effect-io-ai

Package: effect
Module: SchemaTransformation

SchemaTransformation.transformOptional

Creates a Transformation where decode and encode operate on Option values, giving full control over missing-key handling.

When to use

Use when you need a schema transformation to produce or consume Option.None for absent keys.

• You are working with optional struct fields.

Details

• Each function receives Option<input> and returns Option<output>.
• Option.None input means the key is absent; returning Option.None omits the key from the output.
• Pure and synchronous.

Example (Converting an optional key to Option)

import { Option, Schema, SchemaTransformation } from "effect"

const schema = Schema.Struct({
  a: Schema.optionalKey(Schema.Number).pipe(
    Schema.decodeTo(
      Schema.Option(Schema.Number),
      SchemaTransformation.transformOptional({
        decode: Option.some,
        encode: Option.flatten
      })
    )
  )
})

See

• transform — when you don’t need Option-level control
• optionFromOptionalKey — built-in for the common optional-key-to-Option pattern
• optionFromOptional — built-in for optional (undefined) to Option

Signature

declare const transformOptional: <T, E>(options: { readonly decode: (input: Option.Option<E>) => Option.Option<T>; readonly encode: (input: Option.Option<T>) => Option.Option<E>; }) => Transformation<T, E>

Source

Since v4.0.0