<I, S>(key: Key<I, S>, service: Types.NoInfer<S>): <Services>(
self: Context<Services>
) => Context<Services | I>
<Services, I, S>(
self: Context<Services>,
key: Key<I, S>,
service: Types.NoInfer<S>
): Context<Services | I>Adds a service to a given Context.
When to use
Use when you need to store a known service value in a Context.
Details
If the context already contains the same service key, the new service replaces the previous one.
Example (Adding a service to a context)
import { Context, pipe } from "effect"
import * as assert from "node:assert"
const Port = Context.Service<{ PORT: number }>("Port")
const Timeout = Context.Service<{ TIMEOUT: number }>("Timeout")
const someContext = Context.make(Port, { PORT: 8080 })
const context = pipe(
someContext,
Context.add(Timeout, { TIMEOUT: 5000 })
)
assert.deepStrictEqual(Context.get(context, Port), { PORT: 8080 })
assert.deepStrictEqual(Context.get(context, Timeout), { TIMEOUT: 5000 })export const const add: {
<I, S>(
key: Key<I, S>,
service: Types.NoInfer<S>
): <Services>(
self: Context<Services>
) => Context<Services | I>
<Services, I, S>(
self: Context<Services>,
key: Key<I, S>,
service: Types.NoInfer<S>
): Context<Services | I>
}
Adds a service to a given Context.
When to use
Use when you need to store a known service value in a Context.
Details
If the context already contains the same service key, the new service
replaces the previous one.
Example (Adding a service to a context)
import { Context, pipe } from "effect"
import * as assert from "node:assert"
const Port = Context.Service<{ PORT: number }>("Port")
const Timeout = Context.Service<{ TIMEOUT: number }>("Timeout")
const someContext = Context.make(Port, { PORT: 8080 })
const context = pipe(
someContext,
Context.add(Timeout, { TIMEOUT: 5000 })
)
assert.deepStrictEqual(Context.get(context, Port), { PORT: 8080 })
assert.deepStrictEqual(Context.get(context, Timeout), { TIMEOUT: 5000 })
add: {
<function (type parameter) I in <I, S>(key: Key<I, S>, service: Types.NoInfer<S>): <Services>(self: Context<Services>) => Context<Services | I>I, function (type parameter) S in <I, S>(key: Key<I, S>, service: Types.NoInfer<S>): <Services>(self: Context<Services>) => Context<Services | I>S>(
key: Key<I, S>(parameter) key: {
Identifier: Identifier;
Service: Shape;
key: string;
stack: string | undefined;
pipe: { <A>(this: A): A; <A, B = never>(this: A, ab: (_: A) => B): B; <A, B = never, C = never>(this: A, ab: (_: A) => B, bc: (_: B) => C): C; <A, B = never, C = never, D = never>(this: A, ab: (_: A) => B, bc: (_: B) => C, cd: (_: C) => D): D; <…;
toString: () => string;
toJSON: () => unknown;
}
interface Key<out Identifier, out Shape>Typed identifier for a service stored in a Context.
When to use
Use as the typed handle for storing, retrieving, and requiring a specific
service in a Context.
Details
Identifier tracks the requirement in Effect types, while Shape is the
service implementation retrieved by the key. A key is also an Effect value,
so yielding it inside Effect.gen retrieves the service from the current
fiber context.
Key<function (type parameter) I in <I, S>(key: Key<I, S>, service: Types.NoInfer<S>): <Services>(self: Context<Services>) => Context<Services | I>I, function (type parameter) S in <I, S>(key: Key<I, S>, service: Types.NoInfer<S>): <Services>(self: Context<Services>) => Context<Services | I>S>,
service: Types.NoInfer<S>service: import TypesTypes.type NoInfer<A> = [A][A extends any
? 0
: never]
Prevents TypeScript from inferring a type parameter from a specific
position.
When to use
Use when a function parameter must match an inferred type without becoming
an inference source.
Details
The parameter using NoInfer must still match the inferred type.
Example (Controlling inference)
import type { Types } from "effect"
declare function withDefault<T>(value: T, fallback: Types.NoInfer<T>): T
// T is inferred as "a" | "b" from the first argument only
const result = withDefault<"a" | "b">("a", "b")
NoInfer<function (type parameter) S in <I, S>(key: Key<I, S>, service: Types.NoInfer<S>): <Services>(self: Context<Services>) => Context<Services | I>S>
): <function (type parameter) Services in <Services>(self: Context<Services>): Context<Services | I>Services>(self: Context<Services>(parameter) self: {
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;
}
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) Services in <Services>(self: Context<Services>): Context<Services | I>Services>) => 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) Services in <Services>(self: Context<Services>): Context<Services | I>Services | function (type parameter) I in <I, S>(key: Key<I, S>, service: Types.NoInfer<S>): <Services>(self: Context<Services>) => Context<Services | I>I>
<function (type parameter) Services in <Services, I, S>(self: Context<Services>, key: Key<I, S>, service: Types.NoInfer<S>): Context<Services | I>Services, function (type parameter) I in <Services, I, S>(self: Context<Services>, key: Key<I, S>, service: Types.NoInfer<S>): Context<Services | I>I, function (type parameter) S in <Services, I, S>(self: Context<Services>, key: Key<I, S>, service: Types.NoInfer<S>): Context<Services | I>S>(
self: Context<Services>(parameter) self: {
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;
}
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) Services in <Services, I, S>(self: Context<Services>, key: Key<I, S>, service: Types.NoInfer<S>): Context<Services | I>Services>,
key: Key<I, S>(parameter) key: {
Identifier: Identifier;
Service: Shape;
key: string;
stack: string | undefined;
pipe: { <A>(this: A): A; <A, B = never>(this: A, ab: (_: A) => B): B; <A, B = never, C = never>(this: A, ab: (_: A) => B, bc: (_: B) => C): C; <A, B = never, C = never, D = never>(this: A, ab: (_: A) => B, bc: (_: B) => C, cd: (_: C) => D): D; <…;
toString: () => string;
toJSON: () => unknown;
}
interface Key<out Identifier, out Shape>Typed identifier for a service stored in a Context.
When to use
Use as the typed handle for storing, retrieving, and requiring a specific
service in a Context.
Details
Identifier tracks the requirement in Effect types, while Shape is the
service implementation retrieved by the key. A key is also an Effect value,
so yielding it inside Effect.gen retrieves the service from the current
fiber context.
Key<function (type parameter) I in <Services, I, S>(self: Context<Services>, key: Key<I, S>, service: Types.NoInfer<S>): Context<Services | I>I, function (type parameter) S in <Services, I, S>(self: Context<Services>, key: Key<I, S>, service: Types.NoInfer<S>): Context<Services | I>S>,
service: Types.NoInfer<S>service: import TypesTypes.type NoInfer<A> = [A][A extends any
? 0
: never]
Prevents TypeScript from inferring a type parameter from a specific
position.
When to use
Use when a function parameter must match an inferred type without becoming
an inference source.
Details
The parameter using NoInfer must still match the inferred type.
Example (Controlling inference)
import type { Types } from "effect"
declare function withDefault<T>(value: T, fallback: Types.NoInfer<T>): T
// T is inferred as "a" | "b" from the first argument only
const result = withDefault<"a" | "b">("a", "b")
NoInfer<function (type parameter) S in <Services, I, S>(self: Context<Services>, key: Key<I, S>, service: Types.NoInfer<S>): Context<Services | I>S>
): 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) Services in <Services, I, S>(self: Context<Services>, key: Key<I, S>, service: Types.NoInfer<S>): Context<Services | I>Services | function (type parameter) I in <Services, I, S>(self: Context<Services>, key: Key<I, S>, service: Types.NoInfer<S>): Context<Services | I>I>
} = dual<(...args: Array<any>) => any, <Services, I, S>(self: Context<Services>, key: Key<I, S>, service: Types.NoInfer<S>) => Context<Services | I>>(arity: 3, body: <Services, I, S>(self: Context<Services>, key: Key<I, S>, service: Types.NoInfer<S>) => Context<Services | I>): ((...args: Array<any>) => any) & (<Services, I, S>(self: Context<Services>, key: Key<I, S>, service: Types.NoInfer<S>) => Context<Services | I>) (+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(3, <function (type parameter) Services in <Services, I, S>(self: Context<Services>, key: Key<I, S>, service: Types.NoInfer<S>): Context<Services | I>Services, function (type parameter) I in <Services, I, S>(self: Context<Services>, key: Key<I, S>, service: Types.NoInfer<S>): Context<Services | I>I, function (type parameter) S in <Services, I, S>(self: Context<Services>, key: Key<I, S>, service: Types.NoInfer<S>): Context<Services | I>S>(
self: Context<Services>(parameter) self: {
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;
}
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) Services in <Services, I, S>(self: Context<Services>, key: Key<I, S>, service: Types.NoInfer<S>): Context<Services | I>Services>,
key: Key<I, S>(parameter) key: {
Identifier: Identifier;
Service: Shape;
key: string;
stack: string | undefined;
pipe: { <A>(this: A): A; <A, B = never>(this: A, ab: (_: A) => B): B; <A, B = never, C = never>(this: A, ab: (_: A) => B, bc: (_: B) => C): C; <A, B = never, C = never, D = never>(this: A, ab: (_: A) => B, bc: (_: B) => C, cd: (_: C) => D): D; <…;
toString: () => string;
toJSON: () => unknown;
}
interface Key<out Identifier, out Shape>Typed identifier for a service stored in a Context.
When to use
Use as the typed handle for storing, retrieving, and requiring a specific
service in a Context.
Details
Identifier tracks the requirement in Effect types, while Shape is the
service implementation retrieved by the key. A key is also an Effect value,
so yielding it inside Effect.gen retrieves the service from the current
fiber context.
Key<function (type parameter) I in <Services, I, S>(self: Context<Services>, key: Key<I, S>, service: Types.NoInfer<S>): Context<Services | I>I, function (type parameter) S in <Services, I, S>(self: Context<Services>, key: Key<I, S>, service: Types.NoInfer<S>): Context<Services | I>S>,
service: Types.NoInfer<S>service: import TypesTypes.type NoInfer<A> = [A][A extends any
? 0
: never]
Prevents TypeScript from inferring a type parameter from a specific
position.
When to use
Use when a function parameter must match an inferred type without becoming
an inference source.
Details
The parameter using NoInfer must still match the inferred type.
Example (Controlling inference)
import type { Types } from "effect"
declare function withDefault<T>(value: T, fallback: Types.NoInfer<T>): T
// T is inferred as "a" | "b" from the first argument only
const result = withDefault<"a" | "b">("a", "b")
NoInfer<function (type parameter) S in <Services, I, S>(self: Context<Services>, key: Key<I, S>, service: Types.NoInfer<S>): Context<Services | I>S>
): 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) Services in <Services, I, S>(self: Context<Services>, key: Key<I, S>, service: Types.NoInfer<S>): Context<Services | I>Services | function (type parameter) I in <Services, I, S>(self: Context<Services>, key: Key<I, S>, service: Types.NoInfer<S>): Context<Services | I>I> =>
const withMapUnsafe: <Services, B>(
self: Context<Services>,
f: (map: Map<string, any>) => void
) => Context<B>
self: Context<Services>(parameter) self: {
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;
}
map: Map<string, any>map) => {
map: Map<string, any>map.Map<string, any>.set(key: string, value: any): Map<string, any>Adds a new element with a specified key and value to the Map. If an element with the same key already exists, the element will be updated.
set(key: Key<I, S>(parameter) key: {
Identifier: Identifier;
Service: Shape;
key: string;
stack: string | undefined;
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;
}
Key<out Identifier, out Shape>.key: stringkey, service: Types.NoInfer<S>service)
}))