<R>(context: Context.Context<R>): <A, E>(
effect: Effect<A, E, R>
) => Exit.Exit<A, E>Runs an effect synchronously with provided services, returning an Exit result safely.
When to use
Use when you already have a Context and need a synchronous Exit instead of
throwing on failure.
Example (Running synchronously with services as Exit)
import { Context, Effect, Exit } from "effect"
// Define a logger service
const Logger = Context.Service<{
log: (msg: string) => void
}>("Logger")
const program = Effect.gen(function*() {
const logger = yield* Effect.service(Logger)
logger.log("Computing result...")
return 42
})
// Prepare context
const context = Context.make(Logger, {
log: (msg) => console.log(`[LOG] ${msg}`)
})
const exit = Effect.runSyncExitWith(context)(program)
if (Exit.isSuccess(exit)) {
console.log(`Success: ${exit.value}`)
} else {
console.log(`Failure: ${exit.cause}`)
}
// Output:
// [LOG] Computing result...
// Success: 42export const const runSyncExitWith: <R>(
context: Context.Context<R>
) => <A, E>(
effect: Effect<A, E, R>
) => Exit.Exit<A, E>
Runs an effect synchronously with provided services, returning an Exit result safely.
When to use
Use when you already have a Context and need a synchronous Exit instead of
throwing on failure.
Example (Running synchronously with services as Exit)
import { Context, Effect, Exit } from "effect"
// Define a logger service
const Logger = Context.Service<{
log: (msg: string) => void
}>("Logger")
const program = Effect.gen(function*() {
const logger = yield* Effect.service(Logger)
logger.log("Computing result...")
return 42
})
// Prepare context
const context = Context.make(Logger, {
log: (msg) => console.log(`[LOG] ${msg}`)
})
const exit = Effect.runSyncExitWith(context)(program)
if (Exit.isSuccess(exit)) {
console.log(`Success: ${exit.value}`)
} else {
console.log(`Failure: ${exit.cause}`)
}
// Output:
// [LOG] Computing result...
// Success: 42
runSyncExitWith: <function (type parameter) R in <R>(context: Context.Context<R>): <A, E>(effect: Effect<A, E, R>) => Exit.Exit<A, E>R>(
context: Context.Context<R>(parameter) context: {
mapUnsafe: ReadonlyMap<string, any>;
mutable: boolean;
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.interface Context<in Services>Immutable collection of service implementations used for dependency
injection in Effect programs.
Details
The type parameter tracks the service identifiers available in the context.
At runtime, services are stored by each key's string key.
Example (Creating a context with multiple services)
import { Context } from "effect"
// Create a context with multiple services
const Logger = Context.Service<{ log: (msg: string) => void }>("Logger")
const Database = Context.Service<{ query: (sql: string) => string }>(
"Database"
)
const context = Context.make(Logger, {
log: (msg: string) => console.log(msg)
})
.pipe(Context.add(Database, { query: (sql) => `Result: ${sql}` }))
Context<function (type parameter) R in <R>(context: Context.Context<R>): <A, E>(effect: Effect<A, E, R>) => Exit.Exit<A, E>R>
) => <function (type parameter) A in <A, E>(effect: Effect<A, E, R>): Exit.Exit<A, E>A, function (type parameter) E in <A, E>(effect: Effect<A, E, R>): Exit.Exit<A, E>E>(effect: Effect<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;
}
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) A in <A, E>(effect: Effect<A, E, R>): Exit.Exit<A, E>A, function (type parameter) E in <A, E>(effect: Effect<A, E, R>): Exit.Exit<A, E>E, function (type parameter) R in <R>(context: Context.Context<R>): <A, E>(effect: Effect<A, E, R>) => Exit.Exit<A, E>R>) => import ExitExit.type Exit<A, E = never> = Exit.Success<A, E> | Exit.Failure<A, E>Represents the result of an Effect computation.
When to use
Use when you need to synchronously inspect whether an Effect computation
succeeded or failed.
Details
An Exit<A, E> is either Success<A, E> containing a value of type A, or
Failure<A, E> containing a Cause<E> describing why the computation
failed.
Since Exit is also an Effect, you can yield it inside Effect.gen.
Example (Pattern matching on an Exit)
import { Exit } from "effect"
const success: Exit.Exit<number> = Exit.succeed(42)
const failure: Exit.Exit<number, string> = Exit.fail("error")
const result = Exit.match(success, {
onSuccess: (value) => `Got value: ${value}`,
onFailure: (cause) => `Got error: ${cause}`
})
Namespace containing helper types shared by Exit values.
When to use
Use to reference helper types that describe the shared structure of Exit
values.
Exit<function (type parameter) A in <A, E>(effect: Effect<A, E, R>): Exit.Exit<A, E>A, function (type parameter) E in <A, E>(effect: Effect<A, E, R>): Exit.Exit<A, E>E> = import internalinternal.const runSyncExitWith: <R>(
context: Context.Context<R>
) => <A, E>(
effect: Effect.Effect<A, E, R>
) => Exit.Exit<A, E>