<I, S>(service: Context.Key<I, S>): Effect<S, never, I>Accesses a service from the context.
Example (Accessing a required service)
import { Context, Effect } from "effect"
interface Database {
readonly query: (sql: string) => Effect.Effect<string>
}
const Database = Context.Service<Database>("Database")
const program = Effect.gen(function*() {
const db = yield* Effect.service(Database)
return yield* db.query("SELECT * FROM users")
})export const const service: <I, S>(
service: Context.Key<I, S>
) => Effect<S, never, I>
Accesses a service from the context.
Example (Accessing a required service)
import { Context, Effect } from "effect"
interface Database {
readonly query: (sql: string) => Effect.Effect<string>
}
const Database = Context.Service<Database>("Database")
const program = Effect.gen(function*() {
const db = yield* Effect.service(Database)
return yield* db.query("SELECT * FROM users")
})
service: <function (type parameter) I in <I, S>(service: Context.Key<I, S>): Effect<S, never, I>I, function (type parameter) S in <I, S>(service: Context.Key<I, S>): Effect<S, never, 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>): Effect<S, never, I>I, function (type parameter) S in <I, S>(service: Context.Key<I, S>): Effect<S, never, I>S>) => 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) S in <I, S>(service: Context.Key<I, S>): Effect<S, never, I>S, never, function (type parameter) I in <I, S>(service: Context.Key<I, S>): Effect<S, never, I>I> = import internalinternal.const service: <I, S>(
service: Context.Key<I, S>
) => Effect.Effect<S, never, I>