<ROut, EL, RL, A, E, R>(
dependency: Layer.Layer<ROut, EL, RL>,
resources: readonly [
Layer.Layer<A, E, R>,
...ReadonlyArray<Layer.Layer<A, E, R>>
]
): Layer.Layer<A, E | EL, Exclude<R, ROut> | RL>Provide one dependency Layer to several serve layers at once — sugar for
Layer.mergeAll(resources).pipe(Layer.provide(dependency)). Reads as "these resources, on this
dependency," so a group that shares an implementation states it once:
Hyperlink.provide(ImportHandlers.layer, [
Hyperlink.serve(SeasonMatches, seasonMatchesImpl),
Hyperlink.serve(LiveScorePoller, pollerImpl),
])It's plain Layer.provide underneath — no config-embedded layer — so sharing stays governed by
memoization (same dependency value → one instance; Layer.fresh to isolate).
Compose next to isolated serve layers in the same httpServer list when one resource needs a private dependency and the rest share theirs — that is the escape hatch for the old "rewrite the whole host off the bag API" cliff.
Source src/Hyperlink.ts:37495 lines
export const const provide: <ROut, EL, RL, A, E, R>(
dependency: Layer.Layer<ROut, EL, RL>,
resources: readonly [
Layer.Layer<A, E, R>,
...ReadonlyArray<Layer.Layer<A, E, R>>
]
) => Layer.Layer<A, E | EL, Exclude<R, ROut> | RL>
Provide one dependency Layer to several
serve
layers at once — sugar for
Layer.mergeAll(resources).pipe(Layer.provide(dependency)). Reads as "these resources, on this
dependency," so a group that shares an implementation states it once:
Hyperlink.provide(ImportHandlers.layer, [
Hyperlink.serve(SeasonMatches, seasonMatchesImpl),
Hyperlink.serve(LiveScorePoller, pollerImpl),
])
It's plain Layer.provide underneath — no config-embedded layer — so sharing stays governed by
memoization (same dependency value → one instance; Layer.fresh to isolate).
Compose next to isolated
serve
layers in the same
httpServer
list when one
resource needs a private dependency and the rest share theirs — that is the escape hatch for the
old "rewrite the whole host off the bag API" cliff.
provide = <function (type parameter) ROut in <ROut, EL, RL, A, E, R>(dependency: Layer.Layer<ROut, EL, RL>, resources: readonly [Layer.Layer<A, E, R>, ...ReadonlyArray<Layer.Layer<A, E, R>>]): Layer.Layer<A, E | EL, Exclude<R, ROut> | RL>ROut, function (type parameter) EL in <ROut, EL, RL, A, E, R>(dependency: Layer.Layer<ROut, EL, RL>, resources: readonly [Layer.Layer<A, E, R>, ...ReadonlyArray<Layer.Layer<A, E, R>>]): Layer.Layer<A, E | EL, Exclude<R, ROut> | RL>EL, function (type parameter) RL in <ROut, EL, RL, A, E, R>(dependency: Layer.Layer<ROut, EL, RL>, resources: readonly [Layer.Layer<A, E, R>, ...ReadonlyArray<Layer.Layer<A, E, R>>]): Layer.Layer<A, E | EL, Exclude<R, ROut> | RL>RL, function (type parameter) A in <ROut, EL, RL, A, E, R>(dependency: Layer.Layer<ROut, EL, RL>, resources: readonly [Layer.Layer<A, E, R>, ...ReadonlyArray<Layer.Layer<A, E, R>>]): Layer.Layer<A, E | EL, Exclude<R, ROut> | RL>A, function (type parameter) E in <ROut, EL, RL, A, E, R>(dependency: Layer.Layer<ROut, EL, RL>, resources: readonly [Layer.Layer<A, E, R>, ...ReadonlyArray<Layer.Layer<A, E, R>>]): Layer.Layer<A, E | EL, Exclude<R, ROut> | RL>E, function (type parameter) R in <ROut, EL, RL, A, E, R>(dependency: Layer.Layer<ROut, EL, RL>, resources: readonly [Layer.Layer<A, E, R>, ...ReadonlyArray<Layer.Layer<A, E, R>>]): Layer.Layer<A, E | EL, Exclude<R, ROut> | RL>R>(
dependency: Layer.Layer<ROut, EL, RL>(parameter) dependency: {
build: (memoMap: Layer.MemoMap, scope: Scope.Scope) => Effect.Effect<Context.Context<ROut>, EL, RL>;
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; <…;
}
import LayerLayer.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, EL, RL, A, E, R>(dependency: Layer.Layer<ROut, EL, RL>, resources: readonly [Layer.Layer<A, E, R>, ...ReadonlyArray<Layer.Layer<A, E, R>>]): Layer.Layer<A, E | EL, Exclude<R, ROut> | RL>ROut, function (type parameter) EL in <ROut, EL, RL, A, E, R>(dependency: Layer.Layer<ROut, EL, RL>, resources: readonly [Layer.Layer<A, E, R>, ...ReadonlyArray<Layer.Layer<A, E, R>>]): Layer.Layer<A, E | EL, Exclude<R, ROut> | RL>EL, function (type parameter) RL in <ROut, EL, RL, A, E, R>(dependency: Layer.Layer<ROut, EL, RL>, resources: readonly [Layer.Layer<A, E, R>, ...ReadonlyArray<Layer.Layer<A, E, R>>]): Layer.Layer<A, E | EL, Exclude<R, ROut> | RL>RL>,
resources: readonly [
Layer.Layer<A, E, R>,
...Layer.Layer<A, E, R>[]
]
(parameter) resources: {
0: Layer.Layer<A, E, R>;
length: number;
toString: () => string;
toLocaleString: { (): string; (locales: string | string[], options?: Intl.NumberFormatOptions & Intl.DateTimeFormatOptions): string };
concat: { (...items: Array<ConcatArray<Layer.Layer<A, E, R>>>): Array<Layer.Layer<A, E, R>>; (...items: Array<Layer.Layer<A, E, R> | ConcatArray<Layer.Layer<A, E, R>>>): Array<Layer.Layer<A, E, R>> };
join: (separator?: string) => string;
slice: (start?: number, end?: number) => Array<Layer.Layer<A, E, R>>;
indexOf: (searchElement: Layer.Layer<A, E, R>, fromIndex?: number) => number;
lastIndexOf: (searchElement: Layer.Layer<A, E, R>, fromIndex?: number) => number;
every: { (predicate: (value: Layer.Layer<A, E, R>, index: number, array: ReadonlyArray<Layer.Layer<A, E, R>>) => value is S, thisArg?: any): this is readonly S[]; (predicate: (value: Layer.Layer<A, E, R>, index: number, array: ReadonlyArray<Layer…;
some: (predicate: (value: Layer.Layer<A, E, R>, index: number, array: ReadonlyArray<Layer.Layer<A, E, R>>) => unknown, thisArg?: any) => boolean;
forEach: (callbackfn: (value: Layer.Layer<A, E, R>, index: number, array: ReadonlyArray<Layer.Layer<A, E, R>>) => void, thisArg?: any) => void;
map: (callbackfn: (value: Layer.Layer<A, E, R>, index: number, array: ReadonlyArray<Layer.Layer<A, E, R>>) => U, thisArg?: any) => Array<U>;
filter: { (predicate: (value: Layer.Layer<A, E, R>, index: number, array: ReadonlyArray<Layer.Layer<A, E, R>>) => value is S, thisArg?: any): Array<S>; (predicate: (value: Layer.Layer<A, E, R>, index: number, array: ReadonlyArray<Layer.Layer<A, E,…;
reduce: { (callbackfn: (previousValue: Layer.Layer<A, E, R>, currentValue: Layer.Layer<A, E, R>, currentIndex: number, array: ReadonlyArray<Layer.Layer<A, E, R>>) => Layer.Layer<A, E, R>): Layer.Layer<A, E, R>; (callbackfn: (previousValue: Layer.L…;
reduceRight: { (callbackfn: (previousValue: Layer.Layer<A, E, R>, currentValue: Layer.Layer<A, E, R>, currentIndex: number, array: ReadonlyArray<Layer.Layer<A, E, R>>) => Layer.Layer<A, E, R>): Layer.Layer<A, E, R>; (callbackfn: (previousValue: Layer.L…;
find: { (predicate: (value: Layer.Layer<A, E, R>, index: number, obj: ReadonlyArray<Layer.Layer<A, E, R>>) => value is S, thisArg?: any): S | undefined; (predicate: (value: Layer.Layer<A, E, R>, index: number, obj: ReadonlyArray<Layer.Layer<A, E…;
findIndex: (predicate: (value: Layer.Layer<A, E, R>, index: number, obj: ReadonlyArray<Layer.Layer<A, E, R>>) => unknown, thisArg?: any) => number;
entries: () => ArrayIterator<[number, Layer.Layer<A, E, R>]>;
keys: () => ArrayIterator<number>;
values: () => ArrayIterator<Layer.Layer<A, E, R>>;
includes: (searchElement: Layer.Layer<A, E, R>, fromIndex?: number) => boolean;
flatMap: (callback: (this: This, value: Layer.Layer<A, E, R>, index: number, array: Array<Layer.Layer<A, E, R>>) => U | ReadonlyArray<U>, thisArg?: This | undefined) => Array<U>;
flat: (this: A, depth?: D | undefined) => Array<FlatArray<A, D>>;
at: (index: number) => Layer.Layer<A, E, R> | undefined;
findLast: { (predicate: (value: Layer.Layer<A, E, R>, index: number, array: ReadonlyArray<Layer.Layer<A, E, R>>) => value is S, thisArg?: any): S | undefined; (predicate: (value: Layer.Layer<A, E, R>, index: number, array: ReadonlyArray<Layer.Layer<…;
findLastIndex: (predicate: (value: Layer.Layer<A, E, R>, index: number, array: ReadonlyArray<Layer.Layer<A, E, R>>) => unknown, thisArg?: any) => number;
toReversed: () => Array<Layer.Layer<A, E, R>>;
toSorted: (compareFn?: ((a: Layer.Layer<A, E, R>, b: Layer.Layer<A, E, R>) => number) | undefined) => Array<Layer.Layer<A, E, R>>;
toSpliced: { (start: number, deleteCount: number, ...items: Array<Layer.Layer<A, E, R>>): Array<Layer.Layer<A, E, R>>; (start: number, deleteCount?: number): Array<Layer.Layer<A, E, R>> };
with: (index: number, value: Layer.Layer<A, E, R>) => Array<Layer.Layer<A, E, R>>;
}
import LayerLayer.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 <ROut, EL, RL, A, E, R>(dependency: Layer.Layer<ROut, EL, RL>, resources: readonly [Layer.Layer<A, E, R>, ...ReadonlyArray<Layer.Layer<A, E, R>>]): Layer.Layer<A, E | EL, Exclude<R, ROut> | RL>A, function (type parameter) E in <ROut, EL, RL, A, E, R>(dependency: Layer.Layer<ROut, EL, RL>, resources: readonly [Layer.Layer<A, E, R>, ...ReadonlyArray<Layer.Layer<A, E, R>>]): Layer.Layer<A, E | EL, Exclude<R, ROut> | RL>E, function (type parameter) R in <ROut, EL, RL, A, E, R>(dependency: Layer.Layer<ROut, EL, RL>, resources: readonly [Layer.Layer<A, E, R>, ...ReadonlyArray<Layer.Layer<A, E, R>>]): Layer.Layer<A, E | EL, Exclude<R, ROut> | RL>R>, ...interface ReadonlyArray<T>ReadonlyArray<import LayerLayer.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 <ROut, EL, RL, A, E, R>(dependency: Layer.Layer<ROut, EL, RL>, resources: readonly [Layer.Layer<A, E, R>, ...ReadonlyArray<Layer.Layer<A, E, R>>]): Layer.Layer<A, E | EL, Exclude<R, ROut> | RL>A, function (type parameter) E in <ROut, EL, RL, A, E, R>(dependency: Layer.Layer<ROut, EL, RL>, resources: readonly [Layer.Layer<A, E, R>, ...ReadonlyArray<Layer.Layer<A, E, R>>]): Layer.Layer<A, E | EL, Exclude<R, ROut> | RL>E, function (type parameter) R in <ROut, EL, RL, A, E, R>(dependency: Layer.Layer<ROut, EL, RL>, resources: readonly [Layer.Layer<A, E, R>, ...ReadonlyArray<Layer.Layer<A, E, R>>]): Layer.Layer<A, E | EL, Exclude<R, ROut> | RL>R>>],
): import LayerLayer.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 <ROut, EL, RL, A, E, R>(dependency: Layer.Layer<ROut, EL, RL>, resources: readonly [Layer.Layer<A, E, R>, ...ReadonlyArray<Layer.Layer<A, E, R>>]): Layer.Layer<A, E | EL, Exclude<R, ROut> | RL>A, function (type parameter) E in <ROut, EL, RL, A, E, R>(dependency: Layer.Layer<ROut, EL, RL>, resources: readonly [Layer.Layer<A, E, R>, ...ReadonlyArray<Layer.Layer<A, E, R>>]): Layer.Layer<A, E | EL, Exclude<R, ROut> | RL>E | function (type parameter) EL in <ROut, EL, RL, A, E, R>(dependency: Layer.Layer<ROut, EL, RL>, resources: readonly [Layer.Layer<A, E, R>, ...ReadonlyArray<Layer.Layer<A, E, R>>]): Layer.Layer<A, E | EL, Exclude<R, ROut> | RL>EL, type Exclude<T, U> = T extends U
? never
: T
Exclude from T those types that are assignable to U
Exclude<function (type parameter) R in <ROut, EL, RL, A, E, R>(dependency: Layer.Layer<ROut, EL, RL>, resources: readonly [Layer.Layer<A, E, R>, ...ReadonlyArray<Layer.Layer<A, E, R>>]): Layer.Layer<A, E | EL, Exclude<R, ROut> | RL>R, function (type parameter) ROut in <ROut, EL, RL, A, E, R>(dependency: Layer.Layer<ROut, EL, RL>, resources: readonly [Layer.Layer<A, E, R>, ...ReadonlyArray<Layer.Layer<A, E, R>>]): Layer.Layer<A, E | EL, Exclude<R, ROut> | RL>ROut> | function (type parameter) RL in <ROut, EL, RL, A, E, R>(dependency: Layer.Layer<ROut, EL, RL>, resources: readonly [Layer.Layer<A, E, R>, ...ReadonlyArray<Layer.Layer<A, E, R>>]): Layer.Layer<A, E | EL, Exclude<R, ROut> | RL>RL> =>
import LayerLayer.const mergeAll: <[Layer.Layer<A, E, R>, ...Layer.Layer<A, E, R>[]]>(layers_0: Layer.Layer<A, E, R>, ...layers: Layer.Layer<A, E, R>[]) => Layer.Layer<A, E, R>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(...resources: readonly [
Layer.Layer<A, E, R>,
...Layer.Layer<A, E, R>[]
]
(parameter) resources: {
0: Layer.Layer<A, E, R>;
length: number;
toString: () => string;
toLocaleString: { (): string; (locales: string | string[], options?: Intl.NumberFormatOptions & Intl.DateTimeFormatOptions): string };
concat: { (...items: Array<ConcatArray<Layer.Layer<A, E, R>>>): Array<Layer.Layer<A, E, R>>; (...items: Array<Layer.Layer<A, E, R> | ConcatArray<Layer.Layer<A, E, R>>>): Array<Layer.Layer<A, E, R>> };
join: (separator?: string) => string;
slice: (start?: number, end?: number) => Array<Layer.Layer<A, E, R>>;
indexOf: (searchElement: Layer.Layer<A, E, R>, fromIndex?: number) => number;
lastIndexOf: (searchElement: Layer.Layer<A, E, R>, fromIndex?: number) => number;
every: { (predicate: (value: Layer.Layer<A, E, R>, index: number, array: ReadonlyArray<Layer.Layer<A, E, R>>) => value is S, thisArg?: any): this is readonly S[]; (predicate: (value: Layer.Layer<A, E, R>, index: number, array: ReadonlyArray<Layer…;
some: (predicate: (value: Layer.Layer<A, E, R>, index: number, array: ReadonlyArray<Layer.Layer<A, E, R>>) => unknown, thisArg?: any) => boolean;
forEach: (callbackfn: (value: Layer.Layer<A, E, R>, index: number, array: ReadonlyArray<Layer.Layer<A, E, R>>) => void, thisArg?: any) => void;
map: (callbackfn: (value: Layer.Layer<A, E, R>, index: number, array: ReadonlyArray<Layer.Layer<A, E, R>>) => U, thisArg?: any) => Array<U>;
filter: { (predicate: (value: Layer.Layer<A, E, R>, index: number, array: ReadonlyArray<Layer.Layer<A, E, R>>) => value is S, thisArg?: any): Array<S>; (predicate: (value: Layer.Layer<A, E, R>, index: number, array: ReadonlyArray<Layer.Layer<A, E,…;
reduce: { (callbackfn: (previousValue: Layer.Layer<A, E, R>, currentValue: Layer.Layer<A, E, R>, currentIndex: number, array: ReadonlyArray<Layer.Layer<A, E, R>>) => Layer.Layer<A, E, R>): Layer.Layer<A, E, R>; (callbackfn: (previousValue: Layer.L…;
reduceRight: { (callbackfn: (previousValue: Layer.Layer<A, E, R>, currentValue: Layer.Layer<A, E, R>, currentIndex: number, array: ReadonlyArray<Layer.Layer<A, E, R>>) => Layer.Layer<A, E, R>): Layer.Layer<A, E, R>; (callbackfn: (previousValue: Layer.L…;
find: { (predicate: (value: Layer.Layer<A, E, R>, index: number, obj: ReadonlyArray<Layer.Layer<A, E, R>>) => value is S, thisArg?: any): S | undefined; (predicate: (value: Layer.Layer<A, E, R>, index: number, obj: ReadonlyArray<Layer.Layer<A, E…;
findIndex: (predicate: (value: Layer.Layer<A, E, R>, index: number, obj: ReadonlyArray<Layer.Layer<A, E, R>>) => unknown, thisArg?: any) => number;
entries: () => ArrayIterator<[number, Layer.Layer<A, E, R>]>;
keys: () => ArrayIterator<number>;
values: () => ArrayIterator<Layer.Layer<A, E, R>>;
includes: (searchElement: Layer.Layer<A, E, R>, fromIndex?: number) => boolean;
flatMap: (callback: (this: This, value: Layer.Layer<A, E, R>, index: number, array: Array<Layer.Layer<A, E, R>>) => U | ReadonlyArray<U>, thisArg?: This | undefined) => Array<U>;
flat: (this: A, depth?: D | undefined) => Array<FlatArray<A, D>>;
at: (index: number) => Layer.Layer<A, E, R> | undefined;
findLast: { (predicate: (value: Layer.Layer<A, E, R>, index: number, array: ReadonlyArray<Layer.Layer<A, E, R>>) => value is S, thisArg?: any): S | undefined; (predicate: (value: Layer.Layer<A, E, R>, index: number, array: ReadonlyArray<Layer.Layer<…;
findLastIndex: (predicate: (value: Layer.Layer<A, E, R>, index: number, array: ReadonlyArray<Layer.Layer<A, E, R>>) => unknown, thisArg?: any) => number;
toReversed: () => Array<Layer.Layer<A, E, R>>;
toSorted: (compareFn?: ((a: Layer.Layer<A, E, R>, b: Layer.Layer<A, E, R>) => number) | undefined) => Array<Layer.Layer<A, E, R>>;
toSpliced: { (start: number, deleteCount: number, ...items: Array<Layer.Layer<A, E, R>>): Array<Layer.Layer<A, E, R>>; (start: number, deleteCount?: number): Array<Layer.Layer<A, E, R>> };
with: (index: number, value: Layer.Layer<A, E, R>) => Array<Layer.Layer<A, E, R>>;
}
Pipeable.pipe<Layer.Layer<A, E, R>, Layer.Layer<A, EL | E, RL | Exclude<R, ROut>>>(this: Layer.Layer<A, E, R>, ab: (_: Layer.Layer<A, E, R>) => Layer.Layer<A, EL | E, RL | Exclude<R, ROut>>): Layer.Layer<A, EL | E, RL | Exclude<R, ROut>> (+21 overloads)pipe(import LayerLayer.const provide: <RL, EL, ROut>(that: Layer.Layer<ROut, EL, RL>) => <RIn2, E2, ROut2>(self: Layer.Layer<ROut2, E2, RIn2>) => Layer.Layer<ROut2, EL | E2, RL | Exclude<RIn2, ROut>> (+3 overloads)Feeds the output services of the dependency layer into the requirements of
this layer, returning a layer that only provides the services from this layer.
When to use
Use when you need to hide an implementation dependency layer from callers.
Details
In serviceLayer.pipe(Layer.provide(dependencyLayer)), the dependency layer is
built first and is used to satisfy the requirements of serviceLayer.
Example (Providing layer dependencies)
import { Context, Effect, Layer } from "effect"
class Database extends Context.Service<Database, {
readonly query: (sql: string) => Effect.Effect<string>
}>()("Database") {}
class UserService extends Context.Service<UserService, {
readonly getUser: (id: string) => Effect.Effect<{
id: string
name: string
}>
}>()("UserService") {}
class Logger extends Context.Service<Logger, {
readonly log: (msg: string) => Effect.Effect<void>
}>()("Logger") {}
// Create dependency layers
const databaseLayer = Layer.succeed(Database, {
query: Effect.fn("Database.query")((sql: string) => Effect.succeed(`DB: ${sql}`))
})
const loggerLayer = Layer.succeed(Logger, {
log: Effect.fn("Logger.log")((msg: string) => Effect.sync(() => console.log(`[LOG] ${msg}`)))
})
// UserService depends on Database and Logger
const userServiceLayer = Layer.effect(UserService, Effect.gen(function*() {
const database = yield* Database
const logger = yield* Logger
return {
getUser: Effect.fn("UserService.getUser")(function*(id: string) {
yield* logger.log(`Looking up user ${id}`)
const result = yield* database.query(
`SELECT * FROM users WHERE id = ${id}`
)
return { id, name: result }
})
}
}))
// Provide dependencies to UserService layer
const userServiceWithDependencies = userServiceLayer.pipe(
Layer.provide(Layer.mergeAll(databaseLayer, loggerLayer))
)
// Now UserService layer has no dependencies
const program = Effect.gen(function*() {
const userService = yield* UserService
return yield* userService.getUser("123")
}).pipe(
Effect.provide(userServiceWithDependencies)
)
provide(dependency: Layer.Layer<ROut, EL, RL>(parameter) dependency: {
build: (memoMap: Layer.MemoMap, scope: Scope.Scope) => Effect.Effect<Context.Context<ROut>, EL, RL>;
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; <…;
}