.org/fhir/StructureDefinition/eye-color";

fn main() {
    let mut patient = Patient::default();

    // Set an extension (replaces any existing one with the same url).
    patient.set_extension(Extension {
        url: FhirString(EYE_COLOR.to_string()),
        value: Some(ExtensionValue::String(Primitive::new(FhirString(
            "blue".to_string(),
        )))),
        ..Default::default()
    });

    // Read it back by url.
    if let Some(ext) = patient.extension(EYE_COLOR)
        && let Some(ExtensionValue::String(p)) = &ext.value
    {
        println!("eye color: {}", p.value.0);
    }

    // Setting again replaces rather than duplicates.
    patient.set_extension(Extension {
        url: FhirString(EYE_COLOR.to_string()),
        value: Some(ExtensionValue::String(Primitive::new(FhirString(
            "green".to_string(),
        )))),
        ..Default::default()
    });
    println!(
        "extensions with that url: {}",
        patient.extensions(EYE_COLOR).len()
    );

    let json = serde_json::to_string_pretty(&patient).expect("serialize");
    println!("{json}");
}

Source: fhir/examples/extensions.rs in the repository.