<A, E, R>(effect: Effect<Context.Context<A>, E, R>): Layer<
A,
E,
Exclude<R, Scope.Scope>
>Constructs a layer from an effect that produces all services in a Context.
When to use
Use when you need a Layer that effectfully constructs a Context with
multiple services.
Details
This allows you to create a Layer from an effectful computation that
returns multiple services. The Effect is executed in the scope of the
layer.
Example (Creating a layer from an effectful context)
import { Context, Effect, Layer } from "effect"
class Database extends Context.Service<
Database,
{ readonly query: (sql: string) => Effect.Effect<string> }
>()("Database") {}
const layer = Layer.effectContext(
Effect.succeed(Context.make(Database, {
query: (sql: string) => Effect.succeed(`Query: ${sql}`)
}))
)export const const effectContext: <A, E, R>(
effect: Effect<Context.Context<A>, E, R>
) => Layer<A, E, Exclude<R, Scope.Scope>>
Constructs a layer from an effect that produces all services in a Context.
When to use
Use when you need a Layer that effectfully constructs a Context with
multiple services.
Details
This allows you to create a Layer from an effectful computation that
returns multiple services. The Effect is executed in the scope of the
layer.
Example (Creating a layer from an effectful context)
import { Context, Effect, Layer } from "effect"
class Database extends Context.Service<
Database,
{ readonly query: (sql: string) => Effect.Effect<string> }
>()("Database") {}
const layer = Layer.effectContext(
Effect.succeed(Context.make(Database, {
query: (sql: string) => Effect.succeed(`Query: ${sql}`)
}))
)
effectContext = <function (type parameter) A in <A, E, R>(effect: Effect<Context.Context<A>, E, R>): Layer<A, E, Exclude<R, Scope.Scope>>A, function (type parameter) E in <A, E, R>(effect: Effect<Context.Context<A>, E, R>): Layer<A, E, Exclude<R, Scope.Scope>>E, function (type parameter) R in <A, E, R>(effect: Effect<Context.Context<A>, E, R>): Layer<A, E, Exclude<R, Scope.Scope>>R>(
effect: Effect<Context.Context<A>, E, R>(parameter) effect: {
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 EffectEffect<import ContextContext.type Context.Context = /*unresolved*/ anyContext<function (type parameter) A in <A, E, R>(effect: Effect<Context.Context<A>, E, R>): Layer<A, E, Exclude<R, Scope.Scope>>A>, function (type parameter) E in <A, E, R>(effect: Effect<Context.Context<A>, E, R>): Layer<A, E, Exclude<R, Scope.Scope>>E, function (type parameter) R in <A, E, R>(effect: Effect<Context.Context<A>, E, R>): Layer<A, E, Exclude<R, Scope.Scope>>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>(effect: Effect<Context.Context<A>, E, R>): Layer<A, E, Exclude<R, Scope.Scope>>A, function (type parameter) E in <A, E, R>(effect: Effect<Context.Context<A>, E, R>): Layer<A, E, Exclude<R, Scope.Scope>>E, 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 <A, E, R>(effect: Effect<Context.Context<A>, E, R>): Layer<A, E, Exclude<R, Scope.Scope>>R, import ScopeScope.Scope>> => const fromBuildMemo: <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, with automatic memoization.
Details
This is similar to fromBuild but provides automatic memoization of the layer construction.
The layer will be memoized based on the provided MemoMap.
Example (Memoizing layer construction)
import { Context, Effect, Layer } from "effect"
class Database extends Context.Service<Database, {
readonly query: (sql: string) => Effect.Effect<string>
}>()("Database") {}
const databaseLayer = Layer.fromBuildMemo(() =>
Effect.sync(() =>
Context.make(Database, {
query: (sql: string) => Effect.succeed("result")
})
)
)
fromBuildMemo((_: MemoMap(parameter) _: {
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 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>>
}
effect: Effect<Context.Context<A>, E, R>(parameter) effect: {
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;
}