Effect.Aff

data Aff :: Type -> Type

An Aff a is an asynchronous computation with effects. The computation may either error with an exception, or produce a result of type a. Aff effects are assembled from primitive Effect effects using makeAff or liftEffect.

Instances

• Functor Aff
• Apply Aff
• Applicative Aff
• Bind Aff
• Monad Aff
• (Semigroup a) => Semigroup (Aff a)
• (Monoid a) => Monoid (Aff a)
• Alt Aff
• Plus Aff
• MonadRec Aff

  This instance is provided for compatibility. Aff is always stack-safe within a given fiber. This instance will just result in unnecessary bind overhead.

• MonadThrow Error Aff
• MonadError Error Aff
• MonadEffect Aff
• Lazy (Aff a)
• Parallel ParAff Aff

newtype Fiber a

Represents a forked computation by way of forkAff. Fibers are memoized, so their results are only computed once.

Instances

• Functor Fiber
• Apply Fiber
• Applicative Fiber

data ParAff :: Type -> Type

Applicative for running parallel effects. Any Aff can be coerced to a ParAff and back using the Parallel class.

Instances

• Functor ParAff
• Apply ParAff

  Runs effects in parallel, combining their results.

• Applicative ParAff
• (Semigroup a) => Semigroup (ParAff a)
• (Monoid a) => Monoid (ParAff a)
• Alt ParAff

  Races effects in parallel. Returns the first successful result or the first error if all fail with an exception. Losing branches will be cancelled.

• Plus ParAff
• Alternative ParAff
• Parallel ParAff Aff

newtype Canceler

A cancellation effect for actions run via makeAff. If a Fiber is killed, and an async action is pending, the canceler will be called to clean it up.

Constructors

• Canceler (Error -> Aff Unit)

Instances

• Newtype Canceler _
• Semigroup Canceler
• Monoid Canceler

  A no-op Canceler can be constructed with mempty.

makeAff :: forall a. ((Either Error a -> Effect Unit) -> Effect Canceler) -> Aff a

Constructs an Aff from low-level Effect effects using a callback. A Canceler effect should be returned to cancel the pending action. The supplied callback may be invoked only once. Subsequent invocation are ignored.

launchAff :: forall a. Aff a -> Effect (Fiber a)

Forks an Aff from an Effect context, returning the Fiber.

launchAff_ :: forall a. Aff a -> Effect Unit

Forks an Aff from an Effect context, discarding the Fiber.

launchSuspendedAff :: forall a. Aff a -> Effect (Fiber a)

Suspends an Aff from an Effect context, returning the Fiber.

runAff :: forall a. (Either Error a -> Effect Unit) -> Aff a -> Effect (Fiber Unit)

Forks an Aff from an Effect context and also takes a callback to run when it completes. Returns the pending Fiber.

runAff_ :: forall a. (Either Error a -> Effect Unit) -> Aff a -> Effect Unit

Forks an Aff from an Effect context and also takes a callback to run when it completes, discarding the Fiber.

runSuspendedAff :: forall a. (Either Error a -> Effect Unit) -> Aff a -> Effect (Fiber Unit)

Suspends an Aff from an Effect context and also takes a callback to run when it completes. Returns the suspended Fiber.

forkAff :: forall a. Aff a -> Aff (Fiber a)

Forks an Aff from within a parent Aff context, returning the Fiber.

suspendAff :: forall a. Aff a -> Aff (Fiber a)

Suspends an Aff from within a parent Aff context, returning the Fiber. A suspended Aff is not executed until a consumer observes the result with joinFiber.

supervise :: forall a. Aff a -> Aff a

Creates a new supervision context for some Aff, guaranteeing fiber cleanup when the parent completes. Any pending fibers forked within the context will be killed and have their cancelers run.

attempt :: forall a. Aff a -> Aff (Either Error a)

A monomorphic version of try. Catches thrown errors and lifts them into an Either.

apathize :: forall a. Aff a -> Aff Unit

Ignores any errors.

delay :: Milliseconds -> Aff Unit

Pauses the running fiber.

never :: forall a. Aff a

An async computation which does not resolve.

finally :: forall a. Aff Unit -> Aff a -> Aff a

Runs the first effect after the second, regardless of whether it completed successfully or the fiber was cancelled.

invincible :: forall a. Aff a -> Aff a

Runs an effect such that it cannot be killed.

killFiber :: forall a. Error -> Fiber a -> Aff Unit

Invokes pending cancelers in a fiber and runs cleanup effects. Blocks until the fiber has fully exited.

joinFiber :: Fiber ~> Aff

Blocks until the fiber completes, yielding the result. If the fiber throws an exception, it is rethrown in the current fiber.

cancelWith :: forall a. Aff a -> Canceler -> Aff a

Attaches a custom Canceler to an action. If the computation is canceled, then the custom Canceler will be run afterwards.

bracket :: forall a b. Aff a -> (a -> Aff Unit) -> (a -> Aff b) -> Aff b

Guarantees resource acquisition and cleanup. The first effect may acquire some resource, while the second will dispose of it. The third effect makes use of the resource. Disposal is always run last, regardless. Neither acquisition nor disposal may be cancelled and are guaranteed to run until they complete.

type BracketConditions a b = { completed :: b -> a -> Aff Unit, failed :: Error -> a -> Aff Unit, killed :: Error -> a -> Aff Unit }

generalBracket :: forall a b. Aff a -> BracketConditions a b -> (a -> Aff b) -> Aff b

A general purpose bracket which lets you observe the status of the bracketed action. The bracketed action may have been killed with an exception, thrown an exception, or completed successfully.

nonCanceler :: Canceler

A canceler which does not cancel anything.

effectCanceler :: Effect Unit -> Canceler

A canceler from an Effect action.

fiberCanceler :: forall a. Fiber a -> Canceler

A canceler from a Fiber.

catchError :: forall e m a. MonadError e m => m a -> (e -> m a) -> m a

throwError :: forall e m a. MonadThrow e m => e -> m a

try :: forall e m a. MonadError e m => m a -> m (Either e a)

Return Right if the given action succeeds, Left if it throws.

parallel :: forall f m. Parallel f m => m ~> f

sequential :: forall f m. Parallel f m => f ~> m

newtype Milliseconds

A duration measured in milliseconds.

Constructors

• Milliseconds Number

Instances

• Newtype Milliseconds _
• Eq Milliseconds
• Ord Milliseconds
• Semigroup Milliseconds
• Monoid Milliseconds
• Show Milliseconds
• Duration Milliseconds

data Error :: Type

The type of JavaScript errors

Instances

• Show Error

message :: Error -> String

Get the error message from a JavaScript error

error :: String -> Error

Create a JavaScript error, specifying a message