type-a

Serdes (Custom Serializers / Deserializers)

When you need a field to deserialize from one type but expose a richer runtime class, use the t.serdes() descriptor.

import { describe, it, expect } from "vitest";
import { Schema, one, typed as t } from "@rybosome/type-a";

describe("Date ISO serdes", () => {
  it("round-trips through JSON", () => {
    const toIso = (d: Date) => d.toISOString();
    const fromIso = (iso: string) => new Date(iso);

    class Event extends Schema.from({
      when: one(t.serdes(Date, t.string), { serdes: [toIso, fromIso] }),
    }) {}

    const iso = "2025-12-31T23:59:59.000Z";
    const e = new Event({ when: iso });
    const json = JSON.parse(JSON.stringify(e));
    expect(json.when).toBe(iso);
    expect(e.when).toBeInstanceOf(Date);
  });
});

serdes pairs work symmetrically – the first function serializes runtime values for JSON, the second parses raw input during construction.

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