<A, E = never, R = never>(
layer: Layer.Layer<A, E, R> | Context.Context<A>,
options?: { readonly local?: boolean | undefined } | undefined
): <OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>(
self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>
) => Channel<
OutElem,
OutErr | E,
OutDone,
InElem,
InErr,
InDone,
Exclude<Env, A> | R
>
<
OutElem,
OutErr,
OutDone,
InElem,
InErr,
InDone,
Env,
A,
E = never,
R = never
>(
self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>,
layer: Layer.Layer<A, E, R> | Context.Context<A>,
options?: { readonly local?: boolean | undefined } | undefined
): Channel<
OutElem,
OutErr | E,
OutDone,
InElem,
InErr,
InDone,
Exclude<Env, A> | R
>Provides a Layer or Context to the channel, removing the corresponding
service requirements.
Details
Providing a Context delegates to provideContext. Providing a Layer
builds the layer in the channel scope. Use options.local to build a fresh
layer instance for this provision.
services
Source effect/Channel.ts:729535 lines
export const const provide: {
<A, E = never, R = never>(
layer:
| Layer.Layer<A, E, R>
| Context.Context<A>,
options?:
| { readonly local?: boolean | undefined }
| undefined
): <
OutElem,
OutErr,
OutDone,
InElem,
InErr,
InDone,
Env
>(
self: Channel<
OutElem,
OutErr,
OutDone,
InElem,
InErr,
InDone,
Env
>
) => Channel<
OutElem,
OutErr | E,
OutDone,
InElem,
InErr,
InDone,
Exclude<Env, A> | R
>
<
OutElem,
OutErr,
OutDone,
InElem,
InErr,
InDone,
Env,
A,
E = never,
R = never
>(
self: Channel<
OutElem,
OutErr,
OutDone,
InElem,
InErr,
InDone,
Env
>,
layer:
| Layer.Layer<A, E, R>
| Context.Context<A>,
options?:
| { readonly local?: boolean | undefined }
| undefined
): Channel<
OutElem,
OutErr | E,
OutDone,
InElem,
InErr,
InDone,
Exclude<Env, A> | R
>
}
Provides a Layer or Context to the channel, removing the corresponding
service requirements.
Details
Providing a Context delegates to provideContext. Providing a Layer
builds the layer in the channel scope. Use options.local to build a fresh
layer instance for this provision.
provide: {
<function (type parameter) A in <A, E = never, R = never>(layer: Layer.Layer<A, E, R> | Context.Context<A>, options?: {
readonly local?: boolean | undefined;
} | undefined): <OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>) => Channel<OutElem, OutErr | E, OutDone, InElem, InErr, InDone, Exclude<Env, A> | R>
function (type parameter) E in <A, E = never, R = never>(layer: Layer.Layer<A, E, R> | Context.Context<A>, options?: {
readonly local?: boolean | undefined;
} | undefined): <OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>) => Channel<OutElem, OutErr | E, OutDone, InElem, InErr, InDone, Exclude<Env, A> | R>
function (type parameter) R in <A, E = never, R = never>(layer: Layer.Layer<A, E, R> | Context.Context<A>, options?: {
readonly local?: boolean | undefined;
} | undefined): <OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>) => Channel<OutElem, OutErr | E, OutDone, InElem, InErr, InDone, Exclude<Env, A> | R>
layer: | Layer.Layer<A, E, R>
| Context.Context<A>
import LayerLayer.interface Layer<in ROut, out E = never, out RIn = never>A Layer describes how to build one or more services for dependency injection.
When to use
Use to model construction of application services for dependency injection,
especially when services have dependencies, can fail during construction, or
need scoped setup and release.
Details
A Layer<ROut, E, RIn> represents ROut as the services this layer
provides, E as the possible errors during layer construction, and RIn as
the services this layer requires as dependencies.
Layer<function (type parameter) A in <A, E = never, R = never>(layer: Layer.Layer<A, E, R> | Context.Context<A>, options?: {
readonly local?: boolean | undefined;
} | undefined): <OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>) => Channel<OutElem, OutErr | E, OutDone, InElem, InErr, InDone, Exclude<Env, A> | R>
function (type parameter) E in <A, E = never, R = never>(layer: Layer.Layer<A, E, R> | Context.Context<A>, options?: {
readonly local?: boolean | undefined;
} | undefined): <OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>) => Channel<OutElem, OutErr | E, OutDone, InElem, InErr, InDone, Exclude<Env, A> | R>
function (type parameter) R in <A, E = never, R = never>(layer: Layer.Layer<A, E, R> | Context.Context<A>, options?: {
readonly local?: boolean | undefined;
} | undefined): <OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>) => Channel<OutElem, OutErr | E, OutDone, InElem, InErr, InDone, Exclude<Env, A> | R>
import ContextContext.interface Context<in Services>Immutable collection of service implementations used for dependency
injection in Effect programs.
Details
The type parameter tracks the service identifiers available in the context.
At runtime, services are stored by each key's string key.
Example (Creating a context with multiple services)
import { Context } from "effect"
// Create a context with multiple services
const Logger = Context.Service<{ log: (msg: string) => void }>("Logger")
const Database = Context.Service<{ query: (sql: string) => string }>(
"Database"
)
const context = Context.make(Logger, {
log: (msg: string) => console.log(msg)
})
.pipe(Context.add(Database, { query: (sql) => `Result: ${sql}` }))
Context<function (type parameter) A in <A, E = never, R = never>(layer: Layer.Layer<A, E, R> | Context.Context<A>, options?: {
readonly local?: boolean | undefined;
} | undefined): <OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>) => Channel<OutElem, OutErr | E, OutDone, InElem, InErr, InDone, Exclude<Env, A> | R>
options: | {
readonly local?: boolean | undefined
}
| undefined
local?: boolean | undefinedlocal?: boolean | undefined
} | undefined
): <function (type parameter) OutElem in <OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>): Channel<OutElem, OutErr | E, OutDone, InElem, InErr, InDone, Exclude<Env, A> | R>OutElem, function (type parameter) OutErr in <OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>): Channel<OutElem, OutErr | E, OutDone, InElem, InErr, InDone, Exclude<Env, A> | R>OutErr, function (type parameter) OutDone in <OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>): Channel<OutElem, OutErr | E, OutDone, InElem, InErr, InDone, Exclude<Env, A> | R>OutDone, function (type parameter) InElem in <OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>): Channel<OutElem, OutErr | E, OutDone, InElem, InErr, InDone, Exclude<Env, A> | R>InElem, function (type parameter) InErr in <OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>): Channel<OutElem, OutErr | E, OutDone, InElem, InErr, InDone, Exclude<Env, A> | R>InErr, function (type parameter) InDone in <OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>): Channel<OutElem, OutErr | E, OutDone, InElem, InErr, InDone, Exclude<Env, A> | R>InDone, function (type parameter) Env in <OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>): Channel<OutElem, OutErr | E, OutDone, InElem, InErr, InDone, Exclude<Env, A> | R>Env>(
self: Channel<
OutElem,
OutErr,
OutDone,
InElem,
InErr,
InDone,
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, InElem, InErr, InDone, Env>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>): Channel<OutElem, OutErr | E, OutDone, InElem, InErr, InDone, Exclude<Env, A> | R>OutElem, function (type parameter) OutErr in <OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>): Channel<OutElem, OutErr | E, OutDone, InElem, InErr, InDone, Exclude<Env, A> | R>OutErr, function (type parameter) OutDone in <OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>): Channel<OutElem, OutErr | E, OutDone, InElem, InErr, InDone, Exclude<Env, A> | R>OutDone, function (type parameter) InElem in <OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>): Channel<OutElem, OutErr | E, OutDone, InElem, InErr, InDone, Exclude<Env, A> | R>InElem, function (type parameter) InErr in <OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>): Channel<OutElem, OutErr | E, OutDone, InElem, InErr, InDone, Exclude<Env, A> | R>InErr, function (type parameter) InDone in <OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>): Channel<OutElem, OutErr | E, OutDone, InElem, InErr, InDone, Exclude<Env, A> | R>InDone, function (type parameter) Env in <OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>): Channel<OutElem, OutErr | E, OutDone, InElem, InErr, InDone, Exclude<Env, A> | R>Env>
) => 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, InElem, InErr, InDone, Env>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>): Channel<OutElem, OutErr | E, OutDone, InElem, InErr, InDone, Exclude<Env, A> | R>OutElem, function (type parameter) OutErr in <OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>): Channel<OutElem, OutErr | E, OutDone, InElem, InErr, InDone, Exclude<Env, A> | R>OutErr | function (type parameter) E in <A, E = never, R = never>(layer: Layer.Layer<A, E, R> | Context.Context<A>, options?: {
readonly local?: boolean | undefined;
} | undefined): <OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>) => Channel<OutElem, OutErr | E, OutDone, InElem, InErr, InDone, Exclude<Env, A> | R>
function (type parameter) OutDone in <OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>): Channel<OutElem, OutErr | E, OutDone, InElem, InErr, InDone, Exclude<Env, A> | R>OutDone, function (type parameter) InElem in <OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>): Channel<OutElem, OutErr | E, OutDone, InElem, InErr, InDone, Exclude<Env, A> | R>InElem, function (type parameter) InErr in <OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>): Channel<OutElem, OutErr | E, OutDone, InElem, InErr, InDone, Exclude<Env, A> | R>InErr, function (type parameter) InDone in <OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>): Channel<OutElem, OutErr | E, OutDone, InElem, InErr, InDone, Exclude<Env, A> | R>InDone, type Exclude<T, U> = T extends U
? never
: T
Exclude from T those types that are assignable to U
Exclude<function (type parameter) Env in <OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>): Channel<OutElem, OutErr | E, OutDone, InElem, InErr, InDone, Exclude<Env, A> | R>Env, function (type parameter) A in <A, E = never, R = never>(layer: Layer.Layer<A, E, R> | Context.Context<A>, options?: {
readonly local?: boolean | undefined;
} | undefined): <OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>) => Channel<OutElem, OutErr | E, OutDone, InElem, InErr, InDone, Exclude<Env, A> | R>
function (type parameter) R in <A, E = never, R = never>(layer: Layer.Layer<A, E, R> | Context.Context<A>, options?: {
readonly local?: boolean | undefined;
} | undefined): <OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>) => Channel<OutElem, OutErr | E, OutDone, InElem, InErr, InDone, Exclude<Env, A> | R>
function (type parameter) OutElem in <OutElem, OutErr, OutDone, InElem, InErr, InDone, Env, A, E = never, R = never>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>, layer: Layer.Layer<A, E, R> | Context.Context<A>, options?: {
readonly local?: boolean | undefined;
} | undefined): Channel<OutElem, OutErr | E, OutDone, InElem, InErr, InDone, Exclude<Env, A> | R>
function (type parameter) OutErr in <OutElem, OutErr, OutDone, InElem, InErr, InDone, Env, A, E = never, R = never>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>, layer: Layer.Layer<A, E, R> | Context.Context<A>, options?: {
readonly local?: boolean | undefined;
} | undefined): Channel<OutElem, OutErr | E, OutDone, InElem, InErr, InDone, Exclude<Env, A> | R>
function (type parameter) OutDone in <OutElem, OutErr, OutDone, InElem, InErr, InDone, Env, A, E = never, R = never>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>, layer: Layer.Layer<A, E, R> | Context.Context<A>, options?: {
readonly local?: boolean | undefined;
} | undefined): Channel<OutElem, OutErr | E, OutDone, InElem, InErr, InDone, Exclude<Env, A> | R>
function (type parameter) InElem in <OutElem, OutErr, OutDone, InElem, InErr, InDone, Env, A, E = never, R = never>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>, layer: Layer.Layer<A, E, R> | Context.Context<A>, options?: {
readonly local?: boolean | undefined;
} | undefined): Channel<OutElem, OutErr | E, OutDone, InElem, InErr, InDone, Exclude<Env, A> | R>
function (type parameter) InErr in <OutElem, OutErr, OutDone, InElem, InErr, InDone, Env, A, E = never, R = never>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>, layer: Layer.Layer<A, E, R> | Context.Context<A>, options?: {
readonly local?: boolean | undefined;
} | undefined): Channel<OutElem, OutErr | E, OutDone, InElem, InErr, InDone, Exclude<Env, A> | R>
function (type parameter) InDone in <OutElem, OutErr, OutDone, InElem, InErr, InDone, Env, A, E = never, R = never>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>, layer: Layer.Layer<A, E, R> | Context.Context<A>, options?: {
readonly local?: boolean | undefined;
} | undefined): Channel<OutElem, OutErr | E, OutDone, InElem, InErr, InDone, Exclude<Env, A> | R>
function (type parameter) Env in <OutElem, OutErr, OutDone, InElem, InErr, InDone, Env, A, E = never, R = never>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>, layer: Layer.Layer<A, E, R> | Context.Context<A>, options?: {
readonly local?: boolean | undefined;
} | undefined): Channel<OutElem, OutErr | E, OutDone, InElem, InErr, InDone, Exclude<Env, A> | R>
function (type parameter) A in <OutElem, OutErr, OutDone, InElem, InErr, InDone, Env, A, E = never, R = never>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>, layer: Layer.Layer<A, E, R> | Context.Context<A>, options?: {
readonly local?: boolean | undefined;
} | undefined): Channel<OutElem, OutErr | E, OutDone, InElem, InErr, InDone, Exclude<Env, A> | R>
function (type parameter) E in <OutElem, OutErr, OutDone, InElem, InErr, InDone, Env, A, E = never, R = never>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>, layer: Layer.Layer<A, E, R> | Context.Context<A>, options?: {
readonly local?: boolean | undefined;
} | undefined): Channel<OutElem, OutErr | E, OutDone, InElem, InErr, InDone, Exclude<Env, A> | R>
function (type parameter) R in <OutElem, OutErr, OutDone, InElem, InErr, InDone, Env, A, E = never, R = never>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>, layer: Layer.Layer<A, E, R> | Context.Context<A>, options?: {
readonly local?: boolean | undefined;
} | undefined): Channel<OutElem, OutErr | E, OutDone, InElem, InErr, InDone, Exclude<Env, A> | R>
self: Channel<
OutElem,
OutErr,
OutDone,
InElem,
InErr,
InDone,
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, InElem, InErr, InDone, Env, A, E = never, R = never>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>, layer: Layer.Layer<A, E, R> | Context.Context<A>, options?: {
readonly local?: boolean | undefined;
} | undefined): Channel<OutElem, OutErr | E, OutDone, InElem, InErr, InDone, Exclude<Env, A> | R>
function (type parameter) OutErr in <OutElem, OutErr, OutDone, InElem, InErr, InDone, Env, A, E = never, R = never>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>, layer: Layer.Layer<A, E, R> | Context.Context<A>, options?: {
readonly local?: boolean | undefined;
} | undefined): Channel<OutElem, OutErr | E, OutDone, InElem, InErr, InDone, Exclude<Env, A> | R>
function (type parameter) OutDone in <OutElem, OutErr, OutDone, InElem, InErr, InDone, Env, A, E = never, R = never>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>, layer: Layer.Layer<A, E, R> | Context.Context<A>, options?: {
readonly local?: boolean | undefined;
} | undefined): Channel<OutElem, OutErr | E, OutDone, InElem, InErr, InDone, Exclude<Env, A> | R>
function (type parameter) InElem in <OutElem, OutErr, OutDone, InElem, InErr, InDone, Env, A, E = never, R = never>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>, layer: Layer.Layer<A, E, R> | Context.Context<A>, options?: {
readonly local?: boolean | undefined;
} | undefined): Channel<OutElem, OutErr | E, OutDone, InElem, InErr, InDone, Exclude<Env, A> | R>
function (type parameter) InErr in <OutElem, OutErr, OutDone, InElem, InErr, InDone, Env, A, E = never, R = never>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>, layer: Layer.Layer<A, E, R> | Context.Context<A>, options?: {
readonly local?: boolean | undefined;
} | undefined): Channel<OutElem, OutErr | E, OutDone, InElem, InErr, InDone, Exclude<Env, A> | R>
function (type parameter) InDone in <OutElem, OutErr, OutDone, InElem, InErr, InDone, Env, A, E = never, R = never>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>, layer: Layer.Layer<A, E, R> | Context.Context<A>, options?: {
readonly local?: boolean | undefined;
} | undefined): Channel<OutElem, OutErr | E, OutDone, InElem, InErr, InDone, Exclude<Env, A> | R>
function (type parameter) Env in <OutElem, OutErr, OutDone, InElem, InErr, InDone, Env, A, E = never, R = never>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>, layer: Layer.Layer<A, E, R> | Context.Context<A>, options?: {
readonly local?: boolean | undefined;
} | undefined): Channel<OutElem, OutErr | E, OutDone, InElem, InErr, InDone, Exclude<Env, A> | R>
layer: | Layer.Layer<A, E, R>
| Context.Context<A>
import LayerLayer.interface Layer<in ROut, out E = never, out RIn = never>A Layer describes how to build one or more services for dependency injection.
When to use
Use to model construction of application services for dependency injection,
especially when services have dependencies, can fail during construction, or
need scoped setup and release.
Details
A Layer<ROut, E, RIn> represents ROut as the services this layer
provides, E as the possible errors during layer construction, and RIn as
the services this layer requires as dependencies.
Layer<function (type parameter) A in <OutElem, OutErr, OutDone, InElem, InErr, InDone, Env, A, E = never, R = never>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>, layer: Layer.Layer<A, E, R> | Context.Context<A>, options?: {
readonly local?: boolean | undefined;
} | undefined): Channel<OutElem, OutErr | E, OutDone, InElem, InErr, InDone, Exclude<Env, A> | R>
function (type parameter) E in <OutElem, OutErr, OutDone, InElem, InErr, InDone, Env, A, E = never, R = never>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>, layer: Layer.Layer<A, E, R> | Context.Context<A>, options?: {
readonly local?: boolean | undefined;
} | undefined): Channel<OutElem, OutErr | E, OutDone, InElem, InErr, InDone, Exclude<Env, A> | R>
function (type parameter) R in <OutElem, OutErr, OutDone, InElem, InErr, InDone, Env, A, E = never, R = never>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>, layer: Layer.Layer<A, E, R> | Context.Context<A>, options?: {
readonly local?: boolean | undefined;
} | undefined): Channel<OutElem, OutErr | E, OutDone, InElem, InErr, InDone, Exclude<Env, A> | R>
import ContextContext.interface Context<in Services>Immutable collection of service implementations used for dependency
injection in Effect programs.
Details
The type parameter tracks the service identifiers available in the context.
At runtime, services are stored by each key's string key.
Example (Creating a context with multiple services)
import { Context } from "effect"
// Create a context with multiple services
const Logger = Context.Service<{ log: (msg: string) => void }>("Logger")
const Database = Context.Service<{ query: (sql: string) => string }>(
"Database"
)
const context = Context.make(Logger, {
log: (msg: string) => console.log(msg)
})
.pipe(Context.add(Database, { query: (sql) => `Result: ${sql}` }))
Context<function (type parameter) A in <OutElem, OutErr, OutDone, InElem, InErr, InDone, Env, A, E = never, R = never>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>, layer: Layer.Layer<A, E, R> | Context.Context<A>, options?: {
readonly local?: boolean | undefined;
} | undefined): Channel<OutElem, OutErr | E, OutDone, InElem, InErr, InDone, Exclude<Env, A> | R>
options: | {
readonly local?: boolean | undefined
}
| undefined
local?: boolean | undefinedlocal?: boolean | undefined
} | undefined
): 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, InElem, InErr, InDone, Env, A, E = never, R = never>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>, layer: Layer.Layer<A, E, R> | Context.Context<A>, options?: {
readonly local?: boolean | undefined;
} | undefined): Channel<OutElem, OutErr | E, OutDone, InElem, InErr, InDone, Exclude<Env, A> | R>
function (type parameter) OutErr in <OutElem, OutErr, OutDone, InElem, InErr, InDone, Env, A, E = never, R = never>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>, layer: Layer.Layer<A, E, R> | Context.Context<A>, options?: {
readonly local?: boolean | undefined;
} | undefined): Channel<OutElem, OutErr | E, OutDone, InElem, InErr, InDone, Exclude<Env, A> | R>
function (type parameter) E in <OutElem, OutErr, OutDone, InElem, InErr, InDone, Env, A, E = never, R = never>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>, layer: Layer.Layer<A, E, R> | Context.Context<A>, options?: {
readonly local?: boolean | undefined;
} | undefined): Channel<OutElem, OutErr | E, OutDone, InElem, InErr, InDone, Exclude<Env, A> | R>
function (type parameter) OutDone in <OutElem, OutErr, OutDone, InElem, InErr, InDone, Env, A, E = never, R = never>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>, layer: Layer.Layer<A, E, R> | Context.Context<A>, options?: {
readonly local?: boolean | undefined;
} | undefined): Channel<OutElem, OutErr | E, OutDone, InElem, InErr, InDone, Exclude<Env, A> | R>
function (type parameter) InElem in <OutElem, OutErr, OutDone, InElem, InErr, InDone, Env, A, E = never, R = never>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>, layer: Layer.Layer<A, E, R> | Context.Context<A>, options?: {
readonly local?: boolean | undefined;
} | undefined): Channel<OutElem, OutErr | E, OutDone, InElem, InErr, InDone, Exclude<Env, A> | R>
function (type parameter) InErr in <OutElem, OutErr, OutDone, InElem, InErr, InDone, Env, A, E = never, R = never>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>, layer: Layer.Layer<A, E, R> | Context.Context<A>, options?: {
readonly local?: boolean | undefined;
} | undefined): Channel<OutElem, OutErr | E, OutDone, InElem, InErr, InDone, Exclude<Env, A> | R>
function (type parameter) InDone in <OutElem, OutErr, OutDone, InElem, InErr, InDone, Env, A, E = never, R = never>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>, layer: Layer.Layer<A, E, R> | Context.Context<A>, options?: {
readonly local?: boolean | undefined;
} | undefined): Channel<OutElem, OutErr | E, OutDone, InElem, InErr, InDone, Exclude<Env, A> | R>
type Exclude<T, U> = T extends U
? never
: T
Exclude from T those types that are assignable to U
Exclude<function (type parameter) Env in <OutElem, OutErr, OutDone, InElem, InErr, InDone, Env, A, E = never, R = never>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>, layer: Layer.Layer<A, E, R> | Context.Context<A>, options?: {
readonly local?: boolean | undefined;
} | undefined): Channel<OutElem, OutErr | E, OutDone, InElem, InErr, InDone, Exclude<Env, A> | R>
function (type parameter) A in <OutElem, OutErr, OutDone, InElem, InErr, InDone, Env, A, E = never, R = never>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>, layer: Layer.Layer<A, E, R> | Context.Context<A>, options?: {
readonly local?: boolean | undefined;
} | undefined): Channel<OutElem, OutErr | E, OutDone, InElem, InErr, InDone, Exclude<Env, A> | R>
function (type parameter) R in <OutElem, OutErr, OutDone, InElem, InErr, InDone, Env, A, E = never, R = never>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>, layer: Layer.Layer<A, E, R> | Context.Context<A>, options?: {
readonly local?: boolean | undefined;
} | undefined): Channel<OutElem, OutErr | E, OutDone, InElem, InErr, InDone, Exclude<Env, A> | R>
dual<(...args: Array<any>) => any, <OutElem, OutErr, OutDone, InElem, InErr, InDone, Env, A, E = never, R = never>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>, layer: Layer.Layer<A, E, R> | Context.Context<A>, options?: {
readonly local?: boolean | undefined;
} | undefined) => Channel<OutElem, OutErr | E, OutDone, InElem, InErr, InDone, Exclude<Env, A> | R>>(isDataFirst: (args: IArguments) => boolean, body: <OutElem, OutErr, OutDone, InElem, InErr, InDone, Env, A, E = never, R = never>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>, layer: Layer.Layer<A, E, R> | Context.Context<A>, options?: {
readonly local?: boolean | undefined;
} | undefined) => Channel<OutElem, OutErr | E, OutDone, InElem, InErr, InDone, Exclude<Env, A> | R>): ((...args: Array<any>) => any) & (<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env, A, E = never, R = never>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>, layer: Layer.Layer<A, E, R> | Context.Context<A>, options?: {
readonly local?: boolean | undefined;
} | undefined) => Channel<OutElem, OutErr | E, OutDone, InElem, InErr, InDone, Exclude<Env, A> | R>) (+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]), <function (type parameter) OutElem in <OutElem, OutErr, OutDone, InElem, InErr, InDone, Env, A, E = never, R = never>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>, layer: Layer.Layer<A, E, R> | Context.Context<A>, options?: {
readonly local?: boolean | undefined;
} | undefined): Channel<OutElem, OutErr | E, OutDone, InElem, InErr, InDone, Exclude<Env, A> | R>
function (type parameter) OutErr in <OutElem, OutErr, OutDone, InElem, InErr, InDone, Env, A, E = never, R = never>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>, layer: Layer.Layer<A, E, R> | Context.Context<A>, options?: {
readonly local?: boolean | undefined;
} | undefined): Channel<OutElem, OutErr | E, OutDone, InElem, InErr, InDone, Exclude<Env, A> | R>
function (type parameter) OutDone in <OutElem, OutErr, OutDone, InElem, InErr, InDone, Env, A, E = never, R = never>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>, layer: Layer.Layer<A, E, R> | Context.Context<A>, options?: {
readonly local?: boolean | undefined;
} | undefined): Channel<OutElem, OutErr | E, OutDone, InElem, InErr, InDone, Exclude<Env, A> | R>
function (type parameter) InElem in <OutElem, OutErr, OutDone, InElem, InErr, InDone, Env, A, E = never, R = never>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>, layer: Layer.Layer<A, E, R> | Context.Context<A>, options?: {
readonly local?: boolean | undefined;
} | undefined): Channel<OutElem, OutErr | E, OutDone, InElem, InErr, InDone, Exclude<Env, A> | R>
function (type parameter) InErr in <OutElem, OutErr, OutDone, InElem, InErr, InDone, Env, A, E = never, R = never>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>, layer: Layer.Layer<A, E, R> | Context.Context<A>, options?: {
readonly local?: boolean | undefined;
} | undefined): Channel<OutElem, OutErr | E, OutDone, InElem, InErr, InDone, Exclude<Env, A> | R>
function (type parameter) InDone in <OutElem, OutErr, OutDone, InElem, InErr, InDone, Env, A, E = never, R = never>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>, layer: Layer.Layer<A, E, R> | Context.Context<A>, options?: {
readonly local?: boolean | undefined;
} | undefined): Channel<OutElem, OutErr | E, OutDone, InElem, InErr, InDone, Exclude<Env, A> | R>
function (type parameter) Env in <OutElem, OutErr, OutDone, InElem, InErr, InDone, Env, A, E = never, R = never>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>, layer: Layer.Layer<A, E, R> | Context.Context<A>, options?: {
readonly local?: boolean | undefined;
} | undefined): Channel<OutElem, OutErr | E, OutDone, InElem, InErr, InDone, Exclude<Env, A> | R>
function (type parameter) A in <OutElem, OutErr, OutDone, InElem, InErr, InDone, Env, A, E = never, R = never>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>, layer: Layer.Layer<A, E, R> | Context.Context<A>, options?: {
readonly local?: boolean | undefined;
} | undefined): Channel<OutElem, OutErr | E, OutDone, InElem, InErr, InDone, Exclude<Env, A> | R>
function (type parameter) E in <OutElem, OutErr, OutDone, InElem, InErr, InDone, Env, A, E = never, R = never>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>, layer: Layer.Layer<A, E, R> | Context.Context<A>, options?: {
readonly local?: boolean | undefined;
} | undefined): Channel<OutElem, OutErr | E, OutDone, InElem, InErr, InDone, Exclude<Env, A> | R>
function (type parameter) R in <OutElem, OutErr, OutDone, InElem, InErr, InDone, Env, A, E = never, R = never>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>, layer: Layer.Layer<A, E, R> | Context.Context<A>, options?: {
readonly local?: boolean | undefined;
} | undefined): Channel<OutElem, OutErr | E, OutDone, InElem, InErr, InDone, Exclude<Env, A> | R>
self: Channel<
OutElem,
OutErr,
OutDone,
InElem,
InErr,
InDone,
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, InElem, InErr, InDone, Env, A, E = never, R = never>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>, layer: Layer.Layer<A, E, R> | Context.Context<A>, options?: {
readonly local?: boolean | undefined;
} | undefined): Channel<OutElem, OutErr | E, OutDone, InElem, InErr, InDone, Exclude<Env, A> | R>
function (type parameter) OutErr in <OutElem, OutErr, OutDone, InElem, InErr, InDone, Env, A, E = never, R = never>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>, layer: Layer.Layer<A, E, R> | Context.Context<A>, options?: {
readonly local?: boolean | undefined;
} | undefined): Channel<OutElem, OutErr | E, OutDone, InElem, InErr, InDone, Exclude<Env, A> | R>
function (type parameter) OutDone in <OutElem, OutErr, OutDone, InElem, InErr, InDone, Env, A, E = never, R = never>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>, layer: Layer.Layer<A, E, R> | Context.Context<A>, options?: {
readonly local?: boolean | undefined;
} | undefined): Channel<OutElem, OutErr | E, OutDone, InElem, InErr, InDone, Exclude<Env, A> | R>
function (type parameter) InElem in <OutElem, OutErr, OutDone, InElem, InErr, InDone, Env, A, E = never, R = never>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>, layer: Layer.Layer<A, E, R> | Context.Context<A>, options?: {
readonly local?: boolean | undefined;
} | undefined): Channel<OutElem, OutErr | E, OutDone, InElem, InErr, InDone, Exclude<Env, A> | R>
function (type parameter) InErr in <OutElem, OutErr, OutDone, InElem, InErr, InDone, Env, A, E = never, R = never>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>, layer: Layer.Layer<A, E, R> | Context.Context<A>, options?: {
readonly local?: boolean | undefined;
} | undefined): Channel<OutElem, OutErr | E, OutDone, InElem, InErr, InDone, Exclude<Env, A> | R>
function (type parameter) InDone in <OutElem, OutErr, OutDone, InElem, InErr, InDone, Env, A, E = never, R = never>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>, layer: Layer.Layer<A, E, R> | Context.Context<A>, options?: {
readonly local?: boolean | undefined;
} | undefined): Channel<OutElem, OutErr | E, OutDone, InElem, InErr, InDone, Exclude<Env, A> | R>
function (type parameter) Env in <OutElem, OutErr, OutDone, InElem, InErr, InDone, Env, A, E = never, R = never>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>, layer: Layer.Layer<A, E, R> | Context.Context<A>, options?: {
readonly local?: boolean | undefined;
} | undefined): Channel<OutElem, OutErr | E, OutDone, InElem, InErr, InDone, Exclude<Env, A> | R>
layer: | Layer.Layer<A, E, R>
| Context.Context<A>
import LayerLayer.interface Layer<in ROut, out E = never, out RIn = never>A Layer describes how to build one or more services for dependency injection.
When to use
Use to model construction of application services for dependency injection,
especially when services have dependencies, can fail during construction, or
need scoped setup and release.
Details
A Layer<ROut, E, RIn> represents ROut as the services this layer
provides, E as the possible errors during layer construction, and RIn as
the services this layer requires as dependencies.
Layer<function (type parameter) A in <OutElem, OutErr, OutDone, InElem, InErr, InDone, Env, A, E = never, R = never>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>, layer: Layer.Layer<A, E, R> | Context.Context<A>, options?: {
readonly local?: boolean | undefined;
} | undefined): Channel<OutElem, OutErr | E, OutDone, InElem, InErr, InDone, Exclude<Env, A> | R>
function (type parameter) E in <OutElem, OutErr, OutDone, InElem, InErr, InDone, Env, A, E = never, R = never>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>, layer: Layer.Layer<A, E, R> | Context.Context<A>, options?: {
readonly local?: boolean | undefined;
} | undefined): Channel<OutElem, OutErr | E, OutDone, InElem, InErr, InDone, Exclude<Env, A> | R>
function (type parameter) R in <OutElem, OutErr, OutDone, InElem, InErr, InDone, Env, A, E = never, R = never>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>, layer: Layer.Layer<A, E, R> | Context.Context<A>, options?: {
readonly local?: boolean | undefined;
} | undefined): Channel<OutElem, OutErr | E, OutDone, InElem, InErr, InDone, Exclude<Env, A> | R>
import ContextContext.interface Context<in Services>Immutable collection of service implementations used for dependency
injection in Effect programs.
Details
The type parameter tracks the service identifiers available in the context.
At runtime, services are stored by each key's string key.
Example (Creating a context with multiple services)
import { Context } from "effect"
// Create a context with multiple services
const Logger = Context.Service<{ log: (msg: string) => void }>("Logger")
const Database = Context.Service<{ query: (sql: string) => string }>(
"Database"
)
const context = Context.make(Logger, {
log: (msg: string) => console.log(msg)
})
.pipe(Context.add(Database, { query: (sql) => `Result: ${sql}` }))
Context<function (type parameter) A in <OutElem, OutErr, OutDone, InElem, InErr, InDone, Env, A, E = never, R = never>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>, layer: Layer.Layer<A, E, R> | Context.Context<A>, options?: {
readonly local?: boolean | undefined;
} | undefined): Channel<OutElem, OutErr | E, OutDone, InElem, InErr, InDone, Exclude<Env, A> | R>
options: | {
readonly local?: boolean | undefined
}
| undefined
local?: boolean | undefinedlocal?: boolean | undefined
} | undefined
): 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, InElem, InErr, InDone, Env, A, E = never, R = never>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>, layer: Layer.Layer<A, E, R> | Context.Context<A>, options?: {
readonly local?: boolean | undefined;
} | undefined): Channel<OutElem, OutErr | E, OutDone, InElem, InErr, InDone, Exclude<Env, A> | R>
function (type parameter) OutErr in <OutElem, OutErr, OutDone, InElem, InErr, InDone, Env, A, E = never, R = never>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>, layer: Layer.Layer<A, E, R> | Context.Context<A>, options?: {
readonly local?: boolean | undefined;
} | undefined): Channel<OutElem, OutErr | E, OutDone, InElem, InErr, InDone, Exclude<Env, A> | R>
function (type parameter) E in <OutElem, OutErr, OutDone, InElem, InErr, InDone, Env, A, E = never, R = never>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>, layer: Layer.Layer<A, E, R> | Context.Context<A>, options?: {
readonly local?: boolean | undefined;
} | undefined): Channel<OutElem, OutErr | E, OutDone, InElem, InErr, InDone, Exclude<Env, A> | R>
function (type parameter) OutDone in <OutElem, OutErr, OutDone, InElem, InErr, InDone, Env, A, E = never, R = never>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>, layer: Layer.Layer<A, E, R> | Context.Context<A>, options?: {
readonly local?: boolean | undefined;
} | undefined): Channel<OutElem, OutErr | E, OutDone, InElem, InErr, InDone, Exclude<Env, A> | R>
function (type parameter) InElem in <OutElem, OutErr, OutDone, InElem, InErr, InDone, Env, A, E = never, R = never>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>, layer: Layer.Layer<A, E, R> | Context.Context<A>, options?: {
readonly local?: boolean | undefined;
} | undefined): Channel<OutElem, OutErr | E, OutDone, InElem, InErr, InDone, Exclude<Env, A> | R>
function (type parameter) InErr in <OutElem, OutErr, OutDone, InElem, InErr, InDone, Env, A, E = never, R = never>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>, layer: Layer.Layer<A, E, R> | Context.Context<A>, options?: {
readonly local?: boolean | undefined;
} | undefined): Channel<OutElem, OutErr | E, OutDone, InElem, InErr, InDone, Exclude<Env, A> | R>
function (type parameter) InDone in <OutElem, OutErr, OutDone, InElem, InErr, InDone, Env, A, E = never, R = never>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>, layer: Layer.Layer<A, E, R> | Context.Context<A>, options?: {
readonly local?: boolean | undefined;
} | undefined): Channel<OutElem, OutErr | E, OutDone, InElem, InErr, InDone, Exclude<Env, A> | R>
type Exclude<T, U> = T extends U
? never
: T
Exclude from T those types that are assignable to U
Exclude<function (type parameter) Env in <OutElem, OutErr, OutDone, InElem, InErr, InDone, Env, A, E = never, R = never>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>, layer: Layer.Layer<A, E, R> | Context.Context<A>, options?: {
readonly local?: boolean | undefined;
} | undefined): Channel<OutElem, OutErr | E, OutDone, InElem, InErr, InDone, Exclude<Env, A> | R>
function (type parameter) A in <OutElem, OutErr, OutDone, InElem, InErr, InDone, Env, A, E = never, R = never>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>, layer: Layer.Layer<A, E, R> | Context.Context<A>, options?: {
readonly local?: boolean | undefined;
} | undefined): Channel<OutElem, OutErr | E, OutDone, InElem, InErr, InDone, Exclude<Env, A> | R>
function (type parameter) R in <OutElem, OutErr, OutDone, InElem, InErr, InDone, Env, A, E = never, R = never>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>, layer: Layer.Layer<A, E, R> | Context.Context<A>, options?: {
readonly local?: boolean | undefined;
} | undefined): Channel<OutElem, OutErr | E, OutDone, InElem, InErr, InDone, Exclude<Env, A> | R>
import ContextContext.const isContext: (
u: unknown
) => u is Context<never>
Checks whether the provided argument is a Context.
When to use
Use to narrow an unknown value before passing it to APIs that require a
Context.
Details
This checks the runtime Context marker and does not inspect which services
the context contains.
Gotchas
This guard only proves that the value is a Context; it does not prove that
any specific service is present.
Example (Checking for contexts)
import { Context } from "effect"
import * as assert from "node:assert"
assert.strictEqual(Context.isContext(Context.empty()), true)
isContext(layer: | Layer.Layer<A, E, R>
| Context.Context<A>
const provideContext: {
<R2>(context: Context.Context<R2>): <
OutElem,
OutErr,
OutDone,
InElem,
InErr,
InDone,
Env
>(
self: Channel<
OutElem,
OutErr,
OutDone,
InElem,
InErr,
InDone,
Env
>
) => Channel<
OutElem,
OutErr,
OutDone,
InElem,
InErr,
InDone,
Exclude<Env, R2>
>
<
OutElem,
OutErr,
OutDone,
InElem,
InErr,
InDone,
Env,
R2
>(
self: Channel<
OutElem,
OutErr,
OutDone,
InElem,
InErr,
InDone,
Env
>,
context: Context.Context<R2>
): Channel<
OutElem,
OutErr,
OutDone,
InElem,
InErr,
InDone,
Exclude<Env, R2>
>
}
self: Channel<
OutElem,
OutErr,
OutDone,
InElem,
InErr,
InDone,
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; <…;
}
layer: | Layer.Layer<A, E, R>
| Context.Context<A>
(parameter) layer: {
mapUnsafe: ReadonlyMap<string, any>;
mutable: boolean;
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 fromTransform: <
OutElem,
OutErr,
OutDone,
InElem,
InErr,
InDone,
EX,
EnvX,
Env
>(
transform: (
upstream: Pull.Pull<InElem, InErr, InDone>,
scope: Scope.Scope
) => Effect.Effect<
Pull.Pull<OutElem, OutErr, OutDone, EnvX>,
EX,
Env
>
) => Channel<
OutElem,
Pull.ExcludeDone<OutErr> | EX,
OutDone,
InElem,
InErr,
InDone,
Env | EnvX
>
Creates a Channel from a transformation function that operates on upstream pulls.
Example (Creating channels from transforms)
import { Channel, Effect } from "effect"
const channel = Channel.fromTransform((upstream, scope) =>
Effect.succeed(upstream)
)
fromTransform((upstream: Pull.Pull<InElem, InErr, InDone, never>(parameter) upstream: {
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;
}
scope: Scope.Scope(parameter) scope: {
strategy: "sequential" | "parallel";
state: State.Open | State.Closed | State.Empty;
}
import EffectEffect.const flatMap: {
<A, B, E1, R1>(
f: (a: A) => Effect<B, E1, R1>
): <E, R>(
self: Effect<A, E, R>
) => Effect<B, E1 | E, R1 | R>
<A, E, R, B, E1, R1>(
self: Effect<A, E, R>,
f: (a: A) => Effect<B, E1, R1>
): Effect<B, E | E1, R | R1>
}
options: | {
readonly local?: boolean | undefined
}
| undefined
local?: boolean | undefinedlocal
? import LayerLayer.const buildWithMemoMap: {
(memoMap: MemoMap, scope: Scope.Scope): <
RIn,
E,
ROut
>(
self: Layer<ROut, E, RIn>
) => Effect<Context.Context<ROut>, E, RIn>
<RIn, E, ROut>(
self: Layer<ROut, E, RIn>,
memoMap: MemoMap,
scope: Scope.Scope
): Effect<Context.Context<ROut>, E, RIn>
}
layer: | Layer.Layer<A, E, R>
| Context.Context<A>
(parameter) layer: {
build: (memoMap: MemoMap, scope: Scope.Scope) => Effect<Context.Context<A>, E, R>;
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; <…;
}
import LayerLayer.const makeMemoMapUnsafe: () => MemoMapConstructs a MemoMap synchronously so it can be used to build additional layers.
Example (Creating a memo map unsafely)
import { Context, Effect, Layer } from "effect"
class Database extends Context.Service<Database, {
readonly query: (sql: string) => Effect.Effect<string>
}>()("Database") {}
// Create a memo map for manual layer building
const program = Effect.gen(function*() {
const memoMap = Layer.makeMemoMapUnsafe()
const scope = yield* Effect.scope
const dbLayer = Layer.succeed(Database, {
query: Effect.fn("Database.query")((sql: string) => Effect.succeed("result"))
})
const context = yield* Layer.buildWithMemoMap(dbLayer, memoMap, scope)
return Context.get(context, Database)
})
makeMemoMapUnsafe(), scope: Scope.Scope(parameter) scope: {
strategy: "sequential" | "parallel";
state: State.Open | State.Closed | State.Empty;
}
import LayerLayer.const buildWithScope: {
(scope: Scope.Scope): <RIn, E, ROut>(
self: Layer<ROut, E, RIn>
) => Effect<Context.Context<ROut>, E, RIn>
<RIn, E, ROut>(
self: Layer<ROut, E, RIn>,
scope: Scope.Scope
): Effect<Context.Context<ROut>, E, RIn>
}
layer: | Layer.Layer<A, E, R>
| Context.Context<A>
(parameter) layer: {
build: (memoMap: MemoMap, scope: Scope.Scope) => Effect<Context.Context<A>, E, R>;
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; <…;
}
scope: Scope.Scope(parameter) scope: {
strategy: "sequential" | "parallel";
state: State.Open | State.Closed | State.Empty;
}
context: Context.Context<A>(parameter) context: {
mapUnsafe: ReadonlyMap<string, any>;
mutable: boolean;
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.const map: {
<A, B>(f: (a: A) => B): <E, R>(
self: Effect<A, E, R>
) => Effect<B, E, R>
<A, E, R, B>(
self: Effect<A, E, R>,
f: (a: A) => B
): Effect<B, E, R>
}
import EffectEffect.const provideContext: {
<XR>(context: Context.Context<XR>): <A, E, R>(
self: Effect<A, E, R>
) => Effect<A, E, Exclude<R, XR>>
<A, E, R, XR>(
self: Effect<A, E, R>,
context: Context.Context<XR>
): Effect<A, E, Exclude<R, XR>>
}
const toTransform: <
OutElem,
OutErr,
OutDone,
InElem,
InErr,
InDone,
Env
>(
channel: Channel<
OutElem,
OutErr,
OutDone,
InElem,
InErr,
InDone,
Env
>
) => (
upstream: Pull.Pull<InElem, InErr, InDone>,
scope: Scope.Scope
) => Effect.Effect<
Pull.Pull<OutElem, OutErr, OutDone>,
never,
Env
>
Converts a Channel back to its underlying transformation function.
Example (Extracting channel transforms)
import { Channel } from "effect"
const channel = Channel.succeed(42)
const transform = Channel.toTransform(channel)
// transform can now be used directly
toTransform(self: Channel<
OutElem,
OutErr,
OutDone,
InElem,
InErr,
InDone,
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; <…;
}
upstream: Pull.Pull<InElem, InErr, InDone, never>(parameter) upstream: {
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;
}
scope: Scope.Scope(parameter) scope: {
strategy: "sequential" | "parallel";
state: State.Open | State.Closed | State.Empty;
}
context: Context.Context<A>(parameter) context: {
mapUnsafe: ReadonlyMap<string, any>;
mutable: boolean;
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.const provideContext: {
<XR>(context: Context.Context<XR>): <A, E, R>(
self: Effect<A, E, R>
) => Effect<A, E, Exclude<R, XR>>
<A, E, R, XR>(
self: Effect<A, E, R>,
context: Context.Context<XR>
): Effect<A, E, Exclude<R, XR>>
}
context: Context.Context<A>(parameter) context: {
mapUnsafe: ReadonlyMap<string, any>;
mutable: boolean;
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;
}
Referenced by 1 symbols