hl7-2-derive

What it is

Map a struct’s fields to HL7 v2 message paths once, in the type definition, instead of writing the same accessor calls at every call site. You do not depend on this crate directly — it arrives through `hl7-2`’s `derive` feature, which is what keeps the default `hl7-2` build to exactly one dependency.

hl7-2 = { version = "0.2", features = ["derive"] }

Keeping the macros in a crate of their own is what lets the default build of hl7-2 keep exactly one dependency: syn and quote are compiled only for callers who ask for the macros.

Usage

use hl7_2::{FromHl7, ToHl7, Raw};

#[derive(FromHl7, ToHl7)]
struct Admission {
    #[hl7("PID-1")]      sequence: u32,
    #[hl7("PID-3")]      identifiers: Vec<String>,
    #[hl7("PID-5.1.1")]  family_name: String,
    #[hl7("PID-8")]      sex: Option<String>,
    #[hl7(nested)]       visit: Visit,   // its own FromHl7 / ToHl7
    #[hl7(raw)]          raw: Raw,       // the whole message, kept alongside
}

let admission: Admission = hl7_2::parse(text)?.decode()?;
assert_eq!(admission.family_name, "EVERYWOMAN");

// The one vendor field no struct models — same object, no second parse.
assert_eq!(admission.raw.get("ZPD-1")?.as_deref(), Some("local"));

The attributes

One attribute per field.

Field types

Field types convert through hl7_2::FromHl7Value and ToHl7Value: String, bool, the integer and floating-point types, and Option<T> and Vec<T> of those — Option for a value that may be absent, Vec for one that repeats.

A plain type is required, and a path that names nothing is Error::MissingField. Implement hl7_2::FromHl7Text for a domain type of your own and Option and Vec of it follow.

Writing

Writing needs the segments to exist already. Build the message with hl7_2::Builder — whose encode method takes a ToHl7 — or add them with Message::append_segment.

This crate has no spec/index.md of its own: the normative description of struct mode is hl7-2's spec/index.md §6. A fuller walkthrough is in Struct mode and derive.

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