Function addEquality

Adds equality functions to a data object. This freezes an object. HashCode is lazily evaluated and memoized.

This function also acts as an error boundary; you may assume both arguments for equals() are of the same type as the data object, any exceptions thrown by the equality function will be caught and treated as false.

Example

import * as io from "@prelude-io/core";
import { BusOutputType } from "@prelude-io/core";
import { stringHashCode } from "prelude-ts";

const Pet = io.Complex("NestedBus", {
  species: io.string,
  name: io.string,
});

const suku = (
  await Pet.deserialize({ name: "Suku", species: "Cat" })
).getOrThrow() as BusOutputType<typeof Pet>;

const skadi = (
  await Pet.deserialize({ name: "Skadi", species: "Cat" })
).getOrThrow() as BusOutputType<typeof Pet>;

const sukuWithEquality = io.addEquality(
  suku,
  (a, b) => a.name === b.name && a.species === b.species,
  (a) => stringHashCode(a.name + a.species)
);

console.log(sukuWithEquality.equals(suku)); // true
console.log(sukuWithEquality.equals(skadi)); // false

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