<ROut, XR extends ROut, RIn2, E2, X>(
f: (context: Context.Context<XR>) => Effect<X, E2, RIn2>
): <RIn, E>(
self: Layer<ROut, E, RIn>
) => Layer<ROut, E | E2, RIn | Exclude<RIn2, Scope.Scope>>
<RIn, E, ROut, XR extends ROut, RIn2, E2, X>(
self: Layer<ROut, E, RIn>,
f: (context: Context.Context<XR>) => Effect<X, E2, RIn2>
): Layer<ROut, E | E2, RIn | Exclude<RIn2, Scope.Scope>>Performs the specified effect if this layer succeeds.
When to use
Use to run an effectful observation after a layer has been built successfully, such as logging or metrics, without changing the services the layer provides.
Details
The callback receives the services produced by this layer. Its result is discarded, and the original layer output is preserved.
export const const tap: {
<ROut, XR extends ROut, RIn2, E2, X>(
f: (
context: Context.Context<XR>
) => Effect<X, E2, RIn2>
): <RIn, E>(
self: Layer<ROut, E, RIn>
) => Layer<
ROut,
E | E2,
RIn | Exclude<RIn2, Scope.Scope>
>
<RIn, E, ROut, XR extends ROut, RIn2, E2, X>(
self: Layer<ROut, E, RIn>,
f: (
context: Context.Context<XR>
) => Effect<X, E2, RIn2>
): Layer<
ROut,
E | E2,
RIn | Exclude<RIn2, Scope.Scope>
>
}
Performs the specified effect if this layer succeeds.
When to use
Use to run an effectful observation after a layer has been built
successfully, such as logging or metrics, without changing the services the
layer provides.
Details
The callback receives the services produced by this layer. Its result is
discarded, and the original layer output is preserved.
tap: {
<function (type parameter) ROut in <ROut, XR extends ROut, RIn2, E2, X>(f: (context: Context.Context<XR>) => Effect<X, E2, RIn2>): <RIn, E>(self: Layer<ROut, E, RIn>) => Layer<ROut, E | E2, RIn | Exclude<RIn2, Scope.Scope>>ROut, function (type parameter) XR in <ROut, XR extends ROut, RIn2, E2, X>(f: (context: Context.Context<XR>) => Effect<X, E2, RIn2>): <RIn, E>(self: Layer<ROut, E, RIn>) => Layer<ROut, E | E2, RIn | Exclude<RIn2, Scope.Scope>>XR extends function (type parameter) ROut in <ROut, XR extends ROut, RIn2, E2, X>(f: (context: Context.Context<XR>) => Effect<X, E2, RIn2>): <RIn, E>(self: Layer<ROut, E, RIn>) => Layer<ROut, E | E2, RIn | Exclude<RIn2, Scope.Scope>>ROut, function (type parameter) RIn2 in <ROut, XR extends ROut, RIn2, E2, X>(f: (context: Context.Context<XR>) => Effect<X, E2, RIn2>): <RIn, E>(self: Layer<ROut, E, RIn>) => Layer<ROut, E | E2, RIn | Exclude<RIn2, Scope.Scope>>RIn2, function (type parameter) E2 in <ROut, XR extends ROut, RIn2, E2, X>(f: (context: Context.Context<XR>) => Effect<X, E2, RIn2>): <RIn, E>(self: Layer<ROut, E, RIn>) => Layer<ROut, E | E2, RIn | Exclude<RIn2, Scope.Scope>>E2, function (type parameter) X in <ROut, XR extends ROut, RIn2, E2, X>(f: (context: Context.Context<XR>) => Effect<X, E2, RIn2>): <RIn, E>(self: Layer<ROut, E, RIn>) => Layer<ROut, E | E2, RIn | Exclude<RIn2, Scope.Scope>>X>(
f: (
context: Context.Context<XR>
) => Effect<X, E2, RIn2>
context: Context.Context<XR>(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 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) XR in <ROut, XR extends ROut, RIn2, E2, X>(f: (context: Context.Context<XR>) => Effect<X, E2, RIn2>): <RIn, E>(self: Layer<ROut, E, RIn>) => Layer<ROut, E | E2, RIn | Exclude<RIn2, Scope.Scope>>XR>) => interface Effect<out A, out E = never, out R = never>The Effect interface defines a value that lazily describes a workflow or
job. The workflow requires some context R, and may fail with an error of
type E, or succeed with a value of type A.
When to use
Use when you need to represent a lazy, composable workflow that can require
services, fail with a typed error, or succeed with a typed value.
Details
Effect values model resourceful interaction with the outside world,
including synchronous, asynchronous, concurrent, and parallel interaction.
They use a fiber-based concurrency model, with built-in support for
scheduling, fine-grained interruption, structured concurrency, and high
scalability.
To run an Effect value, you need a Runtime, which is a type that is
capable of executing Effect values.
Effect<function (type parameter) X in <ROut, XR extends ROut, RIn2, E2, X>(f: (context: Context.Context<XR>) => Effect<X, E2, RIn2>): <RIn, E>(self: Layer<ROut, E, RIn>) => Layer<ROut, E | E2, RIn | Exclude<RIn2, Scope.Scope>>X, function (type parameter) E2 in <ROut, XR extends ROut, RIn2, E2, X>(f: (context: Context.Context<XR>) => Effect<X, E2, RIn2>): <RIn, E>(self: Layer<ROut, E, RIn>) => Layer<ROut, E | E2, RIn | Exclude<RIn2, Scope.Scope>>E2, function (type parameter) RIn2 in <ROut, XR extends ROut, RIn2, E2, X>(f: (context: Context.Context<XR>) => Effect<X, E2, RIn2>): <RIn, E>(self: Layer<ROut, E, RIn>) => Layer<ROut, E | E2, RIn | Exclude<RIn2, Scope.Scope>>RIn2>
): <function (type parameter) RIn in <RIn, E>(self: Layer<ROut, E, RIn>): Layer<ROut, E | E2, RIn | Exclude<RIn2, Scope.Scope>>RIn, function (type parameter) E in <RIn, E>(self: Layer<ROut, E, RIn>): Layer<ROut, E | E2, RIn | Exclude<RIn2, Scope.Scope>>E>(self: Layer<ROut, E, RIn>(parameter) self: {
build: (memoMap: MemoMap, scope: Scope.Scope) => Effect<Context.Context<ROut>, E, RIn>;
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 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) ROut in <ROut, XR extends ROut, RIn2, E2, X>(f: (context: Context.Context<XR>) => Effect<X, E2, RIn2>): <RIn, E>(self: Layer<ROut, E, RIn>) => Layer<ROut, E | E2, RIn | Exclude<RIn2, Scope.Scope>>ROut, function (type parameter) E in <RIn, E>(self: Layer<ROut, E, RIn>): Layer<ROut, E | E2, RIn | Exclude<RIn2, Scope.Scope>>E, function (type parameter) RIn in <RIn, E>(self: Layer<ROut, E, RIn>): Layer<ROut, E | E2, RIn | Exclude<RIn2, Scope.Scope>>RIn>) => 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) ROut in <ROut, XR extends ROut, RIn2, E2, X>(f: (context: Context.Context<XR>) => Effect<X, E2, RIn2>): <RIn, E>(self: Layer<ROut, E, RIn>) => Layer<ROut, E | E2, RIn | Exclude<RIn2, Scope.Scope>>ROut, function (type parameter) E in <RIn, E>(self: Layer<ROut, E, RIn>): Layer<ROut, E | E2, RIn | Exclude<RIn2, Scope.Scope>>E | function (type parameter) E2 in <ROut, XR extends ROut, RIn2, E2, X>(f: (context: Context.Context<XR>) => Effect<X, E2, RIn2>): <RIn, E>(self: Layer<ROut, E, RIn>) => Layer<ROut, E | E2, RIn | Exclude<RIn2, Scope.Scope>>E2, function (type parameter) RIn in <RIn, E>(self: Layer<ROut, E, RIn>): Layer<ROut, E | E2, RIn | Exclude<RIn2, Scope.Scope>>RIn | type Exclude<T, U> = T extends U
? never
: T
Exclude from T those types that are assignable to U
Exclude<function (type parameter) RIn2 in <ROut, XR extends ROut, RIn2, E2, X>(f: (context: Context.Context<XR>) => Effect<X, E2, RIn2>): <RIn, E>(self: Layer<ROut, E, RIn>) => Layer<ROut, E | E2, RIn | Exclude<RIn2, Scope.Scope>>RIn2, import ScopeScope.Scope>>
<function (type parameter) RIn in <RIn, E, ROut, XR extends ROut, RIn2, E2, X>(self: Layer<ROut, E, RIn>, f: (context: Context.Context<XR>) => Effect<X, E2, RIn2>): Layer<ROut, E | E2, RIn | Exclude<RIn2, Scope.Scope>>RIn, function (type parameter) E in <RIn, E, ROut, XR extends ROut, RIn2, E2, X>(self: Layer<ROut, E, RIn>, f: (context: Context.Context<XR>) => Effect<X, E2, RIn2>): Layer<ROut, E | E2, RIn | Exclude<RIn2, Scope.Scope>>E, function (type parameter) ROut in <RIn, E, ROut, XR extends ROut, RIn2, E2, X>(self: Layer<ROut, E, RIn>, f: (context: Context.Context<XR>) => Effect<X, E2, RIn2>): Layer<ROut, E | E2, RIn | Exclude<RIn2, Scope.Scope>>ROut, function (type parameter) XR in <RIn, E, ROut, XR extends ROut, RIn2, E2, X>(self: Layer<ROut, E, RIn>, f: (context: Context.Context<XR>) => Effect<X, E2, RIn2>): Layer<ROut, E | E2, RIn | Exclude<RIn2, Scope.Scope>>XR extends function (type parameter) ROut in <RIn, E, ROut, XR extends ROut, RIn2, E2, X>(self: Layer<ROut, E, RIn>, f: (context: Context.Context<XR>) => Effect<X, E2, RIn2>): Layer<ROut, E | E2, RIn | Exclude<RIn2, Scope.Scope>>ROut, function (type parameter) RIn2 in <RIn, E, ROut, XR extends ROut, RIn2, E2, X>(self: Layer<ROut, E, RIn>, f: (context: Context.Context<XR>) => Effect<X, E2, RIn2>): Layer<ROut, E | E2, RIn | Exclude<RIn2, Scope.Scope>>RIn2, function (type parameter) E2 in <RIn, E, ROut, XR extends ROut, RIn2, E2, X>(self: Layer<ROut, E, RIn>, f: (context: Context.Context<XR>) => Effect<X, E2, RIn2>): Layer<ROut, E | E2, RIn | Exclude<RIn2, Scope.Scope>>E2, function (type parameter) X in <RIn, E, ROut, XR extends ROut, RIn2, E2, X>(self: Layer<ROut, E, RIn>, f: (context: Context.Context<XR>) => Effect<X, E2, RIn2>): Layer<ROut, E | E2, RIn | Exclude<RIn2, Scope.Scope>>X>(
self: Layer<ROut, E, RIn>(parameter) self: {
build: (memoMap: MemoMap, scope: Scope.Scope) => Effect<Context.Context<ROut>, E, RIn>;
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 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) ROut in <RIn, E, ROut, XR extends ROut, RIn2, E2, X>(self: Layer<ROut, E, RIn>, f: (context: Context.Context<XR>) => Effect<X, E2, RIn2>): Layer<ROut, E | E2, RIn | Exclude<RIn2, Scope.Scope>>ROut, function (type parameter) E in <RIn, E, ROut, XR extends ROut, RIn2, E2, X>(self: Layer<ROut, E, RIn>, f: (context: Context.Context<XR>) => Effect<X, E2, RIn2>): Layer<ROut, E | E2, RIn | Exclude<RIn2, Scope.Scope>>E, function (type parameter) RIn in <RIn, E, ROut, XR extends ROut, RIn2, E2, X>(self: Layer<ROut, E, RIn>, f: (context: Context.Context<XR>) => Effect<X, E2, RIn2>): Layer<ROut, E | E2, RIn | Exclude<RIn2, Scope.Scope>>RIn>,
f: (
context: Context.Context<XR>
) => Effect<X, E2, RIn2>
context: Context.Context<XR>(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 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) XR in <RIn, E, ROut, XR extends ROut, RIn2, E2, X>(self: Layer<ROut, E, RIn>, f: (context: Context.Context<XR>) => Effect<X, E2, RIn2>): Layer<ROut, E | E2, RIn | Exclude<RIn2, Scope.Scope>>XR>) => interface Effect<out A, out E = never, out R = never>The Effect interface defines a value that lazily describes a workflow or
job. The workflow requires some context R, and may fail with an error of
type E, or succeed with a value of type A.
When to use
Use when you need to represent a lazy, composable workflow that can require
services, fail with a typed error, or succeed with a typed value.
Details
Effect values model resourceful interaction with the outside world,
including synchronous, asynchronous, concurrent, and parallel interaction.
They use a fiber-based concurrency model, with built-in support for
scheduling, fine-grained interruption, structured concurrency, and high
scalability.
To run an Effect value, you need a Runtime, which is a type that is
capable of executing Effect values.
Effect<function (type parameter) X in <RIn, E, ROut, XR extends ROut, RIn2, E2, X>(self: Layer<ROut, E, RIn>, f: (context: Context.Context<XR>) => Effect<X, E2, RIn2>): Layer<ROut, E | E2, RIn | Exclude<RIn2, Scope.Scope>>X, function (type parameter) E2 in <RIn, E, ROut, XR extends ROut, RIn2, E2, X>(self: Layer<ROut, E, RIn>, f: (context: Context.Context<XR>) => Effect<X, E2, RIn2>): Layer<ROut, E | E2, RIn | Exclude<RIn2, Scope.Scope>>E2, function (type parameter) RIn2 in <RIn, E, ROut, XR extends ROut, RIn2, E2, X>(self: Layer<ROut, E, RIn>, f: (context: Context.Context<XR>) => Effect<X, E2, RIn2>): Layer<ROut, E | E2, RIn | Exclude<RIn2, Scope.Scope>>RIn2>
): 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) ROut in <RIn, E, ROut, XR extends ROut, RIn2, E2, X>(self: Layer<ROut, E, RIn>, f: (context: Context.Context<XR>) => Effect<X, E2, RIn2>): Layer<ROut, E | E2, RIn | Exclude<RIn2, Scope.Scope>>ROut, function (type parameter) E in <RIn, E, ROut, XR extends ROut, RIn2, E2, X>(self: Layer<ROut, E, RIn>, f: (context: Context.Context<XR>) => Effect<X, E2, RIn2>): Layer<ROut, E | E2, RIn | Exclude<RIn2, Scope.Scope>>E | function (type parameter) E2 in <RIn, E, ROut, XR extends ROut, RIn2, E2, X>(self: Layer<ROut, E, RIn>, f: (context: Context.Context<XR>) => Effect<X, E2, RIn2>): Layer<ROut, E | E2, RIn | Exclude<RIn2, Scope.Scope>>E2, function (type parameter) RIn in <RIn, E, ROut, XR extends ROut, RIn2, E2, X>(self: Layer<ROut, E, RIn>, f: (context: Context.Context<XR>) => Effect<X, E2, RIn2>): Layer<ROut, E | E2, RIn | Exclude<RIn2, Scope.Scope>>RIn | type Exclude<T, U> = T extends U
? never
: T
Exclude from T those types that are assignable to U
Exclude<function (type parameter) RIn2 in <RIn, E, ROut, XR extends ROut, RIn2, E2, X>(self: Layer<ROut, E, RIn>, f: (context: Context.Context<XR>) => Effect<X, E2, RIn2>): Layer<ROut, E | E2, RIn | Exclude<RIn2, Scope.Scope>>RIn2, import ScopeScope.Scope>>
} = dual<(...args: Array<any>) => any, <RIn, E, ROut, XR extends ROut, RIn2, E2, X>(self: Layer<ROut, E, RIn>, f: (context: Context.Context<XR>) => Effect<X, E2, RIn2>) => Layer<ROut, E | E2, RIn | Exclude<RIn2, Scope.Scope>>>(arity: 2, body: <RIn, E, ROut, XR extends ROut, RIn2, E2, X>(self: Layer<ROut, E, RIn>, f: (context: Context.Context<XR>) => Effect<X, E2, RIn2>) => Layer<ROut, E | E2, RIn | Exclude<RIn2, Scope.Scope>>): ((...args: Array<any>) => any) & (<RIn, E, ROut, XR extends ROut, RIn2, E2, X>(self: Layer<ROut, E, RIn>, f: (context: Context.Context<XR>) => Effect<X, E2, RIn2>) => Layer<ROut, E | E2, RIn | Exclude<RIn2, Scope.Scope>>) (+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(2, <function (type parameter) RIn in <RIn, E, ROut, XR extends ROut, RIn2, E2, X>(self: Layer<ROut, E, RIn>, f: (context: Context.Context<XR>) => Effect<X, E2, RIn2>): Layer<ROut, E | E2, RIn | Exclude<RIn2, Scope.Scope>>RIn, function (type parameter) E in <RIn, E, ROut, XR extends ROut, RIn2, E2, X>(self: Layer<ROut, E, RIn>, f: (context: Context.Context<XR>) => Effect<X, E2, RIn2>): Layer<ROut, E | E2, RIn | Exclude<RIn2, Scope.Scope>>E, function (type parameter) ROut in <RIn, E, ROut, XR extends ROut, RIn2, E2, X>(self: Layer<ROut, E, RIn>, f: (context: Context.Context<XR>) => Effect<X, E2, RIn2>): Layer<ROut, E | E2, RIn | Exclude<RIn2, Scope.Scope>>ROut, function (type parameter) XR in <RIn, E, ROut, XR extends ROut, RIn2, E2, X>(self: Layer<ROut, E, RIn>, f: (context: Context.Context<XR>) => Effect<X, E2, RIn2>): Layer<ROut, E | E2, RIn | Exclude<RIn2, Scope.Scope>>XR extends function (type parameter) ROut in <RIn, E, ROut, XR extends ROut, RIn2, E2, X>(self: Layer<ROut, E, RIn>, f: (context: Context.Context<XR>) => Effect<X, E2, RIn2>): Layer<ROut, E | E2, RIn | Exclude<RIn2, Scope.Scope>>ROut, function (type parameter) RIn2 in <RIn, E, ROut, XR extends ROut, RIn2, E2, X>(self: Layer<ROut, E, RIn>, f: (context: Context.Context<XR>) => Effect<X, E2, RIn2>): Layer<ROut, E | E2, RIn | Exclude<RIn2, Scope.Scope>>RIn2, function (type parameter) E2 in <RIn, E, ROut, XR extends ROut, RIn2, E2, X>(self: Layer<ROut, E, RIn>, f: (context: Context.Context<XR>) => Effect<X, E2, RIn2>): Layer<ROut, E | E2, RIn | Exclude<RIn2, Scope.Scope>>E2, function (type parameter) X in <RIn, E, ROut, XR extends ROut, RIn2, E2, X>(self: Layer<ROut, E, RIn>, f: (context: Context.Context<XR>) => Effect<X, E2, RIn2>): Layer<ROut, E | E2, RIn | Exclude<RIn2, Scope.Scope>>X>(
self: Layer<ROut, E, RIn>(parameter) self: {
build: (memoMap: MemoMap, scope: Scope.Scope) => Effect<Context.Context<ROut>, E, RIn>;
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 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) ROut in <RIn, E, ROut, XR extends ROut, RIn2, E2, X>(self: Layer<ROut, E, RIn>, f: (context: Context.Context<XR>) => Effect<X, E2, RIn2>): Layer<ROut, E | E2, RIn | Exclude<RIn2, Scope.Scope>>ROut, function (type parameter) E in <RIn, E, ROut, XR extends ROut, RIn2, E2, X>(self: Layer<ROut, E, RIn>, f: (context: Context.Context<XR>) => Effect<X, E2, RIn2>): Layer<ROut, E | E2, RIn | Exclude<RIn2, Scope.Scope>>E, function (type parameter) RIn in <RIn, E, ROut, XR extends ROut, RIn2, E2, X>(self: Layer<ROut, E, RIn>, f: (context: Context.Context<XR>) => Effect<X, E2, RIn2>): Layer<ROut, E | E2, RIn | Exclude<RIn2, Scope.Scope>>RIn>,
f: (
context: Context.Context<XR>
) => Effect<X, E2, RIn2>
context: Context.Context<XR>(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 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) XR in <RIn, E, ROut, XR extends ROut, RIn2, E2, X>(self: Layer<ROut, E, RIn>, f: (context: Context.Context<XR>) => Effect<X, E2, RIn2>): Layer<ROut, E | E2, RIn | Exclude<RIn2, Scope.Scope>>XR>) => interface Effect<out A, out E = never, out R = never>The Effect interface defines a value that lazily describes a workflow or
job. The workflow requires some context R, and may fail with an error of
type E, or succeed with a value of type A.
When to use
Use when you need to represent a lazy, composable workflow that can require
services, fail with a typed error, or succeed with a typed value.
Details
Effect values model resourceful interaction with the outside world,
including synchronous, asynchronous, concurrent, and parallel interaction.
They use a fiber-based concurrency model, with built-in support for
scheduling, fine-grained interruption, structured concurrency, and high
scalability.
To run an Effect value, you need a Runtime, which is a type that is
capable of executing Effect values.
Effect<function (type parameter) X in <RIn, E, ROut, XR extends ROut, RIn2, E2, X>(self: Layer<ROut, E, RIn>, f: (context: Context.Context<XR>) => Effect<X, E2, RIn2>): Layer<ROut, E | E2, RIn | Exclude<RIn2, Scope.Scope>>X, function (type parameter) E2 in <RIn, E, ROut, XR extends ROut, RIn2, E2, X>(self: Layer<ROut, E, RIn>, f: (context: Context.Context<XR>) => Effect<X, E2, RIn2>): Layer<ROut, E | E2, RIn | Exclude<RIn2, Scope.Scope>>E2, function (type parameter) RIn2 in <RIn, E, ROut, XR extends ROut, RIn2, E2, X>(self: Layer<ROut, E, RIn>, f: (context: Context.Context<XR>) => Effect<X, E2, RIn2>): Layer<ROut, E | E2, RIn | Exclude<RIn2, Scope.Scope>>RIn2>
): 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) ROut in <RIn, E, ROut, XR extends ROut, RIn2, E2, X>(self: Layer<ROut, E, RIn>, f: (context: Context.Context<XR>) => Effect<X, E2, RIn2>): Layer<ROut, E | E2, RIn | Exclude<RIn2, Scope.Scope>>ROut, function (type parameter) E in <RIn, E, ROut, XR extends ROut, RIn2, E2, X>(self: Layer<ROut, E, RIn>, f: (context: Context.Context<XR>) => Effect<X, E2, RIn2>): Layer<ROut, E | E2, RIn | Exclude<RIn2, Scope.Scope>>E | function (type parameter) E2 in <RIn, E, ROut, XR extends ROut, RIn2, E2, X>(self: Layer<ROut, E, RIn>, f: (context: Context.Context<XR>) => Effect<X, E2, RIn2>): Layer<ROut, E | E2, RIn | Exclude<RIn2, Scope.Scope>>E2, function (type parameter) RIn in <RIn, E, ROut, XR extends ROut, RIn2, E2, X>(self: Layer<ROut, E, RIn>, f: (context: Context.Context<XR>) => Effect<X, E2, RIn2>): Layer<ROut, E | E2, RIn | Exclude<RIn2, Scope.Scope>>RIn | type Exclude<T, U> = T extends U
? never
: T
Exclude from T those types that are assignable to U
Exclude<function (type parameter) RIn2 in <RIn, E, ROut, XR extends ROut, RIn2, E2, X>(self: Layer<ROut, E, RIn>, f: (context: Context.Context<XR>) => Effect<X, E2, RIn2>): Layer<ROut, E | E2, RIn | Exclude<RIn2, Scope.Scope>>RIn2, import ScopeScope.Scope>> =>
const fromBuild: <ROut, E, RIn>(
build: (
memoMap: MemoMap,
scope: Scope.Scope
) => Effect<Context.Context<ROut>, E, RIn>
) => Layer<ROut, E, RIn>
Constructs a Layer from a function that uses a MemoMap and Scope to
build the layer.
Details
The function receives a MemoMap for memoization and a Scope for resource management.
A child scope is created, and if the build fails, the child scope is closed.
Example (Constructing a layer from a build function)
import { Context, Effect, Layer } from "effect"
class Database extends Context.Service<Database, {
readonly query: (sql: string) => Effect.Effect<string>
}>()("Database") {}
const databaseLayer = Layer.fromBuild(() =>
Effect.sync(() =>
Context.make(Database, {
query: (sql: string) => Effect.succeed("result")
})
)
)
fromBuild((memoMap: MemoMap(parameter) memoMap: {
get: <RIn, E, ROut>(layer: Layer<ROut, E, RIn>, scope: Scope.Scope) => Effect<Context.Context<ROut>, E, RIn> | undefined;
getOrElseMemoize: <RIn, E, ROut>(layer: Layer<ROut, E, RIn>, scope: Scope.Scope, build: (memoMap: MemoMap, scope: Scope.Scope) => Effect<Context.Context<ROut>, E, RIn>) => Effect<Context.Context<ROut>, E, RIn>;
}
scope: Scope.Scope(parameter) scope: {
strategy: "sequential" | "parallel";
state: State.Open | State.Closed | State.Empty;
}
import internalEffectinternalEffect.const flatMap: {
<A, B, E2, R2>(
f: (a: A) => Effect.Effect<B, E2, R2>
): <E, R>(
self: Effect.Effect<A, E, R>
) => Effect.Effect<B, E | E2, R | R2>
<A, E, R, B, E2, R2>(
self: Effect.Effect<A, E, R>,
f: (a: A) => Effect.Effect<B, E2, R2>
): Effect.Effect<B, E | E2, R | R2>
}
self: Layer<ROut, E, RIn>(parameter) self: {
build: (memoMap: MemoMap, scope: Scope.Scope) => Effect<Context.Context<ROut>, E, RIn>;
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; <…;
}
function Layer(memoMap: MemoMap, scope: Scope.Scope): Effect<Context.Context<ROut>, E, RIn>build(memoMap: MemoMap(parameter) memoMap: {
get: <RIn, E, ROut>(layer: Layer<ROut, E, RIn>, scope: Scope.Scope) => Effect<Context.Context<ROut>, E, RIn> | undefined;
getOrElseMemoize: <RIn, E, ROut>(layer: Layer<ROut, E, RIn>, scope: Scope.Scope, build: (memoMap: MemoMap, scope: Scope.Scope) => Effect<Context.Context<ROut>, E, RIn>) => Effect<Context.Context<ROut>, E, RIn>;
}
scope: Scope.Scope(parameter) scope: {
strategy: "sequential" | "parallel";
state: State.Open | State.Closed | State.Empty;
}
context: Context.Context<ROut>(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 ScopeScope.const provide: {
(value: Scope): <A, E, R>(
self: Effect<A, E, R>
) => Effect<A, E, Exclude<R, Scope>>
<A, E, R>(
self: Effect<A, E, R>,
value: Scope
): Effect<A, E, Exclude<R, Scope>>
}
import internalEffectinternalEffect.const as: {
<A, B>(value: B): <E, R>(
self: Effect.Effect<A, E, R>
) => Effect.Effect<B, E, R>
<A, E, R, B>(
self: Effect.Effect<A, E, R>,
value: B
): Effect.Effect<B, E, R>
}
f: (
context: Context.Context<XR>
) => Effect<X, E2, RIn2>
context: Context.Context<ROut>(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 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) XR in <RIn, E, ROut, XR extends ROut, RIn2, E2, X>(self: Layer<ROut, E, RIn>, f: (context: Context.Context<XR>) => Effect<X, E2, RIn2>): Layer<ROut, E | E2, RIn | Exclude<RIn2, Scope.Scope>>XR>), context: Context.Context<ROut>(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;
}
scope: Scope.Scope(parameter) scope: {
strategy: "sequential" | "parallel";
state: State.Open | State.Closed | State.Empty;
}