Halogen.Query

type Tell f = Unit -> f Unit

Type synonym for a "tell-style" query - queries that only cause effects, but that cannot receive a return value.

In a query algebra, a tell constructor carries the algebra's type variable as its last argument. For example:

data Query a
  = SomeTell a
  | SomeOtherTell String a
  | NotATell (Boolean -> a)

Both SomeTell and SomeOtherTell carry a plain a as a value, whereas NotATell has a as the result of a function so is considered to be a "request" (see below).

tell :: forall f. Tell f -> f Unit

Takes a data constructor of query algebra f and creates a tell query.

For example:

data Query a = Tick a

sendTick :: forall o. H.HalogenIO Query o Aff -> Aff (Maybe Unit)
sendTick app = app.query (H.tell Tick)

type Request f a = (a -> a) -> f a

Type synonym for an "request-style" query - queries that can cause effects as well as fetching some information from a component.

In a query algebra, a request constructor carries the algebra's type variable as the return value of a function as its last argument. For example:

data Query a = SomeRequest (Boolean -> a)

request :: forall a f. Request f a -> f a

Takes a data constructor of query algebra f and creates a request query.

For example:

data Query a = GetTickCount (Int -> a)

getTickCount :: forall o. H.HalogenIO Query o Aff -> Aff (Maybe Int)
getTickCount app = app.query (H.request GetTickCount)

getHTMLElementRef :: forall m output slots action surface. RefLabel -> HalogenM surface action slots output m (Maybe HTMLElement)

Retrieves a HTMLElement value that is associated with a Ref in the rendered output of a component. If there is no currently rendered value (or it is not an HTMLElement) for the request will return Nothing.

put :: forall s m. MonadState s m => s -> m Unit

Set the state.

modify_ :: forall m s. MonadState s m => (s -> s) -> m Unit

modify :: forall m s. MonadState s m => (s -> s) -> m s

Modify the state by applying a function to the current state. The returned value is the new state value.

gets :: forall a m s. MonadState s m => (s -> a) -> m a

Get a value which depends on the current state.

get :: forall s m. MonadState s m => m s

Get the current state.

lift :: forall t a m. MonadTrans t => Monad m => m a -> t m a

liftAff :: forall m. MonadAff m => Aff ~> m

liftEffect :: forall m a. MonadEffect m => Effect a -> m a

newtype SubscriptionId

The ID value associated with a subscription. Allows the subscription to be stopped at a later time.

Instances

• Eq SubscriptionId
• Ord SubscriptionId

newtype HalogenM state action slots output m a

The Halogen component eval effect monad.

• state is the component's state
• action is the type of actions; veents internal to the component that can be evaluated
• slots is the set of slots for addressing child components
• output is the type of output messages the component can raise
• m is the monad used during evaluation
• a is the result of the HalogenM expression. Use the following pattern: handleAction :: Action -> H.HalogenM State Action Slots Output m UnithandleQuery :: forall a. Query a -> H.HalogenM State Action Slots Output m (Maybe a)

Constructors

• HalogenM (Free (HalogenF state action slots output m) a)

Instances

• Functor (HalogenM state action slots output m)
• Apply (HalogenM state action slots output m)
• Applicative (HalogenM state action slots output m)
• Bind (HalogenM state action slots output m)
• Monad (HalogenM state action slots output m)
• (Semigroup a) => Semigroup (HalogenM state action slots output m a)
• (Monoid a) => Monoid (HalogenM state action slots output m a)
• (MonadEffect m) => MonadEffect (HalogenM state action slots output m)
• (MonadAff m) => MonadAff (HalogenM state action slots output m)
• Parallel (HalogenAp state action slots output m) (HalogenM state action slots output m)
• MonadTrans (HalogenM state action slots o)
• MonadRec (HalogenM state action slots output m)
• MonadState state (HalogenM state action slots output m)
• (MonadAsk r m) => MonadAsk r (HalogenM state action slots output m)
• (MonadTell w m) => MonadTell w (HalogenM state action slots output m)
• (MonadThrow e m) => MonadThrow e (HalogenM state action slots output m)

data HalogenF state action slots output m a

The Halogen component eval algebra.

• state is the component's state
• action is the type of actions; events internal to the component that can be evaluated
• slots is the set of slots for addressing child components
• output is the type of output messages the component can raise
• m is the monad used during evaluation
• a is the result of the HalogenF expression (see HalogenM for an example).

Constructors

• State (state -> Tuple a state)
• Subscribe (SubscriptionId -> EventSource m action) (SubscriptionId -> a)
• Unsubscribe SubscriptionId a
• Lift (m a)
• ChildQuery (ChildQueryBox slots a)
• Raise output a
• Par (HalogenAp state action slots output m a)
• Fork (HalogenM state action slots output m Unit) (ForkId -> a)
• Kill ForkId a
• GetRef RefLabel (Maybe Element -> a)

Instances

• (Functor m) => Functor (HalogenF state action slots output m)

newtype ForkId

The ID value associated with a forked process. Allows the fork to be killed at a later time.

Instances

• Eq ForkId
• Ord ForkId

unsubscribe :: forall m output slots action state. SubscriptionId -> HalogenM state action slots output m Unit

Unsubscribes a component from an EventSource. If the subscription associated with the ID has already ended this will have no effect.

subscribe' :: forall m output slots action state. (SubscriptionId -> EventSource m action) -> HalogenM state action slots output m Unit

An alternative to subscribe, intended for subscriptions that unsubscribe themselves. Instead of returning the SubscriptionId from subscribe', it is passed into an EventSource constructor. This allows emitted queries to include the SubscriptionId, rather than storing it in the state of the component.

When a component is disposed of any active subscriptions will automatically be stopped and no further subscriptions will be possible during finalization.

subscribe :: forall m output slots action state. EventSource m action -> HalogenM state action slots output m SubscriptionId

Subscribes a component to an EventSource.

When a component is disposed of any active subscriptions will automatically be stopped and no further subscriptions will be possible during finalization.

raise :: forall m output slots action state. output -> HalogenM state action slots output m Unit

Raises an output message for the component.

queryAll :: forall _1 a slot output' query slots label m output action state. Cons label (Slot query output' slot) _1 slots => IsSymbol label => Ord slot => SProxy label -> query a -> HalogenM state action slots output m (Map slot a)

Sends a query to all children of a component at a given slot label.

query :: forall _1 a slot output' query slots label m output action state. Cons label (Slot query output' slot) _1 slots => IsSymbol label => Ord slot => SProxy label -> slot -> query a -> HalogenM state action slots output m (Maybe a)

Sends a query to a child of a component at the specified slot.

kill :: forall m output slots action state. ForkId -> HalogenM state action slots output m Unit

Kills a forked process if it is still running. Attempting to kill a forked process that has already ended will have no effect.

getRef :: forall m output slots action state. RefLabel -> HalogenM state action slots output m (Maybe Element)

Retrieves an Element value that is associated with a Ref in the rendered output of a component. If there is no currently rendered value for the requested ref this will return Nothing.

fork :: forall m output slots action state. HalogenM state action slots output m Unit -> HalogenM state action slots output m ForkId

Starts a HalogenM process running independent from the current eval "thread".

A commonly use case for fork is in component initializers where some async action is started. Normally all interaction with the component will be blocked until the initializer completes, but if the async action is forked instead, the initializer can complete synchronously while the async action continues.

Some care needs to be taken when using a fork that can modify the component state, as it's easy for the forked process to "clobber" the state (overwrite some or all of it with an old value) by mistake.

When a component is disposed of any active forks will automatically be killed. New forks can be started during finalization but there will be no means of killing them.

data HalogenQ query action input a

Constructors

• Initialize a
• Finalize a
• Receive input a
• Action action a
• Query (Coyoneda query a) (Unit -> a)

Instances

• Bifunctor (HalogenQ query action)
• Functor (HalogenQ query action input)

newtype RefLabel

Constructors

• RefLabel String

Instances

• Newtype RefLabel _
• Eq RefLabel
• Ord RefLabel