<K, A, E>(
self: FiberMap<K, A, E>,
key: K,
options?:
| {
readonly onlyIfMissing?: boolean | undefined
readonly propagateInterruption?: boolean | undefined
readonly startImmediately?: boolean | undefined
}
| undefined
): <R, XE extends E, XA extends A>(
effect: Effect.Effect<XA, XE, R>
) => Effect.Effect<Fiber.Fiber<XA, XE>, never, R>
<K, A, E, R, XE extends E, XA extends A>(
self: FiberMap<K, A, E>,
key: K,
effect: Effect.Effect<XA, XE, R>,
options?:
| {
readonly onlyIfMissing?: boolean | undefined
readonly propagateInterruption?: boolean | undefined
readonly startImmediately?: boolean | undefined
}
| undefined
): Effect.Effect<Fiber.Fiber<XA, XE>, never, R>Forks an Effect and stores the resulting fiber in the FiberMap under a key.
Details
When the fiber completes, it is removed from the map. If the key already has
a fiber, the previous fiber is interrupted unless onlyIfMissing is set.
Example (Forking effects into a map)
import { Effect, Fiber, FiberMap } from "effect"
const program = Effect.gen(function*() {
const map = yield* FiberMap.make<string>()
// Run effects and add the fibers to the map
const fiber1 = yield* FiberMap.run(map, "task1", Effect.succeed("Hello"))
const fiber2 = yield* FiberMap.run(map, "task2", Effect.succeed("World"))
// Join the fibers to get their successful values
const result1 = yield* Fiber.join(fiber1)
const result2 = yield* Fiber.join(fiber2)
console.log(result1, result2) // "Hello", "World"
console.log(yield* FiberMap.size(map)) // 0 (fibers are removed after completion)
})export const const run: {
<K, A, E>(
self: FiberMap<K, A, E>,
key: K,
options?:
| {
readonly onlyIfMissing?:
| boolean
| undefined
readonly propagateInterruption?:
| boolean
| undefined
readonly startImmediately?:
| boolean
| undefined
}
| undefined
): <R, XE extends E, XA extends A>(
effect: Effect.Effect<XA, XE, R>
) => Effect.Effect<
Fiber.Fiber<XA, XE>,
never,
R
>
<K, A, E, R, XE extends E, XA extends A>(
self: FiberMap<K, A, E>,
key: K,
effect: Effect.Effect<XA, XE, R>,
options?:
| {
readonly onlyIfMissing?:
| boolean
| undefined
readonly propagateInterruption?:
| boolean
| undefined
readonly startImmediately?:
| boolean
| undefined
}
| undefined
): Effect.Effect<Fiber.Fiber<XA, XE>, never, R>
}
Forks an Effect and stores the resulting fiber in the FiberMap under a key.
Details
When the fiber completes, it is removed from the map. If the key already has
a fiber, the previous fiber is interrupted unless onlyIfMissing is set.
Example (Forking effects into a map)
import { Effect, Fiber, FiberMap } from "effect"
const program = Effect.gen(function*() {
const map = yield* FiberMap.make<string>()
// Run effects and add the fibers to the map
const fiber1 = yield* FiberMap.run(map, "task1", Effect.succeed("Hello"))
const fiber2 = yield* FiberMap.run(map, "task2", Effect.succeed("World"))
// Join the fibers to get their successful values
const result1 = yield* Fiber.join(fiber1)
const result2 = yield* Fiber.join(fiber2)
console.log(result1, result2) // "Hello", "World"
console.log(yield* FiberMap.size(map)) // 0 (fibers are removed after completion)
})
run: {
<function (type parameter) K in <K, A, E>(self: FiberMap<K, A, E>, key: K, options?: {
readonly onlyIfMissing?: boolean | undefined;
readonly propagateInterruption?: boolean | undefined;
readonly startImmediately?: boolean | undefined;
} | undefined): <R, XE extends E, XA extends A>(effect: Effect.Effect<XA, XE, R>) => Effect.Effect<Fiber.Fiber<XA, XE>, never, R>
function (type parameter) A in <K, A, E>(self: FiberMap<K, A, E>, key: K, options?: {
readonly onlyIfMissing?: boolean | undefined;
readonly propagateInterruption?: boolean | undefined;
readonly startImmediately?: boolean | undefined;
} | undefined): <R, XE extends E, XA extends A>(effect: Effect.Effect<XA, XE, R>) => Effect.Effect<Fiber.Fiber<XA, XE>, never, R>
function (type parameter) E in <K, A, E>(self: FiberMap<K, A, E>, key: K, options?: {
readonly onlyIfMissing?: boolean | undefined;
readonly propagateInterruption?: boolean | undefined;
readonly startImmediately?: boolean | undefined;
} | undefined): <R, XE extends E, XA extends A>(effect: Effect.Effect<XA, XE, R>) => Effect.Effect<Fiber.Fiber<XA, XE>, never, R>
self: FiberMap<K, A, E>(parameter) self: {
deferred: Deferred.Deferred<void, unknown>;
state: { readonly _tag: "Open"; readonly backing: MutableHashMap.MutableHashMap<K, Fiber.Fiber<A, E>> } | { readonly _tag: "Closed" };
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 FiberMap<in out K, out A = unknown, out E = unknown>A FiberMap is a collection of fibers, indexed by a key. When the associated
Scope is closed, all fibers in the map will be interrupted. Fibers are
automatically removed from the map when they complete.
Example (Managing fibers in a map)
import { Effect, FiberMap } from "effect"
// Create a FiberMap with string keys
const program = Effect.gen(function*() {
const map = yield* FiberMap.make<string>()
// Add some fibers to the map
yield* FiberMap.run(map, "task1", Effect.never)
yield* FiberMap.run(map, "task2", Effect.never)
// Get the size of the map
const size = yield* FiberMap.size(map)
console.log(size) // 2
})
FiberMap<function (type parameter) K in <K, A, E>(self: FiberMap<K, A, E>, key: K, options?: {
readonly onlyIfMissing?: boolean | undefined;
readonly propagateInterruption?: boolean | undefined;
readonly startImmediately?: boolean | undefined;
} | undefined): <R, XE extends E, XA extends A>(effect: Effect.Effect<XA, XE, R>) => Effect.Effect<Fiber.Fiber<XA, XE>, never, R>
function (type parameter) A in <K, A, E>(self: FiberMap<K, A, E>, key: K, options?: {
readonly onlyIfMissing?: boolean | undefined;
readonly propagateInterruption?: boolean | undefined;
readonly startImmediately?: boolean | undefined;
} | undefined): <R, XE extends E, XA extends A>(effect: Effect.Effect<XA, XE, R>) => Effect.Effect<Fiber.Fiber<XA, XE>, never, R>
function (type parameter) E in <K, A, E>(self: FiberMap<K, A, E>, key: K, options?: {
readonly onlyIfMissing?: boolean | undefined;
readonly propagateInterruption?: boolean | undefined;
readonly startImmediately?: boolean | undefined;
} | undefined): <R, XE extends E, XA extends A>(effect: Effect.Effect<XA, XE, R>) => Effect.Effect<Fiber.Fiber<XA, XE>, never, R>
key: Kkey: function (type parameter) K in <K, A, E>(self: FiberMap<K, A, E>, key: K, options?: {
readonly onlyIfMissing?: boolean | undefined;
readonly propagateInterruption?: boolean | undefined;
readonly startImmediately?: boolean | undefined;
} | undefined): <R, XE extends E, XA extends A>(effect: Effect.Effect<XA, XE, R>) => Effect.Effect<Fiber.Fiber<XA, XE>, never, R>
options: | {
readonly onlyIfMissing?: boolean | undefined
readonly propagateInterruption?:
| boolean
| undefined
readonly startImmediately?:
| boolean
| undefined
}
| undefined
onlyIfMissing?: boolean | undefinedonlyIfMissing?: boolean | undefined
readonly propagateInterruption?: boolean | undefinedpropagateInterruption?: boolean | undefined
readonly startImmediately?: boolean | undefinedstartImmediately?: boolean | undefined
} | undefined
): <function (type parameter) R in <R, XE extends E, XA extends A>(effect: Effect.Effect<XA, XE, R>): Effect.Effect<Fiber.Fiber<XA, XE>, never, R>R, function (type parameter) XE in <R, XE extends E, XA extends A>(effect: Effect.Effect<XA, XE, R>): Effect.Effect<Fiber.Fiber<XA, XE>, never, R>XE extends function (type parameter) E in <K, A, E>(self: FiberMap<K, A, E>, key: K, options?: {
readonly onlyIfMissing?: boolean | undefined;
readonly propagateInterruption?: boolean | undefined;
readonly startImmediately?: boolean | undefined;
} | undefined): <R, XE extends E, XA extends A>(effect: Effect.Effect<XA, XE, R>) => Effect.Effect<Fiber.Fiber<XA, XE>, never, R>
function (type parameter) XA in <R, XE extends E, XA extends A>(effect: Effect.Effect<XA, XE, R>): Effect.Effect<Fiber.Fiber<XA, XE>, never, R>XA extends function (type parameter) A in <K, A, E>(self: FiberMap<K, A, E>, key: K, options?: {
readonly onlyIfMissing?: boolean | undefined;
readonly propagateInterruption?: boolean | undefined;
readonly startImmediately?: boolean | undefined;
} | undefined): <R, XE extends E, XA extends A>(effect: Effect.Effect<XA, XE, R>) => Effect.Effect<Fiber.Fiber<XA, XE>, never, R>
effect: Effect.Effect<XA, XE, R>(parameter) effect: {
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.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) XA in <R, XE extends E, XA extends A>(effect: Effect.Effect<XA, XE, R>): Effect.Effect<Fiber.Fiber<XA, XE>, never, R>XA, function (type parameter) XE in <R, XE extends E, XA extends A>(effect: Effect.Effect<XA, XE, R>): Effect.Effect<Fiber.Fiber<XA, XE>, never, R>XE, function (type parameter) R in <R, XE extends E, XA extends A>(effect: Effect.Effect<XA, XE, R>): Effect.Effect<Fiber.Fiber<XA, XE>, never, R>R>
) => import EffectEffect.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<import FiberFiber.interface Fiber<out A, out E = never>A runtime fiber is a lightweight thread that executes Effects. Fibers are
the unit of concurrency in Effect. They provide a way to run multiple
Effects concurrently while maintaining structured concurrency and
cancellation safety.
When to use
Use to observe, join, interrupt, or coordinate work that has already been
forked.
Details
A fiber exposes both safe Effect-based operations, such as
await
,
join
, and
interrupt
, and low-level runtime fields used by
the scheduler and runtime internals.
Gotchas
Prefer the exported functions in this module over calling interruptUnsafe
or pollUnsafe directly. The unsafe methods are immediate runtime hooks and
do not provide the same Effect-based sequencing guarantees.
Example (Awaiting a forked fiber)
import { Effect, Fiber } from "effect"
const program = Effect.gen(function*() {
// Fork an effect to run in a new fiber
const fiber = yield* Effect.forkChild(Effect.succeed(42))
// Wait for the fiber to complete and get its result
const result = yield* Fiber.await(fiber)
console.log(result) // Exit.succeed(42)
return result
})
The Fiber namespace contains utility types and functions for working with fibers.
It provides type-level utilities for fiber operations and variance encoding.
When to use
Use to reference type-level helpers associated with Fiber.
Details
The namespace currently exposes type-level support used by the Fiber
interface. Runtime operations are exported as module-level functions.
Example (Working with fiber types)
import { Effect, Fiber } from "effect"
const program = Effect.gen(function*() {
// Create a fiber
const fiber = yield* Effect.forkChild(Effect.succeed(42))
// Use namespace types for variance
const typedFiber: Fiber.Fiber<number, never> = fiber
// Access fiber properties
console.log(`Fiber ID: ${fiber.id}`)
// Join the fiber
const result = yield* Fiber.join(fiber)
return result // 42
})
Fiber<function (type parameter) XA in <R, XE extends E, XA extends A>(effect: Effect.Effect<XA, XE, R>): Effect.Effect<Fiber.Fiber<XA, XE>, never, R>XA, function (type parameter) XE in <R, XE extends E, XA extends A>(effect: Effect.Effect<XA, XE, R>): Effect.Effect<Fiber.Fiber<XA, XE>, never, R>XE>, never, function (type parameter) R in <R, XE extends E, XA extends A>(effect: Effect.Effect<XA, XE, R>): Effect.Effect<Fiber.Fiber<XA, XE>, never, R>R>
<function (type parameter) K in <K, A, E, R, XE extends E, XA extends A>(self: FiberMap<K, A, E>, key: K, effect: Effect.Effect<XA, XE, R>, options?: {
readonly onlyIfMissing?: boolean | undefined;
readonly propagateInterruption?: boolean | undefined;
readonly startImmediately?: boolean | undefined;
} | undefined): Effect.Effect<Fiber.Fiber<XA, XE>, never, R>
function (type parameter) A in <K, A, E, R, XE extends E, XA extends A>(self: FiberMap<K, A, E>, key: K, effect: Effect.Effect<XA, XE, R>, options?: {
readonly onlyIfMissing?: boolean | undefined;
readonly propagateInterruption?: boolean | undefined;
readonly startImmediately?: boolean | undefined;
} | undefined): Effect.Effect<Fiber.Fiber<XA, XE>, never, R>
function (type parameter) E in <K, A, E, R, XE extends E, XA extends A>(self: FiberMap<K, A, E>, key: K, effect: Effect.Effect<XA, XE, R>, options?: {
readonly onlyIfMissing?: boolean | undefined;
readonly propagateInterruption?: boolean | undefined;
readonly startImmediately?: boolean | undefined;
} | undefined): Effect.Effect<Fiber.Fiber<XA, XE>, never, R>
function (type parameter) R in <K, A, E, R, XE extends E, XA extends A>(self: FiberMap<K, A, E>, key: K, effect: Effect.Effect<XA, XE, R>, options?: {
readonly onlyIfMissing?: boolean | undefined;
readonly propagateInterruption?: boolean | undefined;
readonly startImmediately?: boolean | undefined;
} | undefined): Effect.Effect<Fiber.Fiber<XA, XE>, never, R>
function (type parameter) XE in <K, A, E, R, XE extends E, XA extends A>(self: FiberMap<K, A, E>, key: K, effect: Effect.Effect<XA, XE, R>, options?: {
readonly onlyIfMissing?: boolean | undefined;
readonly propagateInterruption?: boolean | undefined;
readonly startImmediately?: boolean | undefined;
} | undefined): Effect.Effect<Fiber.Fiber<XA, XE>, never, R>
function (type parameter) E in <K, A, E, R, XE extends E, XA extends A>(self: FiberMap<K, A, E>, key: K, effect: Effect.Effect<XA, XE, R>, options?: {
readonly onlyIfMissing?: boolean | undefined;
readonly propagateInterruption?: boolean | undefined;
readonly startImmediately?: boolean | undefined;
} | undefined): Effect.Effect<Fiber.Fiber<XA, XE>, never, R>
function (type parameter) XA in <K, A, E, R, XE extends E, XA extends A>(self: FiberMap<K, A, E>, key: K, effect: Effect.Effect<XA, XE, R>, options?: {
readonly onlyIfMissing?: boolean | undefined;
readonly propagateInterruption?: boolean | undefined;
readonly startImmediately?: boolean | undefined;
} | undefined): Effect.Effect<Fiber.Fiber<XA, XE>, never, R>
function (type parameter) A in <K, A, E, R, XE extends E, XA extends A>(self: FiberMap<K, A, E>, key: K, effect: Effect.Effect<XA, XE, R>, options?: {
readonly onlyIfMissing?: boolean | undefined;
readonly propagateInterruption?: boolean | undefined;
readonly startImmediately?: boolean | undefined;
} | undefined): Effect.Effect<Fiber.Fiber<XA, XE>, never, R>
self: FiberMap<K, A, E>(parameter) self: {
deferred: Deferred.Deferred<void, unknown>;
state: { readonly _tag: "Open"; readonly backing: MutableHashMap.MutableHashMap<K, Fiber.Fiber<A, E>> } | { readonly _tag: "Closed" };
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 FiberMap<in out K, out A = unknown, out E = unknown>A FiberMap is a collection of fibers, indexed by a key. When the associated
Scope is closed, all fibers in the map will be interrupted. Fibers are
automatically removed from the map when they complete.
Example (Managing fibers in a map)
import { Effect, FiberMap } from "effect"
// Create a FiberMap with string keys
const program = Effect.gen(function*() {
const map = yield* FiberMap.make<string>()
// Add some fibers to the map
yield* FiberMap.run(map, "task1", Effect.never)
yield* FiberMap.run(map, "task2", Effect.never)
// Get the size of the map
const size = yield* FiberMap.size(map)
console.log(size) // 2
})
FiberMap<function (type parameter) K in <K, A, E, R, XE extends E, XA extends A>(self: FiberMap<K, A, E>, key: K, effect: Effect.Effect<XA, XE, R>, options?: {
readonly onlyIfMissing?: boolean | undefined;
readonly propagateInterruption?: boolean | undefined;
readonly startImmediately?: boolean | undefined;
} | undefined): Effect.Effect<Fiber.Fiber<XA, XE>, never, R>
function (type parameter) A in <K, A, E, R, XE extends E, XA extends A>(self: FiberMap<K, A, E>, key: K, effect: Effect.Effect<XA, XE, R>, options?: {
readonly onlyIfMissing?: boolean | undefined;
readonly propagateInterruption?: boolean | undefined;
readonly startImmediately?: boolean | undefined;
} | undefined): Effect.Effect<Fiber.Fiber<XA, XE>, never, R>
function (type parameter) E in <K, A, E, R, XE extends E, XA extends A>(self: FiberMap<K, A, E>, key: K, effect: Effect.Effect<XA, XE, R>, options?: {
readonly onlyIfMissing?: boolean | undefined;
readonly propagateInterruption?: boolean | undefined;
readonly startImmediately?: boolean | undefined;
} | undefined): Effect.Effect<Fiber.Fiber<XA, XE>, never, R>
key: Kkey: function (type parameter) K in <K, A, E, R, XE extends E, XA extends A>(self: FiberMap<K, A, E>, key: K, effect: Effect.Effect<XA, XE, R>, options?: {
readonly onlyIfMissing?: boolean | undefined;
readonly propagateInterruption?: boolean | undefined;
readonly startImmediately?: boolean | undefined;
} | undefined): Effect.Effect<Fiber.Fiber<XA, XE>, never, R>
effect: Effect.Effect<XA, XE, R>(parameter) effect: {
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.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) XA in <K, A, E, R, XE extends E, XA extends A>(self: FiberMap<K, A, E>, key: K, effect: Effect.Effect<XA, XE, R>, options?: {
readonly onlyIfMissing?: boolean | undefined;
readonly propagateInterruption?: boolean | undefined;
readonly startImmediately?: boolean | undefined;
} | undefined): Effect.Effect<Fiber.Fiber<XA, XE>, never, R>
function (type parameter) XE in <K, A, E, R, XE extends E, XA extends A>(self: FiberMap<K, A, E>, key: K, effect: Effect.Effect<XA, XE, R>, options?: {
readonly onlyIfMissing?: boolean | undefined;
readonly propagateInterruption?: boolean | undefined;
readonly startImmediately?: boolean | undefined;
} | undefined): Effect.Effect<Fiber.Fiber<XA, XE>, never, R>
function (type parameter) R in <K, A, E, R, XE extends E, XA extends A>(self: FiberMap<K, A, E>, key: K, effect: Effect.Effect<XA, XE, R>, options?: {
readonly onlyIfMissing?: boolean | undefined;
readonly propagateInterruption?: boolean | undefined;
readonly startImmediately?: boolean | undefined;
} | undefined): Effect.Effect<Fiber.Fiber<XA, XE>, never, R>
options: | {
readonly onlyIfMissing?: boolean | undefined
readonly propagateInterruption?:
| boolean
| undefined
readonly startImmediately?:
| boolean
| undefined
}
| undefined
onlyIfMissing?: boolean | undefinedonlyIfMissing?: boolean | undefined
readonly propagateInterruption?: boolean | undefinedpropagateInterruption?: boolean | undefined
readonly startImmediately?: boolean | undefinedstartImmediately?: boolean | undefined
} | undefined
): import EffectEffect.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<import FiberFiber.interface Fiber<out A, out E = never>A runtime fiber is a lightweight thread that executes Effects. Fibers are
the unit of concurrency in Effect. They provide a way to run multiple
Effects concurrently while maintaining structured concurrency and
cancellation safety.
When to use
Use to observe, join, interrupt, or coordinate work that has already been
forked.
Details
A fiber exposes both safe Effect-based operations, such as
await
,
join
, and
interrupt
, and low-level runtime fields used by
the scheduler and runtime internals.
Gotchas
Prefer the exported functions in this module over calling interruptUnsafe
or pollUnsafe directly. The unsafe methods are immediate runtime hooks and
do not provide the same Effect-based sequencing guarantees.
Example (Awaiting a forked fiber)
import { Effect, Fiber } from "effect"
const program = Effect.gen(function*() {
// Fork an effect to run in a new fiber
const fiber = yield* Effect.forkChild(Effect.succeed(42))
// Wait for the fiber to complete and get its result
const result = yield* Fiber.await(fiber)
console.log(result) // Exit.succeed(42)
return result
})
The Fiber namespace contains utility types and functions for working with fibers.
It provides type-level utilities for fiber operations and variance encoding.
When to use
Use to reference type-level helpers associated with Fiber.
Details
The namespace currently exposes type-level support used by the Fiber
interface. Runtime operations are exported as module-level functions.
Example (Working with fiber types)
import { Effect, Fiber } from "effect"
const program = Effect.gen(function*() {
// Create a fiber
const fiber = yield* Effect.forkChild(Effect.succeed(42))
// Use namespace types for variance
const typedFiber: Fiber.Fiber<number, never> = fiber
// Access fiber properties
console.log(`Fiber ID: ${fiber.id}`)
// Join the fiber
const result = yield* Fiber.join(fiber)
return result // 42
})
Fiber<function (type parameter) XA in <K, A, E, R, XE extends E, XA extends A>(self: FiberMap<K, A, E>, key: K, effect: Effect.Effect<XA, XE, R>, options?: {
readonly onlyIfMissing?: boolean | undefined;
readonly propagateInterruption?: boolean | undefined;
readonly startImmediately?: boolean | undefined;
} | undefined): Effect.Effect<Fiber.Fiber<XA, XE>, never, R>
function (type parameter) XE in <K, A, E, R, XE extends E, XA extends A>(self: FiberMap<K, A, E>, key: K, effect: Effect.Effect<XA, XE, R>, options?: {
readonly onlyIfMissing?: boolean | undefined;
readonly propagateInterruption?: boolean | undefined;
readonly startImmediately?: boolean | undefined;
} | undefined): Effect.Effect<Fiber.Fiber<XA, XE>, never, R>
function (type parameter) R in <K, A, E, R, XE extends E, XA extends A>(self: FiberMap<K, A, E>, key: K, effect: Effect.Effect<XA, XE, R>, options?: {
readonly onlyIfMissing?: boolean | undefined;
readonly propagateInterruption?: boolean | undefined;
readonly startImmediately?: boolean | undefined;
} | undefined): Effect.Effect<Fiber.Fiber<XA, XE>, never, R>
const self: anyself = function (local var) arguments: IArgumentsarguments[0]
if (import EffectEffect.const isEffect: (
u: unknown
) => u is Effect<any, any, any>
Checks whether a value is an Effect.
Example (Checking whether a value is an Effect)
import { Effect } from "effect"
console.log(Effect.isEffect(Effect.succeed(1))) // true
console.log(Effect.isEffect("hello")) // false
isEffect(function (local var) arguments: IArgumentsarguments[2])) {
return const runImpl: <
K,
A,
E,
R,
XE extends E,
XA extends A
>(
self: FiberMap<K, A, E>,
key: K,
effect: Effect.Effect<XA, XE, R>,
options?: {
readonly onlyIfMissing?: boolean
readonly propagateInterruption?:
| boolean
| undefined
}
) => Effect.Effect<
Fiber.Fiber<XA, XE>,
never,
never
>
const self: anyself, function (local var) arguments: IArgumentsarguments[1], function (local var) arguments: IArgumentsarguments[2], function (local var) arguments: IArgumentsarguments[3]) as any
}
const const key: anykey = function (local var) arguments: IArgumentsarguments[1]
const const options: anyoptions = function (local var) arguments: IArgumentsarguments[2]
return (effect: Effect.Effect<any, any, any>(parameter) effect: {
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.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<any, any, any>) => const runImpl: <
K,
A,
E,
R,
XE extends E,
XA extends A
>(
self: FiberMap<K, A, E>,
key: K,
effect: Effect.Effect<XA, XE, R>,
options?: {
readonly onlyIfMissing?: boolean
readonly propagateInterruption?:
| boolean
| undefined
}
) => Effect.Effect<
Fiber.Fiber<XA, XE>,
never,
never
>
const self: anyself, const key: anykey, effect: Effect.Effect<any, any, any>(parameter) effect: {
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 options: anyoptions)
}