<A, E, R>(self: Effect<A, E, R>): Effect<Option<A>, never, R>Converts success to Option.some and failure to Option.none.
When to use
Use when you only care whether an effect succeeds and want recoverable
failures represented as Option.none.
Details
Success values become Option.some, recoverable failures become
Option.none, and defects still fail the effect.
Gotchas
option only captures typed, recoverable failures as Option.none.
Defects and interruptions are not captured inside the Option and still
fail the effect.
option also discards typed failure values. Use result if the failure
value matters.
Example (Capturing success or failure as Option)
import { Console, Effect, Option } from "effect"
const program = Effect.gen(function*() {
const someValue = yield* Effect.option(Effect.succeed(1))
const noneValue = yield* Effect.option(Effect.fail("missing"))
yield* Console.log(Option.isSome(someValue))
yield* Console.log(Option.isNone(noneValue))
})
Effect.runPromise(program)
// true
// trueexport const const option: <A, E, R>(
self: Effect<A, E, R>
) => Effect<Option<A>, never, R>
Converts success to Option.some and failure to Option.none.
When to use
Use when you only care whether an effect succeeds and want recoverable
failures represented as Option.none.
Details
Success values become Option.some, recoverable failures become
Option.none, and defects still fail the effect.
Gotchas
option only captures typed, recoverable failures as Option.none.
Defects and interruptions are not captured inside the Option and still
fail the effect.
option also discards typed failure values. Use result if the failure
value matters.
Example (Capturing success or failure as Option)
import { Console, Effect, Option } from "effect"
const program = Effect.gen(function*() {
const someValue = yield* Effect.option(Effect.succeed(1))
const noneValue = yield* Effect.option(Effect.fail("missing"))
yield* Console.log(Option.isSome(someValue))
yield* Console.log(Option.isNone(noneValue))
})
Effect.runPromise(program)
// true
// true
option: <function (type parameter) A in <A, E, R>(self: Effect<A, E, R>): Effect<Option<A>, never, R>A, function (type parameter) E in <A, E, R>(self: Effect<A, E, R>): Effect<Option<A>, never, R>E, function (type parameter) R in <A, E, R>(self: Effect<A, E, R>): Effect<Option<A>, never, R>R>(self: Effect<A, E, R>(parameter) self: {
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; <…;
toString: () => string;
toJSON: () => unknown;
}
interface Effect<out A, out E = never, out R = never>The Effect interface defines a value that lazily describes a workflow or
job. The workflow requires some context R, and may fail with an error of
type E, or succeed with a value of type A.
When to use
Use when you need to represent a lazy, composable workflow that can require
services, fail with a typed error, or succeed with a typed value.
Details
Effect values model resourceful interaction with the outside world,
including synchronous, asynchronous, concurrent, and parallel interaction.
They use a fiber-based concurrency model, with built-in support for
scheduling, fine-grained interruption, structured concurrency, and high
scalability.
To run an Effect value, you need a Runtime, which is a type that is
capable of executing Effect values.
Effect<function (type parameter) A in <A, E, R>(self: Effect<A, E, R>): Effect<Option<A>, never, R>A, function (type parameter) E in <A, E, R>(self: Effect<A, E, R>): Effect<Option<A>, never, R>E, function (type parameter) R in <A, E, R>(self: Effect<A, E, R>): Effect<Option<A>, never, R>R>) => interface Effect<out A, out E = never, out R = never>The Effect interface defines a value that lazily describes a workflow or
job. The workflow requires some context R, and may fail with an error of
type E, or succeed with a value of type A.
When to use
Use when you need to represent a lazy, composable workflow that can require
services, fail with a typed error, or succeed with a typed value.
Details
Effect values model resourceful interaction with the outside world,
including synchronous, asynchronous, concurrent, and parallel interaction.
They use a fiber-based concurrency model, with built-in support for
scheduling, fine-grained interruption, structured concurrency, and high
scalability.
To run an Effect value, you need a Runtime, which is a type that is
capable of executing Effect values.
Effect<type Option<A> = None<A> | Some<A>The Option data type represents optional values. An Option<A> is either
Some<A>, containing a value of type A, or None, representing absence.
When to use
Use to represent initial values that may not yet exist
- Returning from partial functions (not defined for all inputs)
- Managing optional fields in data structures
Namespace containing utility types for Option.
When to use
Use to access type-level helpers associated with Option.
Option<function (type parameter) A in <A, E, R>(self: Effect<A, E, R>): Effect<Option<A>, never, R>A>, never, function (type parameter) R in <A, E, R>(self: Effect<A, E, R>): Effect<Option<A>, never, R>R> = import internalinternal.const option: <A, E, R>(
self: Effect.Effect<A, E, R>
) => Effect.Effect<Option.Option<A>, never, R>