Sub.md

Module Elm.Platform.Sub

Re-exported from Elm.Monoid:

none

none :: forall m. Monoid m => m

Produce an "empty" value of the relevant type.

Equivalent to Purescript's mempty.

batch

batch :: forall f m. Foldable f => Monoid m => f m -> m

Smush together a bunch of things.

Equivalent to Purescript's fold

Re-exported from Elm.Platform:

Sub

newtype Sub msg

A subscription is a way of telling Elm, “Hey, let me know if anything interesting happens over there!” So if you want to listen for messages on a web socket, you would tell Elm to create a subscription. If you want to get clock ticks, you would tell Elm to subscribe to that. The cool thing here is that this means Elm manages all the details of subscriptions instead of you. So if a web socket goes down, you do not need to manually reconnect with an exponential backoff strategy, Elm does this all for you behind the scenes!

Every Sub specifies (1) which effects you need access to and (2) the type of messages that will come back into your application.

Note: Do not worry if this seems confusing at first! As with every Elm user ever, subscriptions will make more sense as you work through the Elm Architecture Tutorial and see how they fit into a real application!

Instances

Functor Sub
Semigroup (Sub msg)
Monoid (Sub msg)

Re-exported from Prelude:

map

map :: forall a b f. Functor f => (a -> b) -> f a -> f b