effect-io-ai

Package: effect
Module: SchemaGetter

SchemaGetter.Getter

Represents a composable transformation from an encoded type E to a decoded type T.

When to use

Use when you need a schema getter to build and compose custom transformations for Schema.decodeTo or Schema.decode.

Details

A getter wraps a function Option<E> -> Effect<Option<T>, Issue, R>. It receives Option.None when the encoded key is absent, such as a missing struct field, and returns Option.None to omit the value from the decoded output. It fails with Issue on invalid input and may require Effect services via R. .map(f) applies f to the decoded value inside Some while leaving None unchanged. .compose(other) chains two getters by feeding the output of this into other; passthrough getters on either side are optimized away.

Example (Creating and composing getters)

import { SchemaGetter } from "effect"

const parseNumber = SchemaGetter.transform<number, string>((s) => Number(s))
const double = SchemaGetter.transform<number, number>((n) => n * 2)
const composed = parseNumber.compose(double)
// composed: Getter<number, string> — parses then doubles

See

• transform to create a getter from a pure function
• passthrough for the identity getter
• transformOrFail for fallible transformation

Signature

declare class Getter<T, E, R> { constructor(
    run: (
      input: Option.Option<E>,
      options: SchemaAST.ParseOptions
    ) => Effect.Effect<Option.Option<T>, SchemaIssue.Issue, R>
  ) }

Source

Since v4.0.0