<A, E, R>(iterable: Effect.Effect<Iterable<A>, E, R>): Stream<A, E, R>Creates a stream from an effect producing an iterable of values.
When to use
Use when the iterable must be acquired from an Effect before the stream emits, and acquisition services or failures should be part of the stream.
Example (Creating a stream from an iterable effect)
import { Console, Context, Effect, Stream } from "effect"
class UserRepo extends Context.Service<UserRepo, {
readonly list: Effect.Effect<ReadonlyArray<string>>
}>()("UserRepo") {}
const listUsers = Effect.service(UserRepo).pipe(
Effect.andThen((repo) => repo.list)
)
const stream = Stream.fromIterableEffect(listUsers)
const program = Effect.gen(function*() {
const users = yield* stream.pipe(
Stream.provideService(UserRepo, {
list: Effect.succeed(["user1", "user2"])
}),
Stream.runCollect
)
yield* Console.log(users)
})
Effect.runPromise(program)
// Output: [ "user1", "user2" ]constructors
Source effect/Stream.ts:11522 lines
export const const fromIterableEffect: <A, E, R>(
iterable: Effect.Effect<Iterable<A>, E, R>
) => Stream<A, E, R>
Creates a stream from an effect producing an iterable of values.
When to use
Use when the iterable must be acquired from an Effect before the stream emits,
and acquisition services or failures should be part of the stream.
Example (Creating a stream from an iterable effect)
import { Console, Context, Effect, Stream } from "effect"
class UserRepo extends Context.Service<UserRepo, {
readonly list: Effect.Effect<ReadonlyArray<string>>
}>()("UserRepo") {}
const listUsers = Effect.service(UserRepo).pipe(
Effect.andThen((repo) => repo.list)
)
const stream = Stream.fromIterableEffect(listUsers)
const program = Effect.gen(function*() {
const users = yield* stream.pipe(
Stream.provideService(UserRepo, {
list: Effect.succeed(["user1", "user2"])
}),
Stream.runCollect
)
yield* Console.log(users)
})
Effect.runPromise(program)
// Output: [ "user1", "user2" ]
fromIterableEffect = <function (type parameter) A in <A, E, R>(iterable: Effect.Effect<Iterable<A>, E, R>): Stream<A, E, R>A, function (type parameter) E in <A, E, R>(iterable: Effect.Effect<Iterable<A>, E, R>): Stream<A, E, R>E, function (type parameter) R in <A, E, R>(iterable: Effect.Effect<Iterable<A>, E, R>): Stream<A, E, R>R>(iterable: Effect.Effect<Iterable<A>, E, R>(parameter) iterable: {
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;
}
import EffectEffect.type Effect.Effect = /*unresolved*/ anyEffect<import IterableIterable<function (type parameter) A in <A, E, R>(iterable: Effect.Effect<Iterable<A>, E, R>): Stream<A, E, R>A>, function (type parameter) E in <A, E, R>(iterable: Effect.Effect<Iterable<A>, E, R>): Stream<A, E, R>E, function (type parameter) R in <A, E, R>(iterable: Effect.Effect<Iterable<A>, E, R>): Stream<A, E, R>R>): interface Stream<out A, out E = never, out R = never>A Stream<A, E, R> describes a program that can emit many A values, fail
with E, and require R.
Details
Streams are pull-based with backpressure and emit chunks to amortize effect
evaluation. They support monadic composition and error handling similar to
Effect, adapted for multiple values.
Example (Creating and consuming streams)
import { Console, Effect, Stream } from "effect"
const program = Effect.gen(function*() {
yield* Stream.make(1, 2, 3).pipe(
Stream.map((n) => n * 2),
Stream.runForEach((n) => Console.log(n))
)
})
Effect.runPromise(program)
// Output:
// 2
// 4
// 6
Stream<function (type parameter) A in <A, E, R>(iterable: Effect.Effect<Iterable<A>, E, R>): Stream<A, E, R>A, function (type parameter) E in <A, E, R>(iterable: Effect.Effect<Iterable<A>, E, R>): Stream<A, E, R>E, function (type parameter) R in <A, E, R>(iterable: Effect.Effect<Iterable<A>, E, R>): Stream<A, E, R>R> =>
const unwrap: <A, E2, R2, E, R>(
effect: Effect.Effect<Stream<A, E2, R2>, E, R>
) => Stream<
A,
E | E2,
R2 | Exclude<R, Scope.Scope>
>
Creates a stream produced from an Effect.
Example (Unwrapping a stream effect)
import { Console, Effect, Stream } from "effect"
const effect = Effect.succeed(Stream.make(1, 2, 3))
const stream = Stream.unwrap(effect)
const program = Effect.gen(function*() {
const chunk = yield* Stream.runCollect(stream)
yield* Console.log(chunk)
})
// [1, 2, 3]
unwrap(import EffectEffect.map(iterable: Effect.Effect<Iterable<A>, E, R>(parameter) iterable: {
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;
}
const fromIterable: <A>(
iterable: Iterable<A>,
options?: {
readonly chunkSize?: number | undefined
}
) => Stream<A>
Creates a new Stream from an iterable collection of values.
Details
chunkSize: Maximum number of values emitted per chunk.
Example (Creating a stream from an iterable)
import { Console, Effect, Stream } from "effect"
const numbers = [1, 2, 3]
const program = Effect.gen(function*() {
const stream = Stream.fromIterable(numbers)
const values = yield* Stream.runCollect(stream)
yield* Console.log(values)
})
Effect.runPromise(program)
// Output: [ 1, 2, 3 ]
fromIterable))