Restorative is a simple ReScript state management library. Comes with React hooks.
While you can get very far with core ReScript and React functionality, you may find yourself with global state to manage. Restorative
may be your solution. Features a reducer store with performant subscriptions and selectors.
Similar projects in JavaScript include Redux and zustand.
npm install --save @dck/restorative
# or
yarn add @dck/restorative
Add to rescript.json
"bs-dependencies": [
"restorative"
]
type state = int
type action =
| Increment
| Decrement
let api =
Restorative.createStore(0, (state, action) =>
switch (action) {
| Increment => state + 1
| Decrement => state - 1
}
)
let {dispatch, subscribe, getState} = api
let unsubscribe = subscribe(state => Js.log(state))
dispatch(Increment) // calls subscriptions
getState() // 1
unsubscribe()
let {useStore, dispatch} = api
@react.component
let make = () => {
let state = useStore()
<button onClick={_ => dispatch(Increment)}>
{React.string(string_of_int(state))}
</button>
}
type state = {
a: int,
b: int,
}
type action =
| IncrementA
| IncrementB
let {subscribeWithSelector, dispatch} =
createStore({a: 0, b: 0}, (state, action) =>
switch (action) {
| IncrementA => {...state, a: state.a + 1}
| IncrementB => {...state, b: state.b + 1}
}
)
subscribeWithSelector(state => state.a, a => Js.log(a))
dispatch(IncrementA) // calls listener
dispatch(IncrementB) // does not call listener
@react.component
let make = () => {
let a = useStoreWithSelector(state => state.a)
// Only updates when a changes
...
}
Restorative
will not call listeners if the selected state has not "changed" (entire state if no selector). By default, uses Object.is
for equality checking. All subscribe
and useStore
functions take an optional ~areEqual: ('state, 'state) => bool
.
useStoreWithSelector(
state => [state.a, state.b],
~areEqual=(a, b) => a == b
)
We get all the benefits of rescript's great type system. Instead of plain JavaScript objects, we use variants to model actions. All operations have sound types and some work is moved to compile time (e.g. action creators).
Restorative
maintains a list of subscriptions for each store. In contrast, React Context iterates through all children Fiber nodes to find context consumers when the context value changes. React context is not well suited for fast-changing data. Subscriptions, on the other hand, allow for more precise operations at the cost of more complexity (maintaining list of subscribers).
Redux applications typically use a single global store and dispatcher. With Restorative
, you can create multiple stores, each with its own dispatcher. This allows better separation of state logic.