effect-io-ai

Package: effect
Module: Match

Match.discriminatorStartsWith

Matches values where a specified field starts with a given prefix.

When to use

Use to match string discriminator values by prefix instead of exact value.

Details

Instead of checking for exact matches, this helper matches values that share a common prefix. For example, if the discriminant field contains hierarchical names like "A", "A.A", and "B", a single "A" rule can match both "A" and "A.A".

Example (Matching discriminator prefixes)

import { Match, pipe } from "effect"

const match = pipe(
  Match.type<{ type: "A" } | { type: "B" } | { type: "A.A" } | {}>(),
  Match.discriminatorStartsWith("type")("A", (_) => 1 as const),
  Match.discriminatorStartsWith("type")("B", (_) => 2 as const),
  Match.orElse((_) => 3 as const)
)

console.log(match({ type: "A" })) // 1
console.log(match({ type: "B" })) // 2
console.log(match({ type: "A.A" })) // 1

See

• discriminator for matching exact discriminator values

Signature

declare const discriminatorStartsWith: <D extends string>(field: D) => <R, P extends string, Ret, Fn extends (_: Extract<R, Record<D, `${P}${string}`>>) => Ret>(pattern: P, f: Fn) => <I, F, A, Pr>(self: Matcher<I, F, R, A, Pr, Ret>) => Matcher<I, Types.AddWithout<F, Extract<R, Record<D, `${P}${string}`>>>, Types.ApplyFilters<I, Types.AddWithout<F, Extract<R, Record<D, `${P}${string}`>>>>, A | ReturnType<Fn>, Pr, Ret>

Source

Since v4.0.0