<I, S>(key: Key<I, S>, service: Option.Option<Types.NoInfer<S>>): <
Services
>(
self: Context<Services>
) => Context<Services | I>
<Services, I, S>(
self: Context<Services>,
key: Key<I, S>,
service: Option.Option<Types.NoInfer<S>>
): Context<Services | I>Adds or removes a service depending on an Option.
When to use
Use when you need to add or omit a Context service based on an Option.
Details
When service is Option.some, the value is stored for the key. When it is
Option.none, the key is removed from the returned Context.
Example (Adding optional services)
import { Context, Option } from "effect"
const Port = Context.Service<{ PORT: number }>("Port")
const withPort = Context.empty().pipe(
Context.addOrOmit(Port, Option.some({ PORT: 8080 }))
)
const withoutPort = withPort.pipe(
Context.addOrOmit(Port, Option.none())
)export const const addOrOmit: {
<I, S>(
key: Key<I, S>,
service: Option.Option<Types.NoInfer<S>>
): <Services>(
self: Context<Services>
) => Context<Services | I>
<Services, I, S>(
self: Context<Services>,
key: Key<I, S>,
service: Option.Option<Types.NoInfer<S>>
): Context<Services | I>
}
Adds or removes a service depending on an Option.
When to use
Use when you need to add or omit a Context service based on an Option.
Details
When service is Option.some, the value is stored for the key. When it is
Option.none, the key is removed from the returned Context.
Example (Adding optional services)
import { Context, Option } from "effect"
const Port = Context.Service<{ PORT: number }>("Port")
const withPort = Context.empty().pipe(
Context.addOrOmit(Port, Option.some({ PORT: 8080 }))
)
const withoutPort = withPort.pipe(
Context.addOrOmit(Port, Option.none())
)
addOrOmit: {
<function (type parameter) I in <I, S>(key: Key<I, S>, service: Option.Option<Types.NoInfer<S>>): <Services>(self: Context<Services>) => Context<Services | I>I, function (type parameter) S in <I, S>(key: Key<I, S>, service: Option.Option<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: Option.Option<Types.NoInfer<S>>): <Services>(self: Context<Services>) => Context<Services | I>I, function (type parameter) S in <I, S>(key: Key<I, S>, service: Option.Option<Types.NoInfer<S>>): <Services>(self: Context<Services>) => Context<Services | I>S>,
service: Option.Option<Types.NoInfer<S>>service: import OptionOption.type Option<A> = Option.None<A> | Option.Some<A>The Option data type represents optional values. An Option<A> is either
Some<A>, containing a value of type A, or None, representing absence.
When to use
Use to represent initial values that may not yet exist
- Returning from partial functions (not defined for all inputs)
- Managing optional fields in data structures
Namespace containing utility types for Option.
When to use
Use to access type-level helpers associated with Option.
Option<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: Option.Option<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: Option.Option<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: Option.Option<Types.NoInfer<S>>): Context<Services | I>Services, function (type parameter) I in <Services, I, S>(self: Context<Services>, key: Key<I, S>, service: Option.Option<Types.NoInfer<S>>): Context<Services | I>I, function (type parameter) S in <Services, I, S>(self: Context<Services>, key: Key<I, S>, service: Option.Option<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: Option.Option<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: Option.Option<Types.NoInfer<S>>): Context<Services | I>I, function (type parameter) S in <Services, I, S>(self: Context<Services>, key: Key<I, S>, service: Option.Option<Types.NoInfer<S>>): Context<Services | I>S>,
service: Option.Option<Types.NoInfer<S>>service: import OptionOption.type Option<A> = Option.None<A> | Option.Some<A>The Option data type represents optional values. An Option<A> is either
Some<A>, containing a value of type A, or None, representing absence.
When to use
Use to represent initial values that may not yet exist
- Returning from partial functions (not defined for all inputs)
- Managing optional fields in data structures
Namespace containing utility types for Option.
When to use
Use to access type-level helpers associated with Option.
Option<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: Option.Option<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: Option.Option<Types.NoInfer<S>>): Context<Services | I>Services | function (type parameter) I in <Services, I, S>(self: Context<Services>, key: Key<I, S>, service: Option.Option<Types.NoInfer<S>>): Context<Services | I>I>
} = dual<(...args: Array<any>) => any, <Services, I, S>(self: Context<Services>, key: Key<I, S>, service: Option.Option<Types.NoInfer<S>>) => Context<Services | I>>(arity: 3, body: <Services, I, S>(self: Context<Services>, key: Key<I, S>, service: Option.Option<Types.NoInfer<S>>) => Context<Services | I>): ((...args: Array<any>) => any) & (<Services, I, S>(self: Context<Services>, key: Key<I, S>, service: Option.Option<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: Option.Option<Types.NoInfer<S>>): Context<Services | I>Services, function (type parameter) I in <Services, I, S>(self: Context<Services>, key: Key<I, S>, service: Option.Option<Types.NoInfer<S>>): Context<Services | I>I, function (type parameter) S in <Services, I, S>(self: Context<Services>, key: Key<I, S>, service: Option.Option<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: Option.Option<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: Option.Option<Types.NoInfer<S>>): Context<Services | I>I, function (type parameter) S in <Services, I, S>(self: Context<Services>, key: Key<I, S>, service: Option.Option<Types.NoInfer<S>>): Context<Services | I>S>,
service: Option.Option<Types.NoInfer<S>>service: import OptionOption.type Option<A> = Option.None<A> | Option.Some<A>The Option data type represents optional values. An Option<A> is either
Some<A>, containing a value of type A, or None, representing absence.
When to use
Use to represent initial values that may not yet exist
- Returning from partial functions (not defined for all inputs)
- Managing optional fields in data structures
Namespace containing utility types for Option.
When to use
Use to access type-level helpers associated with Option.
Option<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: Option.Option<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: Option.Option<Types.NoInfer<S>>): Context<Services | I>Services | function (type parameter) I in <Services, I, S>(self: Context<Services>, key: Key<I, S>, service: Option.Option<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) => {
if (service: Option.Option<Types.NoInfer<S>>service._tag: "None" | "Some"_tag === "None") {
map: Map<string, any>map.Map<string, any>.delete(key: string): booleandelete(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)
} else {
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: Option.Option<Types.NoInfer<S>>(parameter) service: {
_tag: "Some";
_op: "Some";
value: A;
valueOrUndefined: A;
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;
}
Some<NoInfer<S>>.value: Types.NoInfer<S>value)
}
}))