<T, E>(f: (e: E) => T): Getter<T, E>Creates a getter that applies a pure function to present values.
When to use
Use when you need a schema getter for a pure, infallible transformation between types.
- Building encode/decode pairs for
Schema.decodeTo.
Details
- This is the most commonly used constructor.
- Transforms
Some(e)toSome(f(e))and leavesNoneunchanged. - Skips
Noneinputs — only called when a value is present. - Never fails.
Example (Transforming strings to numbers)
import { Schema, SchemaGetter } from "effect"
const NumberFromString = Schema.String.pipe(
Schema.decodeTo(Schema.Number, {
decode: SchemaGetter.transform((s) => Number(s)),
encode: SchemaGetter.transform((n) => String(n))
})
)export function function transform<T, E>(
f: (e: E) => T
): Getter<T, E>
Creates a getter that applies a pure function to present values.
When to use
Use when you need a schema getter for a pure, infallible transformation
between types.
- Building encode/decode pairs for
Schema.decodeTo.
Details
- This is the most commonly used constructor.
- Transforms
Some(e) to Some(f(e)) and leaves None unchanged.
- Skips
None inputs — only called when a value is present.
- Never fails.
Example (Transforming strings to numbers)
import { Schema, SchemaGetter } from "effect"
const NumberFromString = Schema.String.pipe(
Schema.decodeTo(Schema.Number, {
decode: SchemaGetter.transform((s) => Number(s)),
encode: SchemaGetter.transform((n) => String(n))
})
)
transform<function (type parameter) T in transform<T, E>(f: (e: E) => T): Getter<T, E>T, function (type parameter) E in transform<T, E>(f: (e: E) => T): Getter<T, E>E>(f: (e: E) => Tf: (e: Ee: function (type parameter) E in transform<T, E>(f: (e: E) => T): Getter<T, E>E) => function (type parameter) T in transform<T, E>(f: (e: E) => T): Getter<T, E>T): class Getter<out T, in E, R = never>class Getter {
run: (input: Option.Option<E>, options: SchemaAST.ParseOptions) => Effect.Effect<Option.Option<T>, SchemaIssue.Issue, R>;
map: <T2>(f: (t: T) => T2) => Getter<T2, E, R>;
compose: <T2, R2>(other: Getter<T2, T, R2>) => Getter<T2, E, R | R2>;
pipe: { <A>(this: A): A; <A, B = never>(this: A, ab: (_: A) => B): B; <A, B = never, C = never>(this: A, ab: (_: A) => B, bc: (_: B) => C): C; <A, B = never, C = never, D = never>(this: A, ab: (_: A) => B, bc: (_: B) => C, cd: (_: C) => D): D; <…;
}
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
Getter<function (type parameter) T in transform<T, E>(f: (e: E) => T): Getter<T, E>T, function (type parameter) E in transform<T, E>(f: (e: E) => T): Getter<T, E>E> {
return function transformOptional<T, E>(
f: (oe: Option.Option<E>) => Option.Option<T>
): Getter<T, E>
Creates a getter that transforms the full Option — both present and absent values.
When to use
Use when you need a schema getter to handle both Some and None cases.
Details
The getter is pure and never fails. It receives the full Option<E> and
must return Option<T>, so it can turn a present value into absent or an
absent value into present.
Example (Filtering out empty strings)
import { Option, SchemaGetter } from "effect"
const skipEmpty = SchemaGetter.transformOptional<string, string>((o) =>
Option.filter(o, (s) => s.length > 0)
)
transformOptional(import OptionOption.map(f: (e: E) => Tf))
}