<I, S>(service: Context.Key<I, S>): (resource: S) => Layer<I>
<I, S>(service: Context.Key<I, S>, resource: Types.NoInfer<S>): Layer<I>Constructs a layer that provides a single service from an already available value.
When to use
Use when you need a Layer that provides a service from an already
constructed implementation without effectful acquisition.
Example (Creating a layer from a service implementation)
import { Context, Effect, Layer } from "effect"
class Database extends Context.Service<Database, {
readonly query: (sql: string) => Effect.Effect<string>
}>()("Database") {}
const DatabaseLive = Layer.succeed(Database, {
query: Effect.fn("Database.query")((sql: string) => Effect.succeed(`Query result: ${sql}`))
})export const const succeed: {
<I, S>(service: Context.Key<I, S>): (
resource: S
) => Layer<I>
<I, S>(
service: Context.Key<I, S>,
resource: Types.NoInfer<S>
): Layer<I>
}
Constructs a layer that provides a single service from an already available
value.
When to use
Use when you need a Layer that provides a service from an already
constructed implementation without effectful acquisition.
Example (Creating a layer from a service implementation)
import { Context, Effect, Layer } from "effect"
class Database extends Context.Service<Database, {
readonly query: (sql: string) => Effect.Effect<string>
}>()("Database") {}
const DatabaseLive = Layer.succeed(Database, {
query: Effect.fn("Database.query")((sql: string) => Effect.succeed(`Query result: ${sql}`))
})
succeed: {
<function (type parameter) I in <I, S>(service: Context.Key<I, S>): (resource: S) => Layer<I>I, function (type parameter) S in <I, S>(service: Context.Key<I, S>): (resource: S) => Layer<I>S>(service: Context.Key<I, S>(parameter) service: {
Identifier: Identifier;
Service: Shape;
key: string;
stack: string | undefined;
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.type Context.Key = /*unresolved*/ anyKey<function (type parameter) I in <I, S>(service: Context.Key<I, S>): (resource: S) => Layer<I>I, function (type parameter) S in <I, S>(service: Context.Key<I, S>): (resource: S) => Layer<I>S>): (resource: Sresource: function (type parameter) S in <I, S>(service: Context.Key<I, S>): (resource: S) => Layer<I>S) => 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) I in <I, S>(service: Context.Key<I, S>): (resource: S) => Layer<I>I>
<function (type parameter) I in <I, S>(service: Context.Key<I, S>, resource: Types.NoInfer<S>): Layer<I>I, function (type parameter) S in <I, S>(service: Context.Key<I, S>, resource: Types.NoInfer<S>): Layer<I>S>(service: Context.Key<I, S>(parameter) service: {
Identifier: Identifier;
Service: Shape;
key: string;
stack: string | undefined;
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.type Context.Key = /*unresolved*/ anyKey<function (type parameter) I in <I, S>(service: Context.Key<I, S>, resource: Types.NoInfer<S>): Layer<I>I, function (type parameter) S in <I, S>(service: Context.Key<I, S>, resource: Types.NoInfer<S>): Layer<I>S>, resource: Types.NoInfer<S>resource: import TypesTypes.type NoInfer<A> = [A][A extends any
? 0
: never]
Prevents TypeScript from inferring a type parameter from a specific
position.
When to use
Use when a function parameter must match an inferred type without becoming
an inference source.
Details
The parameter using NoInfer must still match the inferred type.
Example (Controlling inference)
import type { Types } from "effect"
declare function withDefault<T>(value: T, fallback: Types.NoInfer<T>): T
// T is inferred as "a" | "b" from the first argument only
const result = withDefault<"a" | "b">("a", "b")
NoInfer<function (type parameter) S in <I, S>(service: Context.Key<I, S>, resource: Types.NoInfer<S>): Layer<I>S>): 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) I in <I, S>(service: Context.Key<I, S>, resource: Types.NoInfer<S>): Layer<I>I>
} = function() {
if (function (local var) arguments: IArgumentsarguments.IArguments.length: numberlength === 1) {
return (resource: anyresource: any) => const succeedContext: <A>(
context: Context.Context<A>
) => Layer<A>
Constructs a layer that provides all services in an already available
Context.
When to use
Use when you need a Layer built from an existing Context, including when
you need to provide multiple services at once.
Details
This is a more general version of succeed that allows you to provide
multiple services at once through a Context.
Example (Providing multiple services from a context)
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 context = Context.make(Database, {
query: Effect.fn("Database.query")((sql: string) => Effect.succeed("result"))
}).pipe(
Context.add(Logger, {
log: (msg: string) => Effect.sync(() => console.log(msg))
})
)
const layer = Layer.succeedContext(context)
succeedContext(import ContextContext.make(function (local var) arguments: IArgumentsarguments[0], resource: anyresource))
}
return const succeedContext: <A>(
context: Context.Context<A>
) => Layer<A>
Constructs a layer that provides all services in an already available
Context.
When to use
Use when you need a Layer built from an existing Context, including when
you need to provide multiple services at once.
Details
This is a more general version of succeed that allows you to provide
multiple services at once through a Context.
Example (Providing multiple services from a context)
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 context = Context.make(Database, {
query: Effect.fn("Database.query")((sql: string) => Effect.succeed("result"))
}).pipe(
Context.add(Logger, {
log: (msg: string) => Effect.sync(() => console.log(msg))
})
)
const layer = Layer.succeedContext(context)
succeedContext(import ContextContext.make(function (local var) arguments: IArgumentsarguments[0], function (local var) arguments: IArgumentsarguments[1]))
} as any