<A, E, R>(self: Effect<A, E, R>): Effect<
Option<A>,
Exclude<E, Cause.NoSuchElementError>,
R
>Catches NoSuchElementError failures and converts them to Option.none.
When to use
Use when you expect missing-value failures and want them to become an optional success while all other failures keep failing.
Details
Success values become Option.some, NoSuchElementError becomes
Option.none, and all other errors are preserved.
Example (Recovering from missing Option values)
import { Effect, Option } from "effect"
const some = Effect.fromNullishOr(1).pipe(Effect.catchNoSuchElement)
const none = Effect.fromNullishOr(null).pipe(Effect.catchNoSuchElement)
Effect.runPromise(some).then(console.log) // { _id: 'Option', _tag: 'Some', value: 1 }
Effect.runPromise(none).then(console.log) // { _id: 'Option', _tag: 'None' }export const const catchNoSuchElement: <A, E, R>(
self: Effect<A, E, R>
) => Effect<
Option<A>,
Exclude<E, Cause.NoSuchElementError>,
R
>
Catches NoSuchElementError failures and converts them to Option.none.
When to use
Use when you expect missing-value failures and want them to become an
optional success while all other failures keep failing.
Details
Success values become Option.some, NoSuchElementError becomes
Option.none, and all other errors are preserved.
Example (Recovering from missing Option values)
import { Effect, Option } from "effect"
const some = Effect.fromNullishOr(1).pipe(Effect.catchNoSuchElement)
const none = Effect.fromNullishOr(null).pipe(Effect.catchNoSuchElement)
Effect.runPromise(some).then(console.log) // { _id: 'Option', _tag: 'Some', value: 1 }
Effect.runPromise(none).then(console.log) // { _id: 'Option', _tag: 'None' }
catchNoSuchElement: <function (type parameter) A in <A, E, R>(self: Effect<A, E, R>): Effect<Option<A>, Exclude<E, Cause.NoSuchElementError>, R>A, function (type parameter) E in <A, E, R>(self: Effect<A, E, R>): Effect<Option<A>, Exclude<E, Cause.NoSuchElementError>, R>E, function (type parameter) R in <A, E, R>(self: Effect<A, E, R>): Effect<Option<A>, Exclude<E, Cause.NoSuchElementError>, 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>, Exclude<E, Cause.NoSuchElementError>, R>A, function (type parameter) E in <A, E, R>(self: Effect<A, E, R>): Effect<Option<A>, Exclude<E, Cause.NoSuchElementError>, R>E, function (type parameter) R in <A, E, R>(self: Effect<A, E, R>): Effect<Option<A>, Exclude<E, Cause.NoSuchElementError>, 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>, Exclude<E, Cause.NoSuchElementError>, R>A>, type Exclude<T, U> = T extends U
? never
: T
Exclude from T those types that are assignable to U
Exclude<function (type parameter) E in <A, E, R>(self: Effect<A, E, R>): Effect<Option<A>, Exclude<E, Cause.NoSuchElementError>, R>E, import CauseCause.type Cause.NoSuchElementError = /*unresolved*/ anyNoSuchElementError>, function (type parameter) R in <A, E, R>(self: Effect<A, E, R>): Effect<Option<A>, Exclude<E, Cause.NoSuchElementError>, R>R> = import internalinternal.const catchNoSuchElement: <A, E, R>(
self: Effect.Effect<A, E, R>
) => Effect.Effect<
Option.Option<A>,
Exclude<E, Cause.NoSuchElementError>,
R
>