<E, A2, A, A3>(options: {
readonly onFailure: (cause: Cause.Cause<E>) => A2
readonly onSuccess: (a: A) => A3
}): <R>(self: Effect<A, E, R>) => Effect<A2 | A3, never, R>
<A, E, R, A2, A3>(
self: Effect<A, E, R>,
options: {
readonly onFailure: (cause: Cause.Cause<E>) => A2
readonly onSuccess: (a: A) => A3
}
): Effect<A2 | A3, never, R>Handles failures by matching the cause of failure.
When to use
Use when you need to fold an Effect while the failure handler inspects the
full Cause.
Details
The matchCause function allows you to handle failures with access to the
full cause of the failure within a fiber.
Example (Matching on success or failure causes)
import { Cause, Effect } from "effect"
const task = Effect.fail("Something went wrong")
const program = Effect.matchCause(task, {
onFailure: (cause) => `Failed: ${Cause.squash(cause)}`,
onSuccess: (value) => `Success: ${value}`
})
Effect.runPromise(program).then(console.log)
// Output: "Failed: Error: Something went wrong"export const const matchCause: {
<E, A2, A, A3>(options: {
readonly onFailure: (
cause: Cause.Cause<E>
) => A2
readonly onSuccess: (a: A) => A3
}): <R>(
self: Effect<A, E, R>
) => Effect<A2 | A3, never, R>
<A, E, R, A2, A3>(
self: Effect<A, E, R>,
options: {
readonly onFailure: (
cause: Cause.Cause<E>
) => A2
readonly onSuccess: (a: A) => A3
}
): Effect<A2 | A3, never, R>
}
Handles failures by matching the cause of failure.
When to use
Use when you need to fold an Effect while the failure handler inspects the
full Cause.
Details
The matchCause function allows you to handle failures with access to the
full cause of the failure within a fiber.
Example (Matching on success or failure causes)
import { Cause, Effect } from "effect"
const task = Effect.fail("Something went wrong")
const program = Effect.matchCause(task, {
onFailure: (cause) => `Failed: ${Cause.squash(cause)}`,
onSuccess: (value) => `Success: ${value}`
})
Effect.runPromise(program).then(console.log)
// Output: "Failed: Error: Something went wrong"
matchCause: {
<function (type parameter) E in <E, A2, A, A3>(options: {
readonly onFailure: (cause: Cause.Cause<E>) => A2;
readonly onSuccess: (a: A) => A3;
}): <R>(self: Effect<A, E, R>) => Effect<A2 | A3, never, R>
function (type parameter) A2 in <E, A2, A, A3>(options: {
readonly onFailure: (cause: Cause.Cause<E>) => A2;
readonly onSuccess: (a: A) => A3;
}): <R>(self: Effect<A, E, R>) => Effect<A2 | A3, never, R>
function (type parameter) A in <E, A2, A, A3>(options: {
readonly onFailure: (cause: Cause.Cause<E>) => A2;
readonly onSuccess: (a: A) => A3;
}): <R>(self: Effect<A, E, R>) => Effect<A2 | A3, never, R>
function (type parameter) A3 in <E, A2, A, A3>(options: {
readonly onFailure: (cause: Cause.Cause<E>) => A2;
readonly onSuccess: (a: A) => A3;
}): <R>(self: Effect<A, E, R>) => Effect<A2 | A3, never, R>
options: {
readonly onFailure: (
cause: Cause.Cause<E>
) => A2
readonly onSuccess: (a: A) => A3
}
onFailure: (cause: Cause.Cause<E>) => A2onFailure: (cause: Cause.Cause<E>(parameter) cause: {
reasons: ReadonlyArray<Reason<E>>;
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 CauseCause.interface Cause<out E>A structured representation of how an Effect failed.
When to use
Use to preserve the full structured failure information for an effect instead
of collapsing it to a single error value.
Details
Access the individual failure entries through the reasons array, then
narrow each entry with
isFailReason
,
isDieReason
, or
- Use
hasFails
/
hasDies
/
hasInterrupts
to test
for the presence of specific reason kinds without iterating.
- Use
findError
/
findDefect
to extract the first value
of a given kind.
- Use
combine
to merge two causes.
Cause implements Equal — two causes with the same reasons (by value)
compare as equal.
Example (Creating and inspecting a cause)
import { Cause } from "effect"
const cause = Cause.fail("Something went wrong")
console.log(cause.reasons.length) // 1
console.log(Cause.isFailReason(cause.reasons[0])) // true
Companion namespace for the Cause interface.
Cause<function (type parameter) E in <E, A2, A, A3>(options: {
readonly onFailure: (cause: Cause.Cause<E>) => A2;
readonly onSuccess: (a: A) => A3;
}): <R>(self: Effect<A, E, R>) => Effect<A2 | A3, never, R>
function (type parameter) A2 in <E, A2, A, A3>(options: {
readonly onFailure: (cause: Cause.Cause<E>) => A2;
readonly onSuccess: (a: A) => A3;
}): <R>(self: Effect<A, E, R>) => Effect<A2 | A3, never, R>
onSuccess: (a: A) => A3onSuccess: (a: Aa: function (type parameter) A in <E, A2, A, A3>(options: {
readonly onFailure: (cause: Cause.Cause<E>) => A2;
readonly onSuccess: (a: A) => A3;
}): <R>(self: Effect<A, E, R>) => Effect<A2 | A3, never, R>
function (type parameter) A3 in <E, A2, A, A3>(options: {
readonly onFailure: (cause: Cause.Cause<E>) => A2;
readonly onSuccess: (a: A) => A3;
}): <R>(self: Effect<A, E, R>) => Effect<A2 | A3, never, R>
function (type parameter) R in <R>(self: Effect<A, E, R>): Effect<A2 | A3, never, R>R>(self: Effect<A, E, R>(parameter) self: {
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 <E, A2, A, A3>(options: {
readonly onFailure: (cause: Cause.Cause<E>) => A2;
readonly onSuccess: (a: A) => A3;
}): <R>(self: Effect<A, E, R>) => Effect<A2 | A3, never, R>
function (type parameter) E in <E, A2, A, A3>(options: {
readonly onFailure: (cause: Cause.Cause<E>) => A2;
readonly onSuccess: (a: A) => A3;
}): <R>(self: Effect<A, E, R>) => Effect<A2 | A3, never, R>
function (type parameter) R in <R>(self: Effect<A, E, R>): Effect<A2 | A3, never, R>R>) => 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) A2 in <E, A2, A, A3>(options: {
readonly onFailure: (cause: Cause.Cause<E>) => A2;
readonly onSuccess: (a: A) => A3;
}): <R>(self: Effect<A, E, R>) => Effect<A2 | A3, never, R>
function (type parameter) A3 in <E, A2, A, A3>(options: {
readonly onFailure: (cause: Cause.Cause<E>) => A2;
readonly onSuccess: (a: A) => A3;
}): <R>(self: Effect<A, E, R>) => Effect<A2 | A3, never, R>
function (type parameter) R in <R>(self: Effect<A, E, R>): Effect<A2 | A3, never, R>R>
<function (type parameter) A in <A, E, R, A2, A3>(self: Effect<A, E, R>, options: {
readonly onFailure: (cause: Cause.Cause<E>) => A2;
readonly onSuccess: (a: A) => A3;
}): Effect<A2 | A3, never, R>
function (type parameter) E in <A, E, R, A2, A3>(self: Effect<A, E, R>, options: {
readonly onFailure: (cause: Cause.Cause<E>) => A2;
readonly onSuccess: (a: A) => A3;
}): Effect<A2 | A3, never, R>
function (type parameter) R in <A, E, R, A2, A3>(self: Effect<A, E, R>, options: {
readonly onFailure: (cause: Cause.Cause<E>) => A2;
readonly onSuccess: (a: A) => A3;
}): Effect<A2 | A3, never, R>
function (type parameter) A2 in <A, E, R, A2, A3>(self: Effect<A, E, R>, options: {
readonly onFailure: (cause: Cause.Cause<E>) => A2;
readonly onSuccess: (a: A) => A3;
}): Effect<A2 | A3, never, R>
function (type parameter) A3 in <A, E, R, A2, A3>(self: Effect<A, E, R>, options: {
readonly onFailure: (cause: Cause.Cause<E>) => A2;
readonly onSuccess: (a: A) => A3;
}): Effect<A2 | A3, never, R>
self: Effect<A, E, R>(parameter) self: {
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, R, A2, A3>(self: Effect<A, E, R>, options: {
readonly onFailure: (cause: Cause.Cause<E>) => A2;
readonly onSuccess: (a: A) => A3;
}): Effect<A2 | A3, never, R>
function (type parameter) E in <A, E, R, A2, A3>(self: Effect<A, E, R>, options: {
readonly onFailure: (cause: Cause.Cause<E>) => A2;
readonly onSuccess: (a: A) => A3;
}): Effect<A2 | A3, never, R>
function (type parameter) R in <A, E, R, A2, A3>(self: Effect<A, E, R>, options: {
readonly onFailure: (cause: Cause.Cause<E>) => A2;
readonly onSuccess: (a: A) => A3;
}): Effect<A2 | A3, never, R>
options: {
readonly onFailure: (
cause: Cause.Cause<E>
) => A2
readonly onSuccess: (a: A) => A3
}
onFailure: (cause: Cause.Cause<E>) => A2onFailure: (cause: Cause.Cause<E>(parameter) cause: {
reasons: ReadonlyArray<Reason<E>>;
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 CauseCause.interface Cause<out E>A structured representation of how an Effect failed.
When to use
Use to preserve the full structured failure information for an effect instead
of collapsing it to a single error value.
Details
Access the individual failure entries through the reasons array, then
narrow each entry with
isFailReason
,
isDieReason
, or
- Use
hasFails
/
hasDies
/
hasInterrupts
to test
for the presence of specific reason kinds without iterating.
- Use
findError
/
findDefect
to extract the first value
of a given kind.
- Use
combine
to merge two causes.
Cause implements Equal — two causes with the same reasons (by value)
compare as equal.
Example (Creating and inspecting a cause)
import { Cause } from "effect"
const cause = Cause.fail("Something went wrong")
console.log(cause.reasons.length) // 1
console.log(Cause.isFailReason(cause.reasons[0])) // true
Companion namespace for the Cause interface.
Cause<function (type parameter) E in <A, E, R, A2, A3>(self: Effect<A, E, R>, options: {
readonly onFailure: (cause: Cause.Cause<E>) => A2;
readonly onSuccess: (a: A) => A3;
}): Effect<A2 | A3, never, R>
function (type parameter) A2 in <A, E, R, A2, A3>(self: Effect<A, E, R>, options: {
readonly onFailure: (cause: Cause.Cause<E>) => A2;
readonly onSuccess: (a: A) => A3;
}): Effect<A2 | A3, never, R>
onSuccess: (a: A) => A3onSuccess: (a: Aa: function (type parameter) A in <A, E, R, A2, A3>(self: Effect<A, E, R>, options: {
readonly onFailure: (cause: Cause.Cause<E>) => A2;
readonly onSuccess: (a: A) => A3;
}): Effect<A2 | A3, never, R>
function (type parameter) A3 in <A, E, R, A2, A3>(self: Effect<A, E, R>, options: {
readonly onFailure: (cause: Cause.Cause<E>) => A2;
readonly onSuccess: (a: A) => A3;
}): Effect<A2 | A3, never, R>
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) A2 in <A, E, R, A2, A3>(self: Effect<A, E, R>, options: {
readonly onFailure: (cause: Cause.Cause<E>) => A2;
readonly onSuccess: (a: A) => A3;
}): Effect<A2 | A3, never, R>
function (type parameter) A3 in <A, E, R, A2, A3>(self: Effect<A, E, R>, options: {
readonly onFailure: (cause: Cause.Cause<E>) => A2;
readonly onSuccess: (a: A) => A3;
}): Effect<A2 | A3, never, R>
function (type parameter) R in <A, E, R, A2, A3>(self: Effect<A, E, R>, options: {
readonly onFailure: (cause: Cause.Cause<E>) => A2;
readonly onSuccess: (a: A) => A3;
}): Effect<A2 | A3, never, R>
import internalinternal.const matchCause: {
<E, A2, A, A3>(options: {
readonly onFailure: (
cause: Cause.Cause<E>
) => A2
readonly onSuccess: (a: A) => A3
}): <R>(
self: Effect.Effect<A, E, R>
) => Effect.Effect<A2 | A3, never, R>
<A, E, R, A2, A3>(
self: Effect.Effect<A, E, R>,
options: {
readonly onFailure: (
cause: Cause.Cause<E>
) => A2
readonly onSuccess: (a: A) => A3
}
): Effect.Effect<A2 | A3, never, R>
}