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typed

Context overview

Re-exports from @effect/data/Context

Added in v1.0.0

Table of contents

constructors

empty

Returns an empty Context.

Signature

export declare const empty: () => Context<never>

Example

import * as Context from "effect/Context"

assert.strictEqual(Context.isContext(Context.empty()), true)

Added in v1.0.0

isContext

Returns an empty Context.

Signature

export declare const isContext: (input: unknown) => input is Context<never>

Example

import * as Context from "effect/Context"

assert.strictEqual(Context.isContext(Context.empty()), true)

Added in v1.0.0

make

Creates a new Context with a single service associated to the tag.

Signature

export declare const make: <T extends Tag<any, any>>(tag: T, service: Tag.Service<T>) => Context<Tag.Identifier<T>>

Example

import * as Context from "effect/Context"

const Port = Context.Tag<{ PORT: number }>()

const Services = Context.make(Port, { PORT: 8080 })

assert.deepStrictEqual(Context.get(Services, Port), { PORT: 8080 })

Added in v1.0.0

getters

get

Get a service from the context that corresponds to the given tag.

Signature

export declare const get: {
  <Services, T extends ValidTagsById<Services>>(tag: T): (self: Context<Services>) => Tag.Service<T>
  <Services, T extends ValidTagsById<Services>>(self: Context<Services>, tag: T): Tag.Service<T>
}

Example

import * as Context from "effect/Context"
import { pipe } from "effect/Function"

const Port = Context.Tag<{ PORT: number }>()
const Timeout = Context.Tag<{ TIMEOUT: number }>()

const Services = pipe(Context.make(Port, { PORT: 8080 }), Context.add(Timeout, { TIMEOUT: 5000 }))

assert.deepStrictEqual(Context.get(Services, Timeout), { TIMEOUT: 5000 })

Added in v1.0.0

getOption

Get the value associated with the specified tag from the context wrapped in an Option object. If the tag is not found, the Option object will be None.

Signature

export declare const getOption: {
  <S, I>(tag: Tag<I, S>): <Services>(self: Context<Services>) => Option<S>
  <Services, S, I>(self: Context<Services>, tag: Tag<I, S>): Option<S>
}

Example

import * as Context from "effect/Context"
import * as O from "effect/Option"

const Port = Context.Tag<{ PORT: number }>()
const Timeout = Context.Tag<{ TIMEOUT: number }>()

const Services = Context.make(Port, { PORT: 8080 })

assert.deepStrictEqual(Context.getOption(Services, Port), O.some({ PORT: 8080 }))
assert.deepStrictEqual(Context.getOption(Services, Timeout), O.none())

Added in v1.0.0

guards

isTag

Checks if the provided argument is a Tag.

Signature

export declare const isTag: (input: unknown) => input is Tag<any, any>

Example

import * as Context from "effect/Context"

assert.strictEqual(Context.isTag(Context.Tag()), true)

Added in v1.0.0

models

Context

Signature

export declare const Context: any

Added in v1.0.0

TagUnify

Signature

export declare const TagUnify: any

Added in v1.0.0

TagUnifyIgnore

Signature

export declare const TagUnifyIgnore: any

Added in v1.0.0

ValidTagsById

Signature

export declare const ValidTagsById: any

Added in v1.0.0

symbol

TagTypeId

Signature

export declare const TagTypeId: any

Added in v1.0.0

TypeId

Signature

export declare const TypeId: any

Added in v1.0.0

unsafe

unsafeGet

Get a service from the context that corresponds to the given tag. This function is unsafe because if the tag is not present in the context, a runtime error will be thrown.

For a safer version see {@link getOption}.

Signature

export declare const unsafeGet: {
  <S, I>(tag: Tag<I, S>): <Services>(self: Context<Services>) => S
  <Services, S, I>(self: Context<Services>, tag: Tag<I, S>): S
}

Example

import * as Context from "effect/Context"

const Port = Context.Tag<{ PORT: number }>()
const Timeout = Context.Tag<{ TIMEOUT: number }>()

const Services = Context.make(Port, { PORT: 8080 })

assert.deepStrictEqual(Context.unsafeGet(Services, Port), { PORT: 8080 })
assert.throws(() => Context.unsafeGet(Services, Timeout))

Added in v1.0.0

utils

TagClass

Signature

export declare const TagClass: any

Added in v1.0.0

add

Adds a service to a given Context.

Signature

export declare const add: {
  <T extends Tag<any, any>>(
    tag: T,
    service: Tag.Service<T>
  ): <Services>(self: Context<Services>) => Context<Services | Tag.Identifier<T>>
  <Services, T extends Tag<any, any>>(
    self: Context<Services>,
    tag: T,
    service: Tag.Service<T>
  ): Context<Services | Tag.Identifier<T>>
}

Example

import * as Context from "effect/Context"
import { pipe } from "effect/Function"

const Port = Context.Tag<{ PORT: number }>()
const Timeout = Context.Tag<{ TIMEOUT: number }>()

const someContext = Context.make(Port, { PORT: 8080 })

const Services = pipe(someContext, Context.add(Timeout, { TIMEOUT: 5000 }))

assert.deepStrictEqual(Context.get(Services, Port), { PORT: 8080 })
assert.deepStrictEqual(Context.get(Services, Timeout), { TIMEOUT: 5000 })

Added in v1.0.0

getMany

Get multiple services from the context that corresponds to the given tags.

Signature

export declare const getMany: {
  <Services, T extends readonly ValidTagsById<Services>[]>(
    ...tags: T
  ): (self: Context<Services>) => { readonly [K in keyof T]: Tag.Service<T[K]> }
  <Services, T extends readonly ValidTagsById<Services>[]>(
    self: Context<Services>,
    ...tags: T
  ): { readonly [K in keyof T]: Tag.Service<T[K]> }
}

Added in v1.0.0

merge

Merges two Contexts, returning a new Context containing the services of both.

Signature

export declare const merge: {
  <R1>(that: Context<R1>): <Services>(self: Context<Services>) => Context<R1 | Services>
  <Services, R1>(self: Context<Services>, that: Context<R1>): Context<Services | R1>
}

Example

import * as Context from "effect/Context"

const Port = Context.Tag<{ PORT: number }>()
const Timeout = Context.Tag<{ TIMEOUT: number }>()

const firstContext = Context.make(Port, { PORT: 8080 })
const secondContext = Context.make(Timeout, { TIMEOUT: 5000 })

const Services = Context.merge(firstContext, secondContext)

assert.deepStrictEqual(Context.get(Services, Port), { PORT: 8080 })
assert.deepStrictEqual(Context.get(Services, Timeout), { TIMEOUT: 5000 })

Added in v1.0.0

omit

Omits specified services from a given Context.

Signature

export declare const omit: <Services, S extends ValidTagsById<Services>[]>(
  ...tags: S
) => (self: Context<Services>) => Context<Exclude<Services, { [k in keyof S]: Tag.Identifier<S[k]> }[keyof S]>>

Added in v1.0.0

pick

Returns a new Context that contains only the specified services.

Signature

export declare const pick: <Services, S extends ValidTagsById<Services>[]>(
  ...tags: S
) => (self: Context<Services>) => Context<{ [k in keyof S]: Tag.Identifier<S[k]> }[number]>

Example

import * as Context from "effect/Context"
import { pipe } from "effect/Function"
import * as O from "effect/Option"

const Port = Context.Tag<{ PORT: number }>()
const Timeout = Context.Tag<{ TIMEOUT: number }>()

const someContext = pipe(Context.make(Port, { PORT: 8080 }), Context.add(Timeout, { TIMEOUT: 5000 }))

const Services = pipe(someContext, Context.pick(Port))

assert.deepStrictEqual(Context.getOption(Services, Port), O.some({ PORT: 8080 }))
assert.deepStrictEqual(Context.getOption(Services, Timeout), O.none())

Added in v1.0.0