<A, E = never>(): Effect.Effect<TxDeferred<A, E>>Creates a new empty TxDeferred.
When to use
Use to create a transactional deferred that can be completed exactly once.
Example (Creating a transactional deferred)
import { Effect, Option, TxDeferred } from "effect"
const program = Effect.gen(function*() {
const deferred = yield* TxDeferred.make<string, Error>()
const state = yield* TxDeferred.poll(deferred)
console.log(Option.isNone(state)) // true
})export const const make: <
A,
E = never
>() => Effect.Effect<TxDeferred<A, E>>
Creates a new empty TxDeferred.
When to use
Use to create a transactional deferred that can be completed exactly once.
Example (Creating a transactional deferred)
import { Effect, Option, TxDeferred } from "effect"
const program = Effect.gen(function*() {
const deferred = yield* TxDeferred.make<string, Error>()
const state = yield* TxDeferred.poll(deferred)
console.log(Option.isNone(state)) // true
})
make = <function (type parameter) A in <A, E = never>(): Effect.Effect<TxDeferred<A, E>>A, function (type parameter) E in <A, E = never>(): Effect.Effect<TxDeferred<A, E>>E = never>(): import EffectEffect.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<interface TxDeferred<in out A, in out E = never>A transactional deferred is a write-once cell readable within transactions.
Readers block (retry the transaction) until a value is committed, and writers
succeed only on the first call; subsequent writes return false.
When to use
Use to coordinate transaction-local readers and one-time completion with a
success or failure result.
Example (Completing a transactional deferred)
import { Effect, TxDeferred } from "effect"
const program = Effect.gen(function*() {
const deferred = yield* TxDeferred.make<number>()
// Complete the deferred
const first = yield* TxDeferred.succeed(deferred, 42)
console.log(first) // true
// Second write is a no-op
const second = yield* TxDeferred.succeed(deferred, 99)
console.log(second) // false
// Read the value
const value = yield* TxDeferred.await(deferred)
console.log(value) // 42
})
TxDeferred<function (type parameter) A in <A, E = never>(): Effect.Effect<TxDeferred<A, E>>A, function (type parameter) E in <A, E = never>(): Effect.Effect<TxDeferred<A, E>>E>> =>
import EffectEffect.const map: {
<A, B>(f: (a: A) => B): <E, R>(
self: Effect<A, E, R>
) => Effect<B, E, R>
<A, E, R, B>(
self: Effect<A, E, R>,
f: (a: A) => B
): Effect<B, E, R>
}
import TxRefTxRef.const make: <Option<Result<A, E>>>(initial: Option<Result<A, E>>) => Effect.Effect<TxRef.TxRef<Option<Result<A, E>>>, never, never>Creates a new TxRef with the specified initial value.
When to use
Use to create a TxRef inside an Effect workflow.
Example (Creating transactional references)
import { Effect, TxRef } from "effect"
const program = Effect.gen(function*() {
// Create a transactional reference with initial value
const counter = yield* TxRef.make(0)
const name = yield* TxRef.make("Alice")
// Use in transactions
yield* Effect.tx(Effect.gen(function*() {
yield* TxRef.set(counter, 42)
yield* TxRef.set(name, "Bob")
}))
console.log(yield* TxRef.get(counter)) // 42
console.log(yield* TxRef.get(name)) // "Bob"
})
make<type Option<A> = O.None<A> | O.Some<A>The Option data type represents optional values. An Option<A> is either
Some<A>, containing a value of type A, or None, representing absence.
When to use
Use to represent initial values that may not yet exist
- Returning from partial functions (not defined for all inputs)
- Managing optional fields in data structures
Namespace containing utility types for Option.
When to use
Use to access type-level helpers associated with Option.
Option<type Result<A, E = never> = Res.Success<A, E> | Res.Failure<A, E>A value that is either Success<A, E> or Failure<A, E>.
When to use
Use when both success and failure should remain available as data and
Option would lose failure information.
Details
- Use
succeed
/
fail
to construct
- Use
match
to fold both branches
- Use
isSuccess
/
isFailure
to narrow the type
E defaults to never, so Result<number> means a result that cannot fail.
Example (Creating and matching a Result)
import { Result } from "effect"
const success = Result.succeed(42)
const failure = Result.fail("something went wrong")
const message = Result.match(success, {
onSuccess: (value) => `Success: ${value}`,
onFailure: (error) => `Error: ${error}`
})
console.log(message)
// Output: "Success: 42"
Namespace containing type-level utilities for extracting the inner types
of a Result.
Example (Extracting inner types)
import type { Result } from "effect"
type R = Result.Result<number, string>
// number
type A = Result.Result.Success<R>
// string
type E = Result.Result.Failure<R>
Result<function (type parameter) A in <A, E = never>(): Effect.Effect<TxDeferred<A, E>>A, function (type parameter) E in <A, E = never>(): Effect.Effect<TxDeferred<A, E>>E>>>(import OO.const none: <A = never>() => Option<A>Creates an Option representing the absence of a value.
When to use
Use to represent a missing or uninitialized value, such as returning "no
result" from a function.
Details
- Returns
Option<never>, which is a subtype of Option<A> for any A
- Always returns the same singleton instance
Example (Creating an empty Option)
import { Option } from "effect"
// ┌─── Option<never>
// ▼
const noValue = Option.none()
console.log(noValue)
// Output: { _id: 'Option', _tag: 'None' }
none()), const makeTxDeferred: <A, E>(
ref: TxRef.TxRef<Option<Result<A, E>>>
) => TxDeferred<A, E>