Undo functionality for the recoil state management library

This is an incredibly early library and much like recoil itself the api will almost certainly change. Right now the functionality is very basic, but expect it to come much more robust over time and those changes might not be backwards compatible at the moment.

recoil-undo relies on both React and Recoil installed as peer dependencies so make sure they are installed as well.

npm install --save recoil-undo

or

yarn add recoil-undo

Make sure that you include you put RecoilUndoRoot under RecoilRoot. From there you can use the useUndo hook that will return a callback that will undo the last state change. The library is written in typescript and ts support work out of the box.

import React from 'react';
import { RecoilRoot, atom, useRecoilState } from 'recoil';
import { RecoilUndoRoot, useUndo, useRedo } from 'recoil-undo';

const COUNT = atom({
  default: 0,
  key: 'count',
});

const App = () => {
  return (
    <RecoilRoot>
      <RecoilUndoRoot>
        <Counter />
      </RecoilUndoRoot>
    </RecoilRoot>
  );
};

function Counter() {
  const [count, setCount] = useRecoilState(COUNT);
  const undo = useUndo();
  const redo = useRedo();
  return (
    <div>
      <div>
        <button onClick={() => setCount((count) => count - 1)}>-</button>
        {count}
        <button onClick={() => setCount((count) => count + 1)}>+</button>
      </div>
      <button onClick={undo}>Undo</button>
      <button onClick={redo}>Redo</button>
    </div>
  );
}

This component is exported from recoil-undo and should be placed right under the RecoilRoot provider in the application. It is responsible for keeping track of the undo history from your recoil state. At the moment it takes a few optional properties:

• trackedAtoms which is an array of RecoilState (the value that is returned from atom in recoil). If trackedAtoms is passed into RecoilUndoRoot the undo stack will only apply to the atoms provided, all other atoms will be ignored when undoing / redoing. Note: there is no reason to track selectors, as their values will be updated as the atoms change.
• trackingByDefault which is a boolean value (default is true) where you can skip history tracking if required

If trackedAtoms is not passed to RecoilUndoState all atoms will be tracked by recoil-undo.

This hook returns a function that when called will move all tracked atoms to the previous history state.

This hook returns a function that when called will move all tracked atoms to the next history state.

This hook returns an object with two properties startBatch and endBatch. There are many situations where you might want to turn mutliple user interactions into a single item in the undo stack. Example: suppose a user is dragging an object across the screen, you don't want to record every mouse move as an undoable operation. Instead, you only want to record the start and end position on the undo stack. In cases like these, you can call startBatch and endBatch to make sure multiple atom updates only add a single item to the undo stack.

const { startBatch, endBatch } = useBatching();

const onMouseDown = () => {
  startBatch();
};

const onMouseMove = () => {
  // Update item position
};

const onMouseUp = () => {
  endBatch();
};

This will start / stop tracking history if required.

const {getIsTrackingHistory, setIsTrackingHistory} = useIsTrackingHistory();

// getIsTrackingHistory() === false
setIsTrackingHistory(true);
// ... after a re-render
// getIsTrackingHistory() === true

• Undo scoping (keep multiple undo stacks in a single application)

MIT © SawyerHood