Application entry point

Optional Logging for debugging miso internals (useful to see if prerendering is successful)

An effect represents the results of an update action.

It consists of the updated model and a list of subscriptions. Each Sub is run in a new thread so there is no risk of accidentally blocking the application.

Type synonym for constructing event subscriptions.

The Sink callback is used to dispatch actions which are then fed back to the update function.

A monad for succinctly expressing model transitions in the update function.

Transition is a state monad so it abstracts over manually passing the model around. It's also a writer monad where the accumulator is a list of scheduled IO actions. Multiple actions can be scheduled using Control.Monad.Writer.Class.tell from the mtl library and a single action can be scheduled using scheduleIO.

Tip: use the Transition monad in combination with the stateful lens operators (all operators ending in "="). The following example assumes the lenses field1, counter and field2 are in scope and that the LambdaCase language extension is enabled:

myApp = App
  { update = fromTransition . \case
      MyAction1 -> do
        field1 .= value1
        counter += 1
      MyAction2 -> do
        field2 %= f
        scheduleIO $ do
          putStrLn "Hello"
          putStrLn "World!"
  , ...
  }

Turn a transition that schedules subscriptions that consume actions of type a into a transition that schedules subscriptions that consume actions of type b using the supplied function of type a -> b.

Convert a Transition computation to a function that can be given to update.

Convert an update function to a Transition computation.

Schedule a single IO action for later execution.

Note that multiple IO action can be scheduled using Control.Monad.Writer.Class.tell from the mtl library.

Like scheduleIO but doesn't cause an action to be dispatched to the update function.

This is handy for scheduling IO computations where you don't care about their results or when they complete.

Like scheduleIO_ but generalized to any instance of Foldable

This is handy for scheduling IO computations that return a Maybe value

Like scheduleIO but schedules a subscription which is an IO computation that has access to a Sink which can be used to asynchronously dispatch actions to the update function.

A use-case is scheduling an IO computation which creates a 3rd-party JS widget which has an associated callback. The callback can then call the sink to turn events into actions. To do this without accessing a sink requires going via a Subscription which introduces a leaky-abstraction.