<E, XE extends E, RIn2, E2, X>(f: (e: XE) => Effect<X, E2, RIn2>): <
RIn,
ROut
>(
self: Layer<ROut, E, RIn>
) => Layer<ROut, E | E2, RIn | Exclude<RIn2, Scope.Scope>>
<RIn, E, XE extends E, ROut, RIn2, E2, X>(
self: Layer<ROut, E, RIn>,
f: (e: XE) => Effect<X, E2, RIn2>
): Layer<ROut, E | E2, RIn | Exclude<RIn2, Scope.Scope>>Performs the specified effect if this layer fails.
When to use
Use to run logging, metrics, or other effects when layer construction fails while preserving the original typed error.
Details
The callback receives the typed error. If the callback succeeds, the layer still fails with the original error; if the callback fails, that failure is added to the layer's error type.
export const const tapError: {
<E, XE extends E, RIn2, E2, X>(
f: (e: XE) => Effect<X, E2, RIn2>
): <RIn, ROut>(
self: Layer<ROut, E, RIn>
) => Layer<
ROut,
E | E2,
RIn | Exclude<RIn2, Scope.Scope>
>
<RIn, E, XE extends E, ROut, RIn2, E2, X>(
self: Layer<ROut, E, RIn>,
f: (e: XE) => Effect<X, E2, RIn2>
): Layer<
ROut,
E | E2,
RIn | Exclude<RIn2, Scope.Scope>
>
}
Performs the specified effect if this layer fails.
When to use
Use to run logging, metrics, or other effects when layer construction fails
while preserving the original typed error.
Details
The callback receives the typed error. If the callback succeeds, the layer
still fails with the original error; if the callback fails, that failure is
added to the layer's error type.
tapError: {
<function (type parameter) E in <E, XE extends E, RIn2, E2, X>(f: (e: XE) => Effect<X, E2, RIn2>): <RIn, ROut>(self: Layer<ROut, E, RIn>) => Layer<ROut, E | E2, RIn | Exclude<RIn2, Scope.Scope>>E, function (type parameter) XE in <E, XE extends E, RIn2, E2, X>(f: (e: XE) => Effect<X, E2, RIn2>): <RIn, ROut>(self: Layer<ROut, E, RIn>) => Layer<ROut, E | E2, RIn | Exclude<RIn2, Scope.Scope>>XE extends function (type parameter) E in <E, XE extends E, RIn2, E2, X>(f: (e: XE) => Effect<X, E2, RIn2>): <RIn, ROut>(self: Layer<ROut, E, RIn>) => Layer<ROut, E | E2, RIn | Exclude<RIn2, Scope.Scope>>E, function (type parameter) RIn2 in <E, XE extends E, RIn2, E2, X>(f: (e: XE) => Effect<X, E2, RIn2>): <RIn, ROut>(self: Layer<ROut, E, RIn>) => Layer<ROut, E | E2, RIn | Exclude<RIn2, Scope.Scope>>RIn2, function (type parameter) E2 in <E, XE extends E, RIn2, E2, X>(f: (e: XE) => Effect<X, E2, RIn2>): <RIn, ROut>(self: Layer<ROut, E, RIn>) => Layer<ROut, E | E2, RIn | Exclude<RIn2, Scope.Scope>>E2, function (type parameter) X in <E, XE extends E, RIn2, E2, X>(f: (e: XE) => Effect<X, E2, RIn2>): <RIn, ROut>(self: Layer<ROut, E, RIn>) => Layer<ROut, E | E2, RIn | Exclude<RIn2, Scope.Scope>>X>(
f: (e: XE) => Effect<X, E2, RIn2>f: (e: XE extends Ee: function (type parameter) XE in <E, XE extends E, RIn2, E2, X>(f: (e: XE) => Effect<X, E2, RIn2>): <RIn, ROut>(self: Layer<ROut, E, RIn>) => Layer<ROut, E | E2, RIn | Exclude<RIn2, Scope.Scope>>XE) => 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 <E, XE extends E, RIn2, E2, X>(f: (e: XE) => Effect<X, E2, RIn2>): <RIn, ROut>(self: Layer<ROut, E, RIn>) => Layer<ROut, E | E2, RIn | Exclude<RIn2, Scope.Scope>>X, function (type parameter) E2 in <E, XE extends E, RIn2, E2, X>(f: (e: XE) => Effect<X, E2, RIn2>): <RIn, ROut>(self: Layer<ROut, E, RIn>) => Layer<ROut, E | E2, RIn | Exclude<RIn2, Scope.Scope>>E2, function (type parameter) RIn2 in <E, XE extends E, RIn2, E2, X>(f: (e: XE) => Effect<X, E2, RIn2>): <RIn, ROut>(self: Layer<ROut, E, RIn>) => Layer<ROut, E | E2, RIn | Exclude<RIn2, Scope.Scope>>RIn2>
): <function (type parameter) RIn in <RIn, ROut>(self: Layer<ROut, E, RIn>): Layer<ROut, E | E2, RIn | Exclude<RIn2, Scope.Scope>>RIn, function (type parameter) ROut in <RIn, ROut>(self: Layer<ROut, E, RIn>): Layer<ROut, E | E2, RIn | Exclude<RIn2, Scope.Scope>>ROut>(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, ROut>(self: Layer<ROut, E, RIn>): Layer<ROut, E | E2, RIn | Exclude<RIn2, Scope.Scope>>ROut, function (type parameter) E in <E, XE extends E, RIn2, E2, X>(f: (e: XE) => Effect<X, E2, RIn2>): <RIn, ROut>(self: Layer<ROut, E, RIn>) => Layer<ROut, E | E2, RIn | Exclude<RIn2, Scope.Scope>>E, function (type parameter) RIn in <RIn, ROut>(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 <RIn, ROut>(self: Layer<ROut, E, RIn>): Layer<ROut, E | E2, RIn | Exclude<RIn2, Scope.Scope>>ROut, function (type parameter) E in <E, XE extends E, RIn2, E2, X>(f: (e: XE) => Effect<X, E2, RIn2>): <RIn, ROut>(self: Layer<ROut, E, RIn>) => Layer<ROut, E | E2, RIn | Exclude<RIn2, Scope.Scope>>E | function (type parameter) E2 in <E, XE extends E, RIn2, E2, X>(f: (e: XE) => Effect<X, E2, RIn2>): <RIn, ROut>(self: Layer<ROut, E, RIn>) => Layer<ROut, E | E2, RIn | Exclude<RIn2, Scope.Scope>>E2, function (type parameter) RIn in <RIn, ROut>(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 <E, XE extends E, RIn2, E2, X>(f: (e: XE) => Effect<X, E2, RIn2>): <RIn, ROut>(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, XE extends E, ROut, RIn2, E2, X>(self: Layer<ROut, E, RIn>, f: (e: XE) => Effect<X, E2, RIn2>): Layer<ROut, E | E2, RIn | Exclude<RIn2, Scope.Scope>>RIn, function (type parameter) E in <RIn, E, XE extends E, ROut, RIn2, E2, X>(self: Layer<ROut, E, RIn>, f: (e: XE) => Effect<X, E2, RIn2>): Layer<ROut, E | E2, RIn | Exclude<RIn2, Scope.Scope>>E, function (type parameter) XE in <RIn, E, XE extends E, ROut, RIn2, E2, X>(self: Layer<ROut, E, RIn>, f: (e: XE) => Effect<X, E2, RIn2>): Layer<ROut, E | E2, RIn | Exclude<RIn2, Scope.Scope>>XE extends function (type parameter) E in <RIn, E, XE extends E, ROut, RIn2, E2, X>(self: Layer<ROut, E, RIn>, f: (e: XE) => Effect<X, E2, RIn2>): Layer<ROut, E | E2, RIn | Exclude<RIn2, Scope.Scope>>E, function (type parameter) ROut in <RIn, E, XE extends E, ROut, RIn2, E2, X>(self: Layer<ROut, E, RIn>, f: (e: XE) => Effect<X, E2, RIn2>): Layer<ROut, E | E2, RIn | Exclude<RIn2, Scope.Scope>>ROut, function (type parameter) RIn2 in <RIn, E, XE extends E, ROut, RIn2, E2, X>(self: Layer<ROut, E, RIn>, f: (e: XE) => Effect<X, E2, RIn2>): Layer<ROut, E | E2, RIn | Exclude<RIn2, Scope.Scope>>RIn2, function (type parameter) E2 in <RIn, E, XE extends E, ROut, RIn2, E2, X>(self: Layer<ROut, E, RIn>, f: (e: XE) => Effect<X, E2, RIn2>): Layer<ROut, E | E2, RIn | Exclude<RIn2, Scope.Scope>>E2, function (type parameter) X in <RIn, E, XE extends E, ROut, RIn2, E2, X>(self: Layer<ROut, E, RIn>, f: (e: XE) => 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, XE extends E, ROut, RIn2, E2, X>(self: Layer<ROut, E, RIn>, f: (e: XE) => Effect<X, E2, RIn2>): Layer<ROut, E | E2, RIn | Exclude<RIn2, Scope.Scope>>ROut, function (type parameter) E in <RIn, E, XE extends E, ROut, RIn2, E2, X>(self: Layer<ROut, E, RIn>, f: (e: XE) => Effect<X, E2, RIn2>): Layer<ROut, E | E2, RIn | Exclude<RIn2, Scope.Scope>>E, function (type parameter) RIn in <RIn, E, XE extends E, ROut, RIn2, E2, X>(self: Layer<ROut, E, RIn>, f: (e: XE) => Effect<X, E2, RIn2>): Layer<ROut, E | E2, RIn | Exclude<RIn2, Scope.Scope>>RIn>,
f: (e: XE) => Effect<X, E2, RIn2>f: (e: XE extends Ee: function (type parameter) XE in <RIn, E, XE extends E, ROut, RIn2, E2, X>(self: Layer<ROut, E, RIn>, f: (e: XE) => Effect<X, E2, RIn2>): Layer<ROut, E | E2, RIn | Exclude<RIn2, Scope.Scope>>XE) => 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, XE extends E, ROut, RIn2, E2, X>(self: Layer<ROut, E, RIn>, f: (e: XE) => Effect<X, E2, RIn2>): Layer<ROut, E | E2, RIn | Exclude<RIn2, Scope.Scope>>X, function (type parameter) E2 in <RIn, E, XE extends E, ROut, RIn2, E2, X>(self: Layer<ROut, E, RIn>, f: (e: XE) => Effect<X, E2, RIn2>): Layer<ROut, E | E2, RIn | Exclude<RIn2, Scope.Scope>>E2, function (type parameter) RIn2 in <RIn, E, XE extends E, ROut, RIn2, E2, X>(self: Layer<ROut, E, RIn>, f: (e: XE) => 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, XE extends E, ROut, RIn2, E2, X>(self: Layer<ROut, E, RIn>, f: (e: XE) => Effect<X, E2, RIn2>): Layer<ROut, E | E2, RIn | Exclude<RIn2, Scope.Scope>>ROut, function (type parameter) E in <RIn, E, XE extends E, ROut, RIn2, E2, X>(self: Layer<ROut, E, RIn>, f: (e: XE) => Effect<X, E2, RIn2>): Layer<ROut, E | E2, RIn | Exclude<RIn2, Scope.Scope>>E | function (type parameter) E2 in <RIn, E, XE extends E, ROut, RIn2, E2, X>(self: Layer<ROut, E, RIn>, f: (e: XE) => Effect<X, E2, RIn2>): Layer<ROut, E | E2, RIn | Exclude<RIn2, Scope.Scope>>E2, function (type parameter) RIn in <RIn, E, XE extends E, ROut, RIn2, E2, X>(self: Layer<ROut, E, RIn>, f: (e: XE) => 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, XE extends E, ROut, RIn2, E2, X>(self: Layer<ROut, E, RIn>, f: (e: XE) => Effect<X, E2, RIn2>): Layer<ROut, E | E2, RIn | Exclude<RIn2, Scope.Scope>>RIn2, import ScopeScope.Scope>>
} = dual<(...args: Array<any>) => any, <RIn, E, XE extends E, ROut, RIn2, E2, X>(self: Layer<ROut, E, RIn>, f: (e: XE) => Effect<X, E2, RIn2>) => Layer<ROut, E | E2, RIn | Exclude<RIn2, Scope.Scope>>>(arity: 2, body: <RIn, E, XE extends E, ROut, RIn2, E2, X>(self: Layer<ROut, E, RIn>, f: (e: XE) => Effect<X, E2, RIn2>) => Layer<ROut, E | E2, RIn | Exclude<RIn2, Scope.Scope>>): ((...args: Array<any>) => any) & (<RIn, E, XE extends E, ROut, RIn2, E2, X>(self: Layer<ROut, E, RIn>, f: (e: XE) => 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, XE extends E, ROut, RIn2, E2, X>(self: Layer<ROut, E, RIn>, f: (e: XE) => Effect<X, E2, RIn2>): Layer<ROut, E | E2, RIn | Exclude<RIn2, Scope.Scope>>RIn, function (type parameter) E in <RIn, E, XE extends E, ROut, RIn2, E2, X>(self: Layer<ROut, E, RIn>, f: (e: XE) => Effect<X, E2, RIn2>): Layer<ROut, E | E2, RIn | Exclude<RIn2, Scope.Scope>>E, function (type parameter) XE in <RIn, E, XE extends E, ROut, RIn2, E2, X>(self: Layer<ROut, E, RIn>, f: (e: XE) => Effect<X, E2, RIn2>): Layer<ROut, E | E2, RIn | Exclude<RIn2, Scope.Scope>>XE extends function (type parameter) E in <RIn, E, XE extends E, ROut, RIn2, E2, X>(self: Layer<ROut, E, RIn>, f: (e: XE) => Effect<X, E2, RIn2>): Layer<ROut, E | E2, RIn | Exclude<RIn2, Scope.Scope>>E, function (type parameter) ROut in <RIn, E, XE extends E, ROut, RIn2, E2, X>(self: Layer<ROut, E, RIn>, f: (e: XE) => Effect<X, E2, RIn2>): Layer<ROut, E | E2, RIn | Exclude<RIn2, Scope.Scope>>ROut, function (type parameter) RIn2 in <RIn, E, XE extends E, ROut, RIn2, E2, X>(self: Layer<ROut, E, RIn>, f: (e: XE) => Effect<X, E2, RIn2>): Layer<ROut, E | E2, RIn | Exclude<RIn2, Scope.Scope>>RIn2, function (type parameter) E2 in <RIn, E, XE extends E, ROut, RIn2, E2, X>(self: Layer<ROut, E, RIn>, f: (e: XE) => Effect<X, E2, RIn2>): Layer<ROut, E | E2, RIn | Exclude<RIn2, Scope.Scope>>E2, function (type parameter) X in <RIn, E, XE extends E, ROut, RIn2, E2, X>(self: Layer<ROut, E, RIn>, f: (e: XE) => 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, XE extends E, ROut, RIn2, E2, X>(self: Layer<ROut, E, RIn>, f: (e: XE) => Effect<X, E2, RIn2>): Layer<ROut, E | E2, RIn | Exclude<RIn2, Scope.Scope>>ROut, function (type parameter) E in <RIn, E, XE extends E, ROut, RIn2, E2, X>(self: Layer<ROut, E, RIn>, f: (e: XE) => Effect<X, E2, RIn2>): Layer<ROut, E | E2, RIn | Exclude<RIn2, Scope.Scope>>E, function (type parameter) RIn in <RIn, E, XE extends E, ROut, RIn2, E2, X>(self: Layer<ROut, E, RIn>, f: (e: XE) => Effect<X, E2, RIn2>): Layer<ROut, E | E2, RIn | Exclude<RIn2, Scope.Scope>>RIn>,
f: (e: XE) => Effect<X, E2, RIn2>f: (e: XE extends Ee: function (type parameter) XE in <RIn, E, XE extends E, ROut, RIn2, E2, X>(self: Layer<ROut, E, RIn>, f: (e: XE) => Effect<X, E2, RIn2>): Layer<ROut, E | E2, RIn | Exclude<RIn2, Scope.Scope>>XE) => 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, XE extends E, ROut, RIn2, E2, X>(self: Layer<ROut, E, RIn>, f: (e: XE) => Effect<X, E2, RIn2>): Layer<ROut, E | E2, RIn | Exclude<RIn2, Scope.Scope>>X, function (type parameter) E2 in <RIn, E, XE extends E, ROut, RIn2, E2, X>(self: Layer<ROut, E, RIn>, f: (e: XE) => Effect<X, E2, RIn2>): Layer<ROut, E | E2, RIn | Exclude<RIn2, Scope.Scope>>E2, function (type parameter) RIn2 in <RIn, E, XE extends E, ROut, RIn2, E2, X>(self: Layer<ROut, E, RIn>, f: (e: XE) => 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, XE extends E, ROut, RIn2, E2, X>(self: Layer<ROut, E, RIn>, f: (e: XE) => Effect<X, E2, RIn2>): Layer<ROut, E | E2, RIn | Exclude<RIn2, Scope.Scope>>ROut, function (type parameter) E in <RIn, E, XE extends E, ROut, RIn2, E2, X>(self: Layer<ROut, E, RIn>, f: (e: XE) => Effect<X, E2, RIn2>): Layer<ROut, E | E2, RIn | Exclude<RIn2, Scope.Scope>>E | function (type parameter) E2 in <RIn, E, XE extends E, ROut, RIn2, E2, X>(self: Layer<ROut, E, RIn>, f: (e: XE) => Effect<X, E2, RIn2>): Layer<ROut, E | E2, RIn | Exclude<RIn2, Scope.Scope>>E2, function (type parameter) RIn in <RIn, E, XE extends E, ROut, RIn2, E2, X>(self: Layer<ROut, E, RIn>, f: (e: XE) => 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, XE extends E, ROut, RIn2, E2, X>(self: Layer<ROut, E, RIn>, f: (e: XE) => 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 catch_: {
<E, B, E2, R2>(
f: (e: NoInfer<E>) => Effect.Effect<B, E2, R2>
): <A, R>(
self: Effect.Effect<A, E, R>
) => Effect.Effect<A | B, E2, R | R2>
<A, E, R, B, E2, R2>(
self: Effect.Effect<A, E, R>,
f: (e: NoInfer<E>) => Effect.Effect<B, E2, R2>
): Effect.Effect<A | B, 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;
}
error: Types.NoInfer<E>error) => 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 andThen: {
<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>
<B, E2, R2>(f: Effect.Effect<B, E2, R2>): <
A,
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>
<A, E, R, B, E2, R2>(
self: Effect.Effect<A, E, R>,
f: Effect.Effect<B, E2, R2>
): Effect.Effect<B, E | E2, R | R2>
}
f: (e: XE) => Effect<X, E2, RIn2>f(error: Types.NoInfer<E>error as function (type parameter) XE in <RIn, E, XE extends E, ROut, RIn2, E2, X>(self: Layer<ROut, E, RIn>, f: (e: XE) => Effect<X, E2, RIn2>): Layer<ROut, E | E2, RIn | Exclude<RIn2, Scope.Scope>>XE), import internalEffectinternalEffect.const fail: <E>(
error: E
) => Effect.Effect<never, E>
error: Types.NoInfer<E>error)), scope: Scope.Scope(parameter) scope: {
strategy: "sequential" | "parallel";
state: State.Open | State.Closed | State.Empty;
}