Halogen.Query

type Action f = Unit -> f Unit

Type synonym for an "action" - An action only causes effects and has no result value.

In a query algebra, an action is any constructor that carries the algebra's type variable as a value. For example:

data Query a
  = SomeAction a
  | SomeOtherAction String a
  | NotAnAction (Boolean -> a)

Both SomeAction and SomeOtherAction have a as a value so they are considered actions, whereas NotAnAction has a as the result of a function so is considered to be a "request" (see below).

action :: forall f. Action f -> f Unit

Takes a data constructor of query algebra f and creates an action.

For example:

data Query a = Tick a

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

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

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

In a query algebra, an action is any constructor that carries the algebra's type variable as the return value of a function. For example:

data Query a = SomeRequest (Boolean -> a)

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

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

For example:

data Query a = GetTickCount (Int -> a)

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

query :: forall s f g p o m a. Eq p => p -> g a -> HalogenM s f g p o m (Maybe a)

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

query' :: forall s f g g' m p p' o a. Eq p' => ChildPath g g' p p' -> p -> g a -> HalogenM s f g' p' o m (Maybe a)

Sends a query to a child of a component at the specified slot, using a ChildPath to discriminate the type of child component to query.

queryAll :: forall s f g p o m a. Ord p => g a -> HalogenM s f g p o m (Map p a)

Sends a query to all children of a component.

queryAll' :: forall s f g g' p p' o m a. Ord p => Eq p' => ChildPath g g' p p' -> g a -> HalogenM s f g' p' o m (Map p a)

Sends a query to all children of a specific type within a component, using a ChildPath to discriminate the type of child component to query.

getHTMLElementRef :: forall s f g p o m. RefLabel -> HalogenM s f g p o m (Maybe HTMLElement)

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

Set the state.

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

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

Get a value which depends on the current state.

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

Get the current state.

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

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

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

data SubscribeStatus

The status of an EventSource subscription. When a query raised by an EventSource evaluates to Done the producer will be unsubscribed from.

Constructors

• Listening
• Done

Instances

• Eq SubscribeStatus
• Ord SubscribeStatus

newtype EventSource f m

eventSource_ :: forall f m. MonadAff m => (Effect Unit -> Effect Unit) -> f SubscribeStatus -> EventSource f m

Creates an EventSource for a callback that accepts no arguments.

• The first argument is the function that attaches the listener.
• The second argument is the query to raise whenever the listener is triggered.

eventSource :: forall f m a. MonadAff m => ((a -> Effect Unit) -> Effect Unit) -> (a -> Maybe (f SubscribeStatus)) -> EventSource f m

Creates an EventSource for a callback that accepts one argument.

• The first argument is the function that attaches the listener.
• The second argument is a handler that optionally produces a value in f.

newtype HalogenM s (f :: Type -> Type) g p o m a

Constructors

• HalogenM (Free (HalogenF s f g p o m) a)

Instances

• Functor (HalogenM s f g p o m)
• Apply (HalogenM s f g p o m)
• Applicative (HalogenM s f g p o m)
• Bind (HalogenM s f g p o m)
• Monad (HalogenM s f g p o m)
• (MonadEffect m) => MonadEffect (HalogenM s f g p o m)
• (MonadAff m) => MonadAff (HalogenM s f g p o m)
• Parallel (HalogenAp s f g p o m) (HalogenM s f g p o m)
• MonadTrans (HalogenM s f g p o)
• MonadRec (HalogenM s f g p o m)
• MonadState s (HalogenM s f g p o m)
• (MonadAsk r m) => MonadAsk r (HalogenM s f g p o m)
• (MonadTell w m) => MonadTell w (HalogenM s f g p o m)

data HalogenF s (f :: Type -> Type) g p o m a

The Halogen component algebra

Constructors

• State (s -> Tuple a s)
• Subscribe (EventSource f m) a
• Lift (m a)
• Halt String
• GetSlots (List p -> a)
• CheckSlot p (Boolean -> a)
• ChildQuery p (Coyoneda g a)
• Raise o a
• Par (HalogenAp s f g p o m a)
• Fork (Fork (HalogenM s f g p o m) a)
• GetRef RefLabel (Maybe Element -> a)

Instances

• (Functor m) => Functor (HalogenF s f g p o m)

subscribe :: forall s f g p o m. EventSource f m -> HalogenM s f g p o m Unit

Provides a way of having a component subscribe to an EventSource from within an Eval function.

raise :: forall s f g p o m. o -> HalogenM s f g p o m Unit

Raises an output message for the component.

mkQuery :: forall s f g p o m a. Eq p => p -> g a -> HalogenM s f g p o m a

getSlots :: forall s f g p o m. HalogenM s f g p o m (List p)

getRef :: forall s f g p o m. RefLabel -> HalogenM s f g p o m (Maybe Element)

fork :: forall s f g p o m a. MonadAff m => HalogenM s f g p o m a -> HalogenM s f g p o m (Error -> m Unit)

checkSlot :: forall s f g p o m. p -> HalogenM s f g p o m Boolean

newtype RefLabel

Constructors

• RefLabel String

Instances

• Newtype RefLabel _
• Eq RefLabel
• Ord RefLabel