Halo is a Halogen-inspired interface and runtime for your components, designed to integrate with React.
It is implemented as a hook: useHalo
; and simple component helpers are included: component
and component_
.
Module documentation is published on Pursuit.
Using with Spago
Update the additions in your packages.dhall
:
let additions =
{ react-halo =
{ dependencies = [ "aff", "free", "freeap", "react-basic-hooks", "wire" ]
, repo = "https://github.com/robertdp/purescript-react-halo.git"
, version = "v0.2.3"
}
, wire =
{ dependencies = [ "aff", "filterable", "refs", "unsafe-reference" ]
, repo = "https://github.com/robertdp/purescript-wire.git"
, version = "v0.5.0"
}
}
Then install with Spago:
$ spago install react-halo
Whether you are using the hook or one of the component helpers, the main feature that Halo provides is the eval
function. It looks like:
Lifecycle props action -> HaloM props state action m a
where Lifecycle
is:
data Lifecycle props action
= Initialize props -- when the component mounts
| Update props props -- when the props change
| Action action -- when an action is dispatched
| Finalize -- when the component unmounts
HaloM
is also a monad transformer, and so you can lift any monad m
logic into HaloM
. Just be aware that in order to run the logic, Halo requires that you hoist
(convert) your chosen monad into Aff
before returning it.
hoist :: forall props state action m m'. Functor m => (m ~> m') -> HaloM props state action m ~> HaloM props state action m'
Example:
invertReaderT x = ReaderT \env -> Halo.hoist (flip runReaderT env) x
props :: forall props action state m. HaloM props state action m props
Example:
fireOnChange value = do
{ onChange } <- Halo.props
onChange value
HaloM
doesn't have any special interface for reading and modifying state, instead providing an instance of MonadState for flexibility.
Subscriptions registered using these functions are automatically tracked by Halo.
subscribe :: forall props state action m. Event action -> HaloM props state action m SubscriptionId
unsubscribe :: forall m action state props. SubscriptionId -> HaloM props state action m Unit
Event
comes from the Wire library.
There is also a version for subscriptions that want to unsubscribe themselves:
subscribe' :: forall m action state props. (SubscriptionId -> Event action) -> HaloM props state action m SubscriptionId
Any subscriptions that remain when the component is unmounted are automatically unsubscribed. This prevents requiring manual clean up in the Finalize
lifecycle event. Also note that new subscriptions will not be created once the Finalize
event has been fired.
Also provided are functions for creating and killing forks which launch processes in separate "threads" (or as useful an approximation as we can get in JavaScript):
fork :: forall m action state props. HaloM props state action m Unit -> HaloM props state action m ForkId
kill :: forall m action state props. ForkId -> HaloM props state action m Unit
Similarly to subscriptions, when the component unmounts all still-running forks will be killed. However new forks can be created during the Finalize
phase but there is no way of killing them (as with Halogen).
Finally HaloM
provides an instance of Parallel
for converting back and forth between HaloAp
, it's applicative counterpart. This allows any logic to be easily converted to run in parallel
or sequential
ly.