observable-slice

observable-slice

A slice of state that can be observed with react hooks, or callbacks.
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About

Create an observable for global state that can be subscribed to with react hooks, or callbacks.

Getting Started

To get a local copy up and running follow these simple steps, or see the Code Sandbox

npm i observable-slice

Create a slice of state

import { create } from 'observable-slice';

const countSlice = create({
  initState: 0,
  pubs: {
    increment: (prev, by: number) => prev + by,
  },
  useSubs: {
    useCount: () => ({
      select: s => s,
    }),
    useCount5: () => ({
      select: s => s,
      isEqual: (prev, next) => next % 5 !== 0,
    }),
  },
});

const CountSub = () => {
  const count = countSlice.useCount();
  return <span>{count}</span>;
};

const CountPub = () => {
  return <button onClick={() => countSlice.increment(1)}>count + 1</button>;
};

const CountSub5 = () => {
  const count5 = countSlice.useCount5();
  return <span>{count5}</span>;
};

export const CountApp = () => {
  return (
    <>
      <CountSub />
      <CountPub />
      <CountSub5 />
    </>
  );
};

Props

create

A function that creates a slice of state with the following props:

name	type	default	description
initState	JSON		The uncontrolled initial state of the slice.
pubs	{} | undefined		The publishers will replace the slice then notify the subscribers. It is recommended to wrap these reducers with immer's produce: https://immerjs.github.io/immer/update-patterns. If a publisher needs more than one parameter, it may be passed as an object.
useSubs	{} | undefined		The subscribers will be available as react hooks and must be used inside of a react functional component. By default, all selectors will be memoized. If you would like to use a selector that is not memoized, try slice.useSub.
notifyMiddleware	(notify: () => void) => () => void		You may add a debounce function here.

slice

The observable returned from a create function

name	type	default	description
pub	fn		Used to publish updates to subscribers by mutating the slice. This is an alternative way to replace state. You may use slice.pub instead defining reducers inside of create.pubs. It iss also recommended to wrap pubs in immer's produce. All publishers may be used outside of the react.
sub	fn		Used to subscribe to updates from publishers. This is an alternative way to subscribe to state that can be used outside of a react.
useSub	fn		A react hook that will cause re renders to its component when the selected portion of the slice (param0) changes based on the isEqual fn (param1).
$pub	fn		Each entry defined in create.pubs will be available on the returned slice. If you would like to pass more than one arg to the reducer, you may put them into an object
$useSub	fn		Each entry defined in create.subs will create a react hook that may be consumed to subscribe to the slice. These hooks may also accept one parameter. For example, the useTodo subscription may accept the id of the todo to subscribe to.
logger	fn		Add additionally functionality to the slice before it handles each eventFor example a logger, or a persister.

Roadmap

See the open issues for a list of proposed features (and known issues).

License

See LICENSE for more information.

Contact

Teague Stockwell - LinkedIn