(
options:
| { readonly capacity: "unbounded" }
| {
readonly capacity: number
readonly strategy?: "dropping" | "sliding" | "suspend" | undefined
}
): <OutElem, OutErr, OutDone, Env>(
self: Channel<OutElem, OutErr, OutDone, unknown, unknown, unknown, Env>
) => Effect.Effect<
Queue.Dequeue<OutElem, OutErr | Cause.Done>,
never,
Env | Scope.Scope
>
<OutElem, OutErr, OutDone, Env>(
self: Channel<OutElem, OutErr, OutDone, unknown, unknown, unknown, Env>,
options:
| { readonly capacity: "unbounded" }
| {
readonly capacity: number
readonly strategy?: "dropping" | "sliding" | "suspend" | undefined
}
): Effect.Effect<
Queue.Dequeue<OutElem, OutErr | Cause.Done>,
never,
Env | Scope.Scope
>Creates a scoped queue and forks the channel to feed it for concurrent consumption.
Details
Output elements are offered to the queue. Channel completion and failure are signaled through the queue. The queue is shut down when the surrounding scope closes.
Example (Converting channels to queues)
import { Channel, Data } from "effect"
class QueueError extends Data.TaggedError("QueueError")<{
readonly operation: string
}> {}
// Create a channel with data
const dataChannel = Channel.fromIterable([1, 2, 3, 4, 5])
// Convert to queue for concurrent processing
const queueEffect = Channel.toQueue(dataChannel, { capacity: 32 })
// The queue can be used for concurrent consumption
// Multiple consumers can read from the queuedestructors
Source effect/Channel.ts:822441 lines
export const const toQueue: {
(
options:
| { readonly capacity: "unbounded" }
| {
readonly capacity: number
readonly strategy?:
| "dropping"
| "sliding"
| "suspend"
| undefined
}
): <OutElem, OutErr, OutDone, Env>(
self: Channel<
OutElem,
OutErr,
OutDone,
unknown,
unknown,
unknown,
Env
>
) => Effect.Effect<
Queue.Dequeue<OutElem, OutErr | Cause.Done>,
never,
Env | Scope.Scope
>
<OutElem, OutErr, OutDone, Env>(
self: Channel<
OutElem,
OutErr,
OutDone,
unknown,
unknown,
unknown,
Env
>,
options:
| { readonly capacity: "unbounded" }
| {
readonly capacity: number
readonly strategy?:
| "dropping"
| "sliding"
| "suspend"
| undefined
}
): Effect.Effect<
Queue.Dequeue<OutElem, OutErr | Cause.Done>,
never,
Env | Scope.Scope
>
}
Creates a scoped queue and forks the channel to feed it for concurrent
consumption.
Details
Output elements are offered to the queue. Channel completion and failure are
signaled through the queue. The queue is shut down when the surrounding scope
closes.
Example (Converting channels to queues)
import { Channel, Data } from "effect"
class QueueError extends Data.TaggedError("QueueError")<{
readonly operation: string
}> {}
// Create a channel with data
const dataChannel = Channel.fromIterable([1, 2, 3, 4, 5])
// Convert to queue for concurrent processing
const queueEffect = Channel.toQueue(dataChannel, { capacity: 32 })
// The queue can be used for concurrent consumption
// Multiple consumers can read from the queue
toQueue: {
(
options: | {
readonly capacity: "unbounded"
}
| {
readonly capacity: number
readonly strategy?:
| "dropping"
| "sliding"
| "suspend"
| undefined
}
capacity: "unbounded"capacity: "unbounded"
} | {
readonly capacity: numbercapacity: number
readonly strategy?: | "sliding"
| "dropping"
| "suspend"
| undefined
function (type parameter) OutElem in <OutElem, OutErr, OutDone, Env>(self: Channel<OutElem, OutErr, OutDone, unknown, unknown, unknown, Env>): Effect.Effect<Queue.Dequeue<OutElem, OutErr | Cause.Done>, never, Env | Scope.Scope>OutElem, function (type parameter) OutErr in <OutElem, OutErr, OutDone, Env>(self: Channel<OutElem, OutErr, OutDone, unknown, unknown, unknown, Env>): Effect.Effect<Queue.Dequeue<OutElem, OutErr | Cause.Done>, never, Env | Scope.Scope>OutErr, function (type parameter) OutDone in <OutElem, OutErr, OutDone, Env>(self: Channel<OutElem, OutErr, OutDone, unknown, unknown, unknown, Env>): Effect.Effect<Queue.Dequeue<OutElem, OutErr | Cause.Done>, never, Env | Scope.Scope>OutDone, function (type parameter) Env in <OutElem, OutErr, OutDone, Env>(self: Channel<OutElem, OutErr, OutDone, unknown, unknown, unknown, Env>): Effect.Effect<Queue.Dequeue<OutElem, OutErr | Cause.Done>, never, Env | Scope.Scope>Env>(
self: Channel<
OutElem,
OutErr,
OutDone,
unknown,
unknown,
unknown,
Env
>
(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; <…;
}
interface Channel<out OutElem, out OutErr = never, out OutDone = void, in InElem = unknown, in InErr = unknown, in InDone = unknown, out Env = never>A Channel is a nexus of I/O operations, which supports both reading and
writing. A channel may read values of type InElem and write values of type
OutElem. When the channel finishes, it yields a value of type OutDone. A
channel may fail with a value of type OutErr.
Details
Channels are the foundation of Streams: both streams and sinks are built on
channels. Most users shouldn't have to use channels directly, as streams and
sinks are much more convenient and cover all common use cases. However, when
adding new stream and sink operators, or doing something highly specialized,
it may be useful to use channels directly.
Channels compose in a variety of ways:
- Piping: One channel can be piped to another channel, assuming the
input type of the second is the same as the output type of the first.
- Sequencing: The terminal value of one channel can be used to create
another channel, and both the first channel and the function that makes
the second channel can be composed into a channel.
- Concatenating: The output of one channel can be used to create other
channels, which are all concatenated together. The first channel and the
function that makes the other channels can be composed into a channel.
Example (Typing channels)
import type { Channel } from "effect"
// A channel that outputs numbers and requires no environment
type NumberChannel = Channel.Channel<number>
// A channel that outputs strings, can fail with Error, completes with boolean
type StringChannel = Channel.Channel<string, Error, boolean>
// A channel with all type parameters specified
type FullChannel = Channel.Channel<
string, // OutElem - output elements
Error, // OutErr - output errors
number, // OutDone - completion value
number, // InElem - input elements
string, // InErr - input errors
boolean, // InDone - input completion
{ db: string } // Env - required environment
>
Channel<function (type parameter) OutElem in <OutElem, OutErr, OutDone, Env>(self: Channel<OutElem, OutErr, OutDone, unknown, unknown, unknown, Env>): Effect.Effect<Queue.Dequeue<OutElem, OutErr | Cause.Done>, never, Env | Scope.Scope>OutElem, function (type parameter) OutErr in <OutElem, OutErr, OutDone, Env>(self: Channel<OutElem, OutErr, OutDone, unknown, unknown, unknown, Env>): Effect.Effect<Queue.Dequeue<OutElem, OutErr | Cause.Done>, never, Env | Scope.Scope>OutErr, function (type parameter) OutDone in <OutElem, OutErr, OutDone, Env>(self: Channel<OutElem, OutErr, OutDone, unknown, unknown, unknown, Env>): Effect.Effect<Queue.Dequeue<OutElem, OutErr | Cause.Done>, never, Env | Scope.Scope>OutDone, unknown, unknown, unknown, function (type parameter) Env in <OutElem, OutErr, OutDone, Env>(self: Channel<OutElem, OutErr, OutDone, unknown, unknown, unknown, Env>): Effect.Effect<Queue.Dequeue<OutElem, OutErr | Cause.Done>, never, Env | Scope.Scope>Env>
) => 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 QueueQueue.interface Dequeue<out A, out E = never>A Dequeue is a queue that can be taken from.
Details
This interface represents the read-only part of a Queue, allowing you to take
elements from the queue but not offer elements to it.
Example (Taking through dequeue handles)
import { Effect, Queue } from "effect"
const program = Effect.gen(function*() {
const queue = yield* Queue.bounded<string, never>(10)
// A Dequeue can only take elements
const dequeue: Queue.Dequeue<string> = queue
// Pre-populate the queue
yield* Queue.offerAll(queue, ["a", "b", "c"])
// Take elements using dequeue interface
const item = yield* Queue.take(dequeue)
console.log(item) // "a"
})
Companion namespace containing type-level metadata for the Dequeue
read-only queue interface.
Dequeue<function (type parameter) OutElem in <OutElem, OutErr, OutDone, Env>(self: Channel<OutElem, OutErr, OutDone, unknown, unknown, unknown, Env>): Effect.Effect<Queue.Dequeue<OutElem, OutErr | Cause.Done>, never, Env | Scope.Scope>OutElem, function (type parameter) OutErr in <OutElem, OutErr, OutDone, Env>(self: Channel<OutElem, OutErr, OutDone, unknown, unknown, unknown, Env>): Effect.Effect<Queue.Dequeue<OutElem, OutErr | Cause.Done>, never, Env | Scope.Scope>OutErr | import CauseCause.type Cause.Done = /*unresolved*/ anyDone>, never, function (type parameter) Env in <OutElem, OutErr, OutDone, Env>(self: Channel<OutElem, OutErr, OutDone, unknown, unknown, unknown, Env>): Effect.Effect<Queue.Dequeue<OutElem, OutErr | Cause.Done>, never, Env | Scope.Scope>Env | import ScopeScope.Scope>
<function (type parameter) OutElem in <OutElem, OutErr, OutDone, Env>(self: Channel<OutElem, OutErr, OutDone, unknown, unknown, unknown, Env>, options: {
readonly capacity: "unbounded";
} | {
readonly capacity: number;
readonly strategy?: "dropping" | "sliding" | "suspend" | undefined;
}): Effect.Effect<Queue.Dequeue<OutElem, OutErr | Cause.Done>, never, Env | Scope.Scope>
function (type parameter) OutErr in <OutElem, OutErr, OutDone, Env>(self: Channel<OutElem, OutErr, OutDone, unknown, unknown, unknown, Env>, options: {
readonly capacity: "unbounded";
} | {
readonly capacity: number;
readonly strategy?: "dropping" | "sliding" | "suspend" | undefined;
}): Effect.Effect<Queue.Dequeue<OutElem, OutErr | Cause.Done>, never, Env | Scope.Scope>
function (type parameter) OutDone in <OutElem, OutErr, OutDone, Env>(self: Channel<OutElem, OutErr, OutDone, unknown, unknown, unknown, Env>, options: {
readonly capacity: "unbounded";
} | {
readonly capacity: number;
readonly strategy?: "dropping" | "sliding" | "suspend" | undefined;
}): Effect.Effect<Queue.Dequeue<OutElem, OutErr | Cause.Done>, never, Env | Scope.Scope>
function (type parameter) Env in <OutElem, OutErr, OutDone, Env>(self: Channel<OutElem, OutErr, OutDone, unknown, unknown, unknown, Env>, options: {
readonly capacity: "unbounded";
} | {
readonly capacity: number;
readonly strategy?: "dropping" | "sliding" | "suspend" | undefined;
}): Effect.Effect<Queue.Dequeue<OutElem, OutErr | Cause.Done>, never, Env | Scope.Scope>
self: Channel<
OutElem,
OutErr,
OutDone,
unknown,
unknown,
unknown,
Env
>
(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; <…;
}
interface Channel<out OutElem, out OutErr = never, out OutDone = void, in InElem = unknown, in InErr = unknown, in InDone = unknown, out Env = never>A Channel is a nexus of I/O operations, which supports both reading and
writing. A channel may read values of type InElem and write values of type
OutElem. When the channel finishes, it yields a value of type OutDone. A
channel may fail with a value of type OutErr.
Details
Channels are the foundation of Streams: both streams and sinks are built on
channels. Most users shouldn't have to use channels directly, as streams and
sinks are much more convenient and cover all common use cases. However, when
adding new stream and sink operators, or doing something highly specialized,
it may be useful to use channels directly.
Channels compose in a variety of ways:
- Piping: One channel can be piped to another channel, assuming the
input type of the second is the same as the output type of the first.
- Sequencing: The terminal value of one channel can be used to create
another channel, and both the first channel and the function that makes
the second channel can be composed into a channel.
- Concatenating: The output of one channel can be used to create other
channels, which are all concatenated together. The first channel and the
function that makes the other channels can be composed into a channel.
Example (Typing channels)
import type { Channel } from "effect"
// A channel that outputs numbers and requires no environment
type NumberChannel = Channel.Channel<number>
// A channel that outputs strings, can fail with Error, completes with boolean
type StringChannel = Channel.Channel<string, Error, boolean>
// A channel with all type parameters specified
type FullChannel = Channel.Channel<
string, // OutElem - output elements
Error, // OutErr - output errors
number, // OutDone - completion value
number, // InElem - input elements
string, // InErr - input errors
boolean, // InDone - input completion
{ db: string } // Env - required environment
>
Channel<function (type parameter) OutElem in <OutElem, OutErr, OutDone, Env>(self: Channel<OutElem, OutErr, OutDone, unknown, unknown, unknown, Env>, options: {
readonly capacity: "unbounded";
} | {
readonly capacity: number;
readonly strategy?: "dropping" | "sliding" | "suspend" | undefined;
}): Effect.Effect<Queue.Dequeue<OutElem, OutErr | Cause.Done>, never, Env | Scope.Scope>
function (type parameter) OutErr in <OutElem, OutErr, OutDone, Env>(self: Channel<OutElem, OutErr, OutDone, unknown, unknown, unknown, Env>, options: {
readonly capacity: "unbounded";
} | {
readonly capacity: number;
readonly strategy?: "dropping" | "sliding" | "suspend" | undefined;
}): Effect.Effect<Queue.Dequeue<OutElem, OutErr | Cause.Done>, never, Env | Scope.Scope>
function (type parameter) OutDone in <OutElem, OutErr, OutDone, Env>(self: Channel<OutElem, OutErr, OutDone, unknown, unknown, unknown, Env>, options: {
readonly capacity: "unbounded";
} | {
readonly capacity: number;
readonly strategy?: "dropping" | "sliding" | "suspend" | undefined;
}): Effect.Effect<Queue.Dequeue<OutElem, OutErr | Cause.Done>, never, Env | Scope.Scope>
function (type parameter) Env in <OutElem, OutErr, OutDone, Env>(self: Channel<OutElem, OutErr, OutDone, unknown, unknown, unknown, Env>, options: {
readonly capacity: "unbounded";
} | {
readonly capacity: number;
readonly strategy?: "dropping" | "sliding" | "suspend" | undefined;
}): Effect.Effect<Queue.Dequeue<OutElem, OutErr | Cause.Done>, never, Env | Scope.Scope>
options: | {
readonly capacity: "unbounded"
}
| {
readonly capacity: number
readonly strategy?:
| "dropping"
| "sliding"
| "suspend"
| undefined
}
capacity: "unbounded"capacity: "unbounded"
} | {
readonly capacity: numbercapacity: number
readonly strategy?: | "sliding"
| "dropping"
| "suspend"
| 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 QueueQueue.interface Dequeue<out A, out E = never>A Dequeue is a queue that can be taken from.
Details
This interface represents the read-only part of a Queue, allowing you to take
elements from the queue but not offer elements to it.
Example (Taking through dequeue handles)
import { Effect, Queue } from "effect"
const program = Effect.gen(function*() {
const queue = yield* Queue.bounded<string, never>(10)
// A Dequeue can only take elements
const dequeue: Queue.Dequeue<string> = queue
// Pre-populate the queue
yield* Queue.offerAll(queue, ["a", "b", "c"])
// Take elements using dequeue interface
const item = yield* Queue.take(dequeue)
console.log(item) // "a"
})
Companion namespace containing type-level metadata for the Dequeue
read-only queue interface.
Dequeue<function (type parameter) OutElem in <OutElem, OutErr, OutDone, Env>(self: Channel<OutElem, OutErr, OutDone, unknown, unknown, unknown, Env>, options: {
readonly capacity: "unbounded";
} | {
readonly capacity: number;
readonly strategy?: "dropping" | "sliding" | "suspend" | undefined;
}): Effect.Effect<Queue.Dequeue<OutElem, OutErr | Cause.Done>, never, Env | Scope.Scope>
function (type parameter) OutErr in <OutElem, OutErr, OutDone, Env>(self: Channel<OutElem, OutErr, OutDone, unknown, unknown, unknown, Env>, options: {
readonly capacity: "unbounded";
} | {
readonly capacity: number;
readonly strategy?: "dropping" | "sliding" | "suspend" | undefined;
}): Effect.Effect<Queue.Dequeue<OutElem, OutErr | Cause.Done>, never, Env | Scope.Scope>
import CauseCause.type Cause.Done = /*unresolved*/ anyDone>, never, function (type parameter) Env in <OutElem, OutErr, OutDone, Env>(self: Channel<OutElem, OutErr, OutDone, unknown, unknown, unknown, Env>, options: {
readonly capacity: "unbounded";
} | {
readonly capacity: number;
readonly strategy?: "dropping" | "sliding" | "suspend" | undefined;
}): Effect.Effect<Queue.Dequeue<OutElem, OutErr | Cause.Done>, never, Env | Scope.Scope>
import ScopeScope.Scope>
} = dual<(...args: Array<any>) => any, <OutElem, OutErr, OutDone, Env>(self: Channel<OutElem, OutErr, OutDone, unknown, unknown, unknown, Env>, options: {
readonly capacity: "unbounded";
} | {
readonly capacity: number;
readonly strategy?: "dropping" | "sliding" | "suspend" | undefined;
}) => Effect.Effect<Queue.Queue<OutElem, any>, never, Scope.Scope | Env>>(isDataFirst: (args: IArguments) => boolean, body: <OutElem, OutErr, OutDone, Env>(self: Channel<OutElem, OutErr, OutDone, unknown, unknown, unknown, Env>, options: {
readonly capacity: "unbounded";
} | {
readonly capacity: number;
readonly strategy?: "dropping" | "sliding" | "suspend" | undefined;
}) => Effect.Effect<Queue.Queue<OutElem, any>, never, Scope.Scope | Env>): ((...args: Array<any>) => any) & (<OutElem, OutErr, OutDone, Env>(self: Channel<OutElem, OutErr, OutDone, unknown, unknown, unknown, Env>, options: {
readonly capacity: "unbounded";
} | {
readonly capacity: number;
readonly strategy?: "dropping" | "sliding" | "suspend" | undefined;
}) => Effect.Effect<Queue.Queue<OutElem, any>, never, Scope.Scope | Env>) (+1 overload)
Creates a function that can be called in data-first style or data-last
(pipe-friendly) style.
When to use
Use to expose one implementation through both direct and pipe-friendly
call styles.
Details
Pass either the arity of the uncurried function or a predicate that decides
whether the current call is data-first. Arity is the common case. Use a
predicate when optional arguments make arity ambiguous.
Example (Selecting data-first or data-last style by arity)
import { Function, pipe } from "effect"
const sum = Function.dual<
(that: number) => (self: number) => number,
(self: number, that: number) => number
>(2, (self, that) => self + that)
console.log(sum(2, 3)) // 5
console.log(pipe(2, sum(3))) // 5
Example (Defining overloads with call signatures)
import { Function, pipe } from "effect"
const sum: {
(that: number): (self: number) => number
(self: number, that: number): number
} = Function.dual(2, (self: number, that: number): number => self + that)
console.log(sum(2, 3)) // 5
console.log(pipe(2, sum(3))) // 5
Example (Selecting data-first or data-last style with a predicate)
import { Function, pipe } from "effect"
const sum = Function.dual<
(that: number) => (self: number) => number,
(self: number, that: number) => number
>(
(args) => args.length === 2,
(self, that) => self + that
)
console.log(sum(2, 3)) // 5
console.log(pipe(2, sum(3))) // 5
dual(
(args: IArgumentsargs) => const isChannel: (
u: unknown
) => u is Channel<
unknown,
unknown,
unknown,
unknown,
unknown,
unknown,
unknown
>
Checks whether a value is a Channel.
Example (Checking for channels)
import { Channel } from "effect"
const channel = Channel.succeed(42)
console.log(Channel.isChannel(channel)) // true
console.log(Channel.isChannel("not a channel")) // false
isChannel(args: IArgumentsargs[0]),
import EffectEffect.const fnUntraced: <Effect.Effect<void, never, never> | Effect.Effect<Scope.Scope, never, Scope.Scope> | Effect.Effect<Fiber.Fiber<void, never>, never, Env>, Queue.Queue<OutElem, any>, [self: Channel<OutElem, OutErr, OutDone, unknown, unknown, unknown, Env>, options: {
readonly capacity: "unbounded";
} | {
readonly capacity: number;
readonly strategy?: "dropping" | "sliding" | "suspend" | undefined;
}]>(body: (this: Types.unassigned, self: Channel<OutElem, OutErr, OutDone, unknown, unknown, unknown, Env>, options: {
readonly capacity: "unbounded";
} | {
readonly capacity: number;
readonly strategy?: "dropping" | "sliding" | "suspend" | undefined;
}) => Generator<...>) => <OutElem, OutErr, OutDone, Env>(self: Channel<...>, options: {
readonly capacity: "unbounded";
} | {
readonly capacity: number;
readonly strategy?: "dropping" | "sliding" | "suspend" | undefined;
}) => Effect.Effect<...> (+41 overloads)
function (type parameter) OutElem in <OutElem, OutErr, OutDone, Env>(self: Channel<OutElem, OutErr, OutDone, unknown, unknown, unknown, Env>, options: {
readonly capacity: "unbounded";
} | {
readonly capacity: number;
readonly strategy?: "dropping" | "sliding" | "suspend" | undefined;
}): Generator<...>
function (type parameter) OutErr in <OutElem, OutErr, OutDone, Env>(self: Channel<OutElem, OutErr, OutDone, unknown, unknown, unknown, Env>, options: {
readonly capacity: "unbounded";
} | {
readonly capacity: number;
readonly strategy?: "dropping" | "sliding" | "suspend" | undefined;
}): Generator<...>
function (type parameter) OutDone in <OutElem, OutErr, OutDone, Env>(self: Channel<OutElem, OutErr, OutDone, unknown, unknown, unknown, Env>, options: {
readonly capacity: "unbounded";
} | {
readonly capacity: number;
readonly strategy?: "dropping" | "sliding" | "suspend" | undefined;
}): Generator<...>
function (type parameter) Env in <OutElem, OutErr, OutDone, Env>(self: Channel<OutElem, OutErr, OutDone, unknown, unknown, unknown, Env>, options: {
readonly capacity: "unbounded";
} | {
readonly capacity: number;
readonly strategy?: "dropping" | "sliding" | "suspend" | undefined;
}): Generator<...>
self: Channel<
OutElem,
OutErr,
OutDone,
unknown,
unknown,
unknown,
Env
>
(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; <…;
}
interface Channel<out OutElem, out OutErr = never, out OutDone = void, in InElem = unknown, in InErr = unknown, in InDone = unknown, out Env = never>A Channel is a nexus of I/O operations, which supports both reading and
writing. A channel may read values of type InElem and write values of type
OutElem. When the channel finishes, it yields a value of type OutDone. A
channel may fail with a value of type OutErr.
Details
Channels are the foundation of Streams: both streams and sinks are built on
channels. Most users shouldn't have to use channels directly, as streams and
sinks are much more convenient and cover all common use cases. However, when
adding new stream and sink operators, or doing something highly specialized,
it may be useful to use channels directly.
Channels compose in a variety of ways:
- Piping: One channel can be piped to another channel, assuming the
input type of the second is the same as the output type of the first.
- Sequencing: The terminal value of one channel can be used to create
another channel, and both the first channel and the function that makes
the second channel can be composed into a channel.
- Concatenating: The output of one channel can be used to create other
channels, which are all concatenated together. The first channel and the
function that makes the other channels can be composed into a channel.
Example (Typing channels)
import type { Channel } from "effect"
// A channel that outputs numbers and requires no environment
type NumberChannel = Channel.Channel<number>
// A channel that outputs strings, can fail with Error, completes with boolean
type StringChannel = Channel.Channel<string, Error, boolean>
// A channel with all type parameters specified
type FullChannel = Channel.Channel<
string, // OutElem - output elements
Error, // OutErr - output errors
number, // OutDone - completion value
number, // InElem - input elements
string, // InErr - input errors
boolean, // InDone - input completion
{ db: string } // Env - required environment
>
Channel<function (type parameter) OutElem in <OutElem, OutErr, OutDone, Env>(self: Channel<OutElem, OutErr, OutDone, unknown, unknown, unknown, Env>, options: {
readonly capacity: "unbounded";
} | {
readonly capacity: number;
readonly strategy?: "dropping" | "sliding" | "suspend" | undefined;
}): Generator<...>
function (type parameter) OutErr in <OutElem, OutErr, OutDone, Env>(self: Channel<OutElem, OutErr, OutDone, unknown, unknown, unknown, Env>, options: {
readonly capacity: "unbounded";
} | {
readonly capacity: number;
readonly strategy?: "dropping" | "sliding" | "suspend" | undefined;
}): Generator<...>
function (type parameter) OutDone in <OutElem, OutErr, OutDone, Env>(self: Channel<OutElem, OutErr, OutDone, unknown, unknown, unknown, Env>, options: {
readonly capacity: "unbounded";
} | {
readonly capacity: number;
readonly strategy?: "dropping" | "sliding" | "suspend" | undefined;
}): Generator<...>
function (type parameter) Env in <OutElem, OutErr, OutDone, Env>(self: Channel<OutElem, OutErr, OutDone, unknown, unknown, unknown, Env>, options: {
readonly capacity: "unbounded";
} | {
readonly capacity: number;
readonly strategy?: "dropping" | "sliding" | "suspend" | undefined;
}): Generator<...>
options: | {
readonly capacity: "unbounded"
}
| {
readonly capacity: number
readonly strategy?:
| "dropping"
| "sliding"
| "suspend"
| undefined
}
capacity: "unbounded"capacity: "unbounded"
} | {
readonly capacity: numbercapacity: number
readonly strategy?: | "sliding"
| "dropping"
| "suspend"
| undefined
const scope: Scope.Scopeconst scope: {
strategy: "sequential" | "parallel";
state: State.Open | State.Closed | State.Empty;
}
import EffectEffect.const scope: Effect<Scope, never, Scope>const scope: {
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;
}
Returns the current scope for resource management.
Example (Accessing the current scope)
import { Console, Effect } from "effect"
const program = Effect.gen(function*() {
const currentScope = yield* Effect.scope
yield* Console.log("Got scope for resource management")
// Use the scope to manually manage resources if needed
const resource = yield* Effect.acquireRelease(
Console.log("Acquiring resource").pipe(Effect.as("resource")),
() => Console.log("Releasing resource")
)
return resource
})
Effect.runPromise(Effect.scoped(program)).then(console.log)
// Output:
// Got scope for resource management
// Acquiring resource
// resource
// Releasing resource
scope
const const queue: Queue.Queue<
OutElem,
Cause.Done<void> | OutErr
>
const queue: {
strategy: "suspend" | "dropping" | "sliding";
dispatcher: SchedulerDispatcher;
capacity: number;
messages: MutableList.MutableList<any>;
state: Queue.State<any, any>;
scheduleRunning: boolean;
toString: () => string;
toJSON: () => unknown;
}
import QueueQueue.const make: <A, E = never>(
options?:
| {
readonly capacity?: number | undefined
readonly strategy?:
| "suspend"
| "dropping"
| "sliding"
| undefined
}
| undefined
) => Effect<Queue<A, E>>
Creates a Queue with optional capacity and overflow strategy.
Details
By default the queue is unbounded and uses the "suspend" strategy. Provide
capacity for a bounded queue and choose "suspend", "dropping", or
"sliding" to control what happens when the queue is full. The returned
queue can be offered to, taken from, failed, ended, interrupted, or shut down.
Example (Creating queues)
import { Cause, Effect, Queue } from "effect"
Effect.gen(function*() {
const queue = yield* Queue.make<number, string | Cause.Done>()
// add messages to the queue
yield* Queue.offer(queue, 1)
yield* Queue.offer(queue, 2)
yield* Queue.offerAll(queue, [3, 4, 5])
// take messages from the queue
const messages = yield* Queue.takeAll(queue)
console.log(messages) // [1, 2, 3, 4, 5]
// signal that the queue is done
yield* Queue.end(queue)
const done = yield* Effect.flip(Queue.take(queue))
console.log(Cause.isDone(done)) // true
// signal that another queue has failed
const failedQueue = yield* Queue.make<number, string>()
const failed = yield* Queue.fail(failedQueue, "boom")
console.log(failed) // true
})
make<function (type parameter) OutElem in <OutElem, OutErr, OutDone, Env>(self: Channel<OutElem, OutErr, OutDone, unknown, unknown, unknown, Env>, options: {
readonly capacity: "unbounded";
} | {
readonly capacity: number;
readonly strategy?: "dropping" | "sliding" | "suspend" | undefined;
}): Generator<...>
function (type parameter) OutErr in <OutElem, OutErr, OutDone, Env>(self: Channel<OutElem, OutErr, OutDone, unknown, unknown, unknown, Env>, options: {
readonly capacity: "unbounded";
} | {
readonly capacity: number;
readonly strategy?: "dropping" | "sliding" | "suspend" | undefined;
}): Generator<...>
import CauseCause.type Cause.Done = /*unresolved*/ anyDone>({
capacity?: number | undefinedcapacity: typeof options: | {
readonly capacity: "unbounded"
}
| {
readonly capacity: number
readonly strategy?:
| "dropping"
| "sliding"
| "suspend"
| undefined
}
capacity: number | "unbounded"capacity === "number" ? options: {
readonly capacity: number
readonly strategy?:
| "dropping"
| "sliding"
| "suspend"
| undefined
}
capacity: numbercapacity : var undefinedundefined,
strategy?: | "sliding"
| "dropping"
| "suspend"
| undefined
options: | {
readonly capacity: "unbounded"
}
| {
readonly capacity: number
readonly strategy?:
| "dropping"
| "sliding"
| "suspend"
| undefined
}
capacity: number | "unbounded"capacity === "number" ? options: {
readonly capacity: number
readonly strategy?:
| "dropping"
| "sliding"
| "suspend"
| undefined
}
strategy?: | "sliding"
| "dropping"
| "suspend"
| undefined
var undefinedundefined
})
yield* import ScopeScope.const addFinalizer: (
scope: Scope,
finalizer: Effect<unknown>
) => Effect<void>
Registers a finalizer effect on a scope.
Details
If the scope is open, the finalizer runs when the scope closes, regardless of
whether the scope closes successfully or with an error. If the scope is
already closed, the finalizer runs immediately.
Example (Adding finalizers)
import { Console, Effect, Exit, Scope } from "effect"
const program = Effect.gen(function*() {
const scope = yield* Scope.make()
// Add simple finalizers
yield* Scope.addFinalizer(scope, Console.log("Cleanup task 1"))
yield* Scope.addFinalizer(scope, Console.log("Cleanup task 2"))
yield* Scope.addFinalizer(scope, Effect.log("Cleanup task 3"))
// Do some work
yield* Console.log("Doing work...")
// Close the scope
yield* Scope.close(scope, Exit.void)
})
addFinalizer(const scope: Scope.Scopeconst scope: {
strategy: "sequential" | "parallel";
state: State.Open | State.Closed | State.Empty;
}
import QueueQueue.const shutdown: <A, E>(
self: Enqueue<A, E>
) => Effect<boolean>
Shuts down the queue immediately, discarding buffered messages and resuming
pending operations.
Details
The operation is idempotent and returns true, including when the queue has
already been shut down or completed.
Example (Shutting down queues)
import { Effect, Queue } from "effect"
const program = Effect.gen(function*() {
const queue = yield* Queue.bounded<number>(2)
// Add messages
yield* Queue.offer(queue, 1)
yield* Queue.offer(queue, 2)
// Shutdown clears buffered messages and prevents further offers
const wasShutdown = yield* Queue.shutdown(queue)
console.log(wasShutdown) // true
// Queue is now done and cleared
const size = yield* Queue.size(queue)
console.log(size) // 0
})
shutdown(const queue: Queue.Queue<
OutElem,
Cause.Done<void> | OutErr
>
const queue: {
strategy: "suspend" | "dropping" | "sliding";
dispatcher: SchedulerDispatcher;
capacity: number;
messages: MutableList.MutableList<any>;
state: Queue.State<any, any>;
scheduleRunning: boolean;
toString: () => string;
toJSON: () => unknown;
}
import EffectEffect.const forkIn: {
(
scope: Scope,
options?: {
readonly startImmediately?:
| boolean
| undefined
readonly uninterruptible?:
| boolean
| "inherit"
| undefined
}
): <A, E, R>(
self: Effect<A, E, R>
) => Effect<Fiber<A, E>, never, R>
<A, E, R>(
self: Effect<A, E, R>,
scope: Scope,
options?: {
readonly startImmediately?:
| boolean
| undefined
readonly uninterruptible?:
| boolean
| "inherit"
| undefined
}
): Effect<Fiber<A, E>, never, R>
}
const runIntoQueue: {
<OutElem, OutErr>(
queue: Queue.Queue<
OutElem,
OutErr | Cause.Done
>
): <OutDone, Env>(
self: Channel<
OutElem,
OutErr,
OutDone,
unknown,
unknown,
unknown,
Env
>
) => Effect.Effect<void, never, Env>
<OutElem, OutErr, OutDone, Env>(
self: Channel<
OutElem,
OutErr,
OutDone,
unknown,
unknown,
unknown,
Env
>,
queue: Queue.Queue<
OutElem,
OutErr | Cause.Done
>
): Effect.Effect<void, never, Env>
}
self: Channel<
OutElem,
OutErr,
OutDone,
unknown,
unknown,
unknown,
Env
>
(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; <…;
}
const queue: Queue.Queue<
OutElem,
Cause.Done<void> | OutErr
>
const queue: {
strategy: "suspend" | "dropping" | "sliding";
dispatcher: SchedulerDispatcher;
capacity: number;
messages: MutableList.MutableList<any>;
state: Queue.State<any, any>;
scheduleRunning: boolean;
toString: () => string;
toJSON: () => unknown;
}
const scope: Scope.Scopeconst scope: {
strategy: "sequential" | "parallel";
state: State.Open | State.Closed | State.Empty;
}
const queue: Queue.Queue<
OutElem,
Cause.Done<void> | OutErr
>
const queue: {
strategy: "suspend" | "dropping" | "sliding";
dispatcher: SchedulerDispatcher;
capacity: number;
messages: MutableList.MutableList<any>;
state: Queue.State<any, any>;
scheduleRunning: boolean;
toString: () => string;
toJSON: () => unknown;
}