<RIn, E, ROut>(that: Layer<ROut, E, RIn>): <RIn2, E2, ROut2>(
self: Layer<ROut2, E2, RIn2>
) => Layer<ROut | ROut2, E | E2, RIn | RIn2>
<const Layers extends [Any, ...Array<Any>]>(that: Layers): <A, E, R>(
self: Layer<A, E, R>
) => Layer<
A | Success<Layers[number]>,
E | Error<Layers[number]>,
Services<Layers[number]> | R
>
<RIn2, E2, ROut2, RIn, E, ROut>(
self: Layer<ROut2, E2, RIn2>,
that: Layer<ROut, E, RIn>
): Layer<ROut | ROut2, E | E2, RIn | RIn2>
<A, E, R, const Layers extends [Any, ...Array<Any>]>(
self: Layer<A, E, R>,
that: Layers
): Layer<
A | Success<Layers[number]>,
E | Error<Layers[number]>,
Services<Layers[number]> | R
>Merges this layer with another layer concurrently, producing a new layer with combined input, error, and output types.
When to use
Use to combine an existing Layer with another Layer or an array of
layers while preserving pipeline style.
Details
This is a binary version of mergeAll that merges exactly two layers or one
layer with an array of layers. The layers are built concurrently and their
outputs are combined.
Example (Merging two layers)
import { Context, Effect, Layer } from "effect"
class Database extends Context.Service<Database, {
readonly query: (sql: string) => Effect.Effect<string>
}>()("Database") {}
class Logger extends Context.Service<Logger, {
readonly log: (msg: string) => Effect.Effect<void>
}>()("Logger") {}
const dbLayer = Layer.succeed(Database, {
query: Effect.fn("Database.query")((sql: string) => Effect.succeed("result"))
})
const loggerLayer = Layer.succeed(Logger, {
log: Effect.fn("Logger.log")((msg: string) => Effect.sync(() => console.log(msg)))
})
const mergedLayer = Layer.merge(dbLayer, loggerLayer)export const const merge: {
<RIn, E, ROut>(that: Layer<ROut, E, RIn>): <
RIn2,
E2,
ROut2
>(
self: Layer<ROut2, E2, RIn2>
) => Layer<ROut | ROut2, E | E2, RIn | RIn2>
<Layers extends [Any, ...Array<Any>]>(
that: Layers
): <A, E, R>(
self: Layer<A, E, R>
) => Layer<
A | Success<Layers[number]>,
E | Error<Layers[number]>,
Services<Layers[number]> | R
>
<RIn2, E2, ROut2, RIn, E, ROut>(
self: Layer<ROut2, E2, RIn2>,
that: Layer<ROut, E, RIn>
): Layer<ROut | ROut2, E | E2, RIn | RIn2>
<A, E, R, Layers extends [Any, ...Array<Any>]>(
self: Layer<A, E, R>,
that: Layers
): Layer<
A | Success<Layers[number]>,
E | Error<Layers[number]>,
Services<Layers[number]> | R
>
}
Merges this layer with another layer concurrently, producing a new layer with
combined input, error, and output types.
When to use
Use to combine an existing Layer with another Layer or an array of
layers while preserving pipeline style.
Details
This is a binary version of mergeAll that merges exactly two layers or one
layer with an array of layers. The layers are built concurrently and their
outputs are combined.
Example (Merging two layers)
import { Context, Effect, Layer } from "effect"
class Database extends Context.Service<Database, {
readonly query: (sql: string) => Effect.Effect<string>
}>()("Database") {}
class Logger extends Context.Service<Logger, {
readonly log: (msg: string) => Effect.Effect<void>
}>()("Logger") {}
const dbLayer = Layer.succeed(Database, {
query: Effect.fn("Database.query")((sql: string) => Effect.succeed("result"))
})
const loggerLayer = Layer.succeed(Logger, {
log: Effect.fn("Logger.log")((msg: string) => Effect.sync(() => console.log(msg)))
})
const mergedLayer = Layer.merge(dbLayer, loggerLayer)
merge: {
<function (type parameter) RIn in <RIn, E, ROut>(that: Layer<ROut, E, RIn>): <RIn2, E2, ROut2>(self: Layer<ROut2, E2, RIn2>) => Layer<ROut | ROut2, E | E2, RIn | RIn2>RIn, function (type parameter) E in <RIn, E, ROut>(that: Layer<ROut, E, RIn>): <RIn2, E2, ROut2>(self: Layer<ROut2, E2, RIn2>) => Layer<ROut | ROut2, E | E2, RIn | RIn2>E, function (type parameter) ROut in <RIn, E, ROut>(that: Layer<ROut, E, RIn>): <RIn2, E2, ROut2>(self: Layer<ROut2, E2, RIn2>) => Layer<ROut | ROut2, E | E2, RIn | RIn2>ROut>(
that: Layer<ROut, E, RIn>(parameter) that: {
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>(that: Layer<ROut, E, RIn>): <RIn2, E2, ROut2>(self: Layer<ROut2, E2, RIn2>) => Layer<ROut | ROut2, E | E2, RIn | RIn2>ROut, function (type parameter) E in <RIn, E, ROut>(that: Layer<ROut, E, RIn>): <RIn2, E2, ROut2>(self: Layer<ROut2, E2, RIn2>) => Layer<ROut | ROut2, E | E2, RIn | RIn2>E, function (type parameter) RIn in <RIn, E, ROut>(that: Layer<ROut, E, RIn>): <RIn2, E2, ROut2>(self: Layer<ROut2, E2, RIn2>) => Layer<ROut | ROut2, E | E2, RIn | RIn2>RIn>
): <function (type parameter) RIn2 in <RIn2, E2, ROut2>(self: Layer<ROut2, E2, RIn2>): Layer<ROut | ROut2, E | E2, RIn | RIn2>RIn2, function (type parameter) E2 in <RIn2, E2, ROut2>(self: Layer<ROut2, E2, RIn2>): Layer<ROut | ROut2, E | E2, RIn | RIn2>E2, function (type parameter) ROut2 in <RIn2, E2, ROut2>(self: Layer<ROut2, E2, RIn2>): Layer<ROut | ROut2, E | E2, RIn | RIn2>ROut2>(self: Layer<ROut2, E2, RIn2>(parameter) self: {
build: (memoMap: MemoMap, scope: Scope.Scope) => Effect<Context.Context<ROut2>, E2, RIn2>;
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) ROut2 in <RIn2, E2, ROut2>(self: Layer<ROut2, E2, RIn2>): Layer<ROut | ROut2, E | E2, RIn | RIn2>ROut2, function (type parameter) E2 in <RIn2, E2, ROut2>(self: Layer<ROut2, E2, RIn2>): Layer<ROut | ROut2, E | E2, RIn | RIn2>E2, function (type parameter) RIn2 in <RIn2, E2, ROut2>(self: Layer<ROut2, E2, RIn2>): Layer<ROut | ROut2, E | E2, RIn | RIn2>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>(that: Layer<ROut, E, RIn>): <RIn2, E2, ROut2>(self: Layer<ROut2, E2, RIn2>) => Layer<ROut | ROut2, E | E2, RIn | RIn2>ROut | function (type parameter) ROut2 in <RIn2, E2, ROut2>(self: Layer<ROut2, E2, RIn2>): Layer<ROut | ROut2, E | E2, RIn | RIn2>ROut2, function (type parameter) E in <RIn, E, ROut>(that: Layer<ROut, E, RIn>): <RIn2, E2, ROut2>(self: Layer<ROut2, E2, RIn2>) => Layer<ROut | ROut2, E | E2, RIn | RIn2>E | function (type parameter) E2 in <RIn2, E2, ROut2>(self: Layer<ROut2, E2, RIn2>): Layer<ROut | ROut2, E | E2, RIn | RIn2>E2, function (type parameter) RIn in <RIn, E, ROut>(that: Layer<ROut, E, RIn>): <RIn2, E2, ROut2>(self: Layer<ROut2, E2, RIn2>) => Layer<ROut | ROut2, E | E2, RIn | RIn2>RIn | function (type parameter) RIn2 in <RIn2, E2, ROut2>(self: Layer<ROut2, E2, RIn2>): Layer<ROut | ROut2, E | E2, RIn | RIn2>RIn2>
<const function (type parameter) Layers in <const Layers extends [Any, ...Array<Any>]>(that: Layers): <A, E, R>(self: Layer<A, E, R>) => Layer<A | Success<Layers[number]>, E | Error<Layers[number]>, Services<Layers[number]> | R>Layers extends [Any, ...interface Array<T>Array<Any>]>(
that: const Layers extends [Any, ...Array<Any>]that: function (type parameter) Layers in <const Layers extends [Any, ...Array<Any>]>(that: Layers): <A, E, R>(self: Layer<A, E, R>) => Layer<A | Success<Layers[number]>, E | Error<Layers[number]>, Services<Layers[number]> | R>Layers
): <function (type parameter) A in <A, E, R>(self: Layer<A, E, R>): Layer<A | Success<Layers[number]>, E | Error<Layers[number]>, Services<Layers[number]> | R>A, function (type parameter) E in <A, E, R>(self: Layer<A, E, R>): Layer<A | Success<Layers[number]>, E | Error<Layers[number]>, Services<Layers[number]> | R>E, function (type parameter) R in <A, E, R>(self: Layer<A, E, R>): Layer<A | Success<Layers[number]>, E | Error<Layers[number]>, Services<Layers[number]> | R>R>(
self: Layer<A, E, R>(parameter) self: {
build: (memoMap: MemoMap, scope: Scope.Scope) => Effect<Context.Context<A>, E, R>;
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) A in <A, E, R>(self: Layer<A, E, R>): Layer<A | Success<Layers[number]>, E | Error<Layers[number]>, Services<Layers[number]> | R>A, function (type parameter) E in <A, E, R>(self: Layer<A, E, R>): Layer<A | Success<Layers[number]>, E | Error<Layers[number]>, Services<Layers[number]> | R>E, function (type parameter) R in <A, E, R>(self: Layer<A, E, R>): Layer<A | Success<Layers[number]>, E | Error<Layers[number]>, Services<Layers[number]> | R>R>
) => 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) A in <A, E, R>(self: Layer<A, E, R>): Layer<A | Success<Layers[number]>, E | Error<Layers[number]>, Services<Layers[number]> | R>A | type Success<T extends Any> =
T extends Layer<
infer _ROut,
infer _E,
infer _RIn
>
? _ROut
: never
Extracts the service output type (ROut) from a Layer type.
When to use
Use to derive the services provided by an existing or generic Layer without
restating its ROut type parameter.
Success<function (type parameter) Layers in <const Layers extends [Any, ...Array<Any>]>(that: Layers): <A, E, R>(self: Layer<A, E, R>) => Layer<A | Success<Layers[number]>, E | Error<Layers[number]>, Services<Layers[number]> | R>Layers[number]>,
function (type parameter) E in <A, E, R>(self: Layer<A, E, R>): Layer<A | Success<Layers[number]>, E | Error<Layers[number]>, Services<Layers[number]> | R>E | type Error<T extends Any> =
T extends Layer<
infer _ROut,
infer _E,
infer _RIn
>
? _E
: never
Extracts the error type (E) from a Layer type.
When to use
Use to derive a layer construction error type for helper types, wrappers, or
APIs that preserve a layer failure channel.
Error<function (type parameter) Layers in <const Layers extends [Any, ...Array<Any>]>(that: Layers): <A, E, R>(self: Layer<A, E, R>) => Layer<A | Success<Layers[number]>, E | Error<Layers[number]>, Services<Layers[number]> | R>Layers[number]>,
| type Services<T extends Any> =
T extends infer L
? L extends Layer<
infer _ROut,
infer _E,
infer _RIn
>
? _RIn
: never
: never
Extracts the service requirements (RIn) from a Layer type.
When to use
Use to derive the dependency requirements of a generic or inferred Layer
without restating its RIn type parameter.
Services<function (type parameter) Layers in <const Layers extends [Any, ...Array<Any>]>(that: Layers): <A, E, R>(self: Layer<A, E, R>) => Layer<A | Success<Layers[number]>, E | Error<Layers[number]>, Services<Layers[number]> | R>Layers[number]>
| function (type parameter) R in <A, E, R>(self: Layer<A, E, R>): Layer<A | Success<Layers[number]>, E | Error<Layers[number]>, Services<Layers[number]> | R>R
>
<function (type parameter) RIn2 in <RIn2, E2, ROut2, RIn, E, ROut>(self: Layer<ROut2, E2, RIn2>, that: Layer<ROut, E, RIn>): Layer<ROut | ROut2, E | E2, RIn | RIn2>RIn2, function (type parameter) E2 in <RIn2, E2, ROut2, RIn, E, ROut>(self: Layer<ROut2, E2, RIn2>, that: Layer<ROut, E, RIn>): Layer<ROut | ROut2, E | E2, RIn | RIn2>E2, function (type parameter) ROut2 in <RIn2, E2, ROut2, RIn, E, ROut>(self: Layer<ROut2, E2, RIn2>, that: Layer<ROut, E, RIn>): Layer<ROut | ROut2, E | E2, RIn | RIn2>ROut2, function (type parameter) RIn in <RIn2, E2, ROut2, RIn, E, ROut>(self: Layer<ROut2, E2, RIn2>, that: Layer<ROut, E, RIn>): Layer<ROut | ROut2, E | E2, RIn | RIn2>RIn, function (type parameter) E in <RIn2, E2, ROut2, RIn, E, ROut>(self: Layer<ROut2, E2, RIn2>, that: Layer<ROut, E, RIn>): Layer<ROut | ROut2, E | E2, RIn | RIn2>E, function (type parameter) ROut in <RIn2, E2, ROut2, RIn, E, ROut>(self: Layer<ROut2, E2, RIn2>, that: Layer<ROut, E, RIn>): Layer<ROut | ROut2, E | E2, RIn | RIn2>ROut>(
self: Layer<ROut2, E2, RIn2>(parameter) self: {
build: (memoMap: MemoMap, scope: Scope.Scope) => Effect<Context.Context<ROut2>, E2, RIn2>;
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) ROut2 in <RIn2, E2, ROut2, RIn, E, ROut>(self: Layer<ROut2, E2, RIn2>, that: Layer<ROut, E, RIn>): Layer<ROut | ROut2, E | E2, RIn | RIn2>ROut2, function (type parameter) E2 in <RIn2, E2, ROut2, RIn, E, ROut>(self: Layer<ROut2, E2, RIn2>, that: Layer<ROut, E, RIn>): Layer<ROut | ROut2, E | E2, RIn | RIn2>E2, function (type parameter) RIn2 in <RIn2, E2, ROut2, RIn, E, ROut>(self: Layer<ROut2, E2, RIn2>, that: Layer<ROut, E, RIn>): Layer<ROut | ROut2, E | E2, RIn | RIn2>RIn2>,
that: Layer<ROut, E, RIn>(parameter) that: {
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 <RIn2, E2, ROut2, RIn, E, ROut>(self: Layer<ROut2, E2, RIn2>, that: Layer<ROut, E, RIn>): Layer<ROut | ROut2, E | E2, RIn | RIn2>ROut, function (type parameter) E in <RIn2, E2, ROut2, RIn, E, ROut>(self: Layer<ROut2, E2, RIn2>, that: Layer<ROut, E, RIn>): Layer<ROut | ROut2, E | E2, RIn | RIn2>E, function (type parameter) RIn in <RIn2, E2, ROut2, RIn, E, ROut>(self: Layer<ROut2, E2, RIn2>, that: Layer<ROut, E, RIn>): Layer<ROut | ROut2, E | E2, RIn | RIn2>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 <RIn2, E2, ROut2, RIn, E, ROut>(self: Layer<ROut2, E2, RIn2>, that: Layer<ROut, E, RIn>): Layer<ROut | ROut2, E | E2, RIn | RIn2>ROut | function (type parameter) ROut2 in <RIn2, E2, ROut2, RIn, E, ROut>(self: Layer<ROut2, E2, RIn2>, that: Layer<ROut, E, RIn>): Layer<ROut | ROut2, E | E2, RIn | RIn2>ROut2, function (type parameter) E in <RIn2, E2, ROut2, RIn, E, ROut>(self: Layer<ROut2, E2, RIn2>, that: Layer<ROut, E, RIn>): Layer<ROut | ROut2, E | E2, RIn | RIn2>E | function (type parameter) E2 in <RIn2, E2, ROut2, RIn, E, ROut>(self: Layer<ROut2, E2, RIn2>, that: Layer<ROut, E, RIn>): Layer<ROut | ROut2, E | E2, RIn | RIn2>E2, function (type parameter) RIn in <RIn2, E2, ROut2, RIn, E, ROut>(self: Layer<ROut2, E2, RIn2>, that: Layer<ROut, E, RIn>): Layer<ROut | ROut2, E | E2, RIn | RIn2>RIn | function (type parameter) RIn2 in <RIn2, E2, ROut2, RIn, E, ROut>(self: Layer<ROut2, E2, RIn2>, that: Layer<ROut, E, RIn>): Layer<ROut | ROut2, E | E2, RIn | RIn2>RIn2>
<function (type parameter) A in <A, E, R, const Layers extends [Any, ...Array<Any>]>(self: Layer<A, E, R>, that: Layers): Layer<A | Success<Layers[number]>, E | Error<Layers[number]>, Services<Layers[number]> | R>A, function (type parameter) E in <A, E, R, const Layers extends [Any, ...Array<Any>]>(self: Layer<A, E, R>, that: Layers): Layer<A | Success<Layers[number]>, E | Error<Layers[number]>, Services<Layers[number]> | R>E, function (type parameter) R in <A, E, R, const Layers extends [Any, ...Array<Any>]>(self: Layer<A, E, R>, that: Layers): Layer<A | Success<Layers[number]>, E | Error<Layers[number]>, Services<Layers[number]> | R>R, const function (type parameter) Layers in <A, E, R, const Layers extends [Any, ...Array<Any>]>(self: Layer<A, E, R>, that: Layers): Layer<A | Success<Layers[number]>, E | Error<Layers[number]>, Services<Layers[number]> | R>Layers extends [Any, ...interface Array<T>Array<Any>]>(
self: Layer<A, E, R>(parameter) self: {
build: (memoMap: MemoMap, scope: Scope.Scope) => Effect<Context.Context<A>, E, R>;
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) A in <A, E, R, const Layers extends [Any, ...Array<Any>]>(self: Layer<A, E, R>, that: Layers): Layer<A | Success<Layers[number]>, E | Error<Layers[number]>, Services<Layers[number]> | R>A, function (type parameter) E in <A, E, R, const Layers extends [Any, ...Array<Any>]>(self: Layer<A, E, R>, that: Layers): Layer<A | Success<Layers[number]>, E | Error<Layers[number]>, Services<Layers[number]> | R>E, function (type parameter) R in <A, E, R, const Layers extends [Any, ...Array<Any>]>(self: Layer<A, E, R>, that: Layers): Layer<A | Success<Layers[number]>, E | Error<Layers[number]>, Services<Layers[number]> | R>R>,
that: const Layers extends [Any, ...Array<Any>]that: function (type parameter) Layers in <A, E, R, const Layers extends [Any, ...Array<Any>]>(self: Layer<A, E, R>, that: Layers): Layer<A | Success<Layers[number]>, E | Error<Layers[number]>, Services<Layers[number]> | R>Layers
): 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) A in <A, E, R, const Layers extends [Any, ...Array<Any>]>(self: Layer<A, E, R>, that: Layers): Layer<A | Success<Layers[number]>, E | Error<Layers[number]>, Services<Layers[number]> | R>A | type Success<T extends Any> =
T extends Layer<
infer _ROut,
infer _E,
infer _RIn
>
? _ROut
: never
Extracts the service output type (ROut) from a Layer type.
When to use
Use to derive the services provided by an existing or generic Layer without
restating its ROut type parameter.
Success<function (type parameter) Layers in <A, E, R, const Layers extends [Any, ...Array<Any>]>(self: Layer<A, E, R>, that: Layers): Layer<A | Success<Layers[number]>, E | Error<Layers[number]>, Services<Layers[number]> | R>Layers[number]>,
function (type parameter) E in <A, E, R, const Layers extends [Any, ...Array<Any>]>(self: Layer<A, E, R>, that: Layers): Layer<A | Success<Layers[number]>, E | Error<Layers[number]>, Services<Layers[number]> | R>E | type Error<T extends Any> =
T extends Layer<
infer _ROut,
infer _E,
infer _RIn
>
? _E
: never
Extracts the error type (E) from a Layer type.
When to use
Use to derive a layer construction error type for helper types, wrappers, or
APIs that preserve a layer failure channel.
Error<function (type parameter) Layers in <A, E, R, const Layers extends [Any, ...Array<Any>]>(self: Layer<A, E, R>, that: Layers): Layer<A | Success<Layers[number]>, E | Error<Layers[number]>, Services<Layers[number]> | R>Layers[number]>,
| type Services<T extends Any> =
T extends infer L
? L extends Layer<
infer _ROut,
infer _E,
infer _RIn
>
? _RIn
: never
: never
Extracts the service requirements (RIn) from a Layer type.
When to use
Use to derive the dependency requirements of a generic or inferred Layer
without restating its RIn type parameter.
Services<function (type parameter) Layers in <A, E, R, const Layers extends [Any, ...Array<Any>]>(self: Layer<A, E, R>, that: Layers): Layer<A | Success<Layers[number]>, E | Error<Layers[number]>, Services<Layers[number]> | R>Layers[number]>
| function (type parameter) R in <A, E, R, const Layers extends [Any, ...Array<Any>]>(self: Layer<A, E, R>, that: Layers): Layer<A | Success<Layers[number]>, E | Error<Layers[number]>, Services<Layers[number]> | R>R
>
} = import dualdual(2, (
self: Layer<any, any, any>(parameter) self: {
build: (memoMap: MemoMap, scope: Scope.Scope) => Effect<Context.Context<any>, any, any>;
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<any, any, any>,
that: | Layer<any, any, any>
| ReadonlyArray<Layer<any, any, any>>
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<any, any, any> | interface ReadonlyArray<T>ReadonlyArray<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<any, any, any>>
) => const mergeAll: <
Layers extends [
Layer<never, any, any>,
...Array<Layer<never, any, any>>
]
>(
...layers: Layers
) => Layer<
Success<Layers[number]>,
Error<Layers[number]>,
Services<Layers[number]>
>
Combines all the provided layers concurrently, creating a new layer with
merged input, error, and output types.
When to use
Use when you need to combine multiple independent layers.
Details
All layers are built concurrently, and their outputs are merged into a single layer.
If multiple merged layers depend on the same layer value, that dependency is
shared by default. Reuse a named layer value when you want services to share
the same resource, such as one database pool.
Example (Merging independent layers)
import { Context, Effect, Layer } from "effect"
class Database extends Context.Service<Database, {
readonly query: (sql: string) => Effect.Effect<string>
}>()("Database") {}
class Logger extends Context.Service<Logger, {
readonly log: (msg: string) => Effect.Effect<void>
}>()("Logger") {}
const dbLayer = Layer.succeed(Database, {
query: Effect.fn("Database.query")((sql: string) => Effect.succeed("result"))
})
const loggerLayer = Layer.succeed(Logger, {
log: Effect.fn("Logger.log")((msg: string) => Effect.sync(() => console.log(msg)))
})
const mergedLayer = Layer.mergeAll(dbLayer, loggerLayer)
mergeAll(self: Layer<any, any, any>(parameter) self: {
build: (memoMap: MemoMap, scope: Scope.Scope) => Effect<Context.Context<any>, any, any>;
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; <…;
}
var Array: ArrayConstructorArray.ArrayConstructor.isArray(arg: any): arg is any[]isArray(that: | Layer<any, any, any>
| ReadonlyArray<Layer<any, any, any>>
that: | Layer<any, any, any>
| ReadonlyArray<Layer<any, any, any>>
that: | Layer<any, any, any>
| ReadonlyArray<Layer<any, any, any>>