reactive-react-redux

by dai-shi

React Redux binding with React Hooks and Proxy

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reactive-react-redux

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React Redux binding with React Hooks and Proxy

If you are looking for a non-Redux library, please visit react-tracked which has the same hooks API.

Introduction

This is a library to bind React and Redux with Hooks API. It has mostly the same API as the official react-redux Hooks API, so it can be used as a drop-in replacement if you are using only basic functionality.

There are two major features in this library that are not in the official react-redux.

1. useTrackedState hook

This library provides another hook

useTrackedState
which is a simpler API than already simple
useSelector
. It returns an entire state, but the library takes care of optimization of re-renders. Most likely,
useTrackedState
performs better than
useSelector
without perfectly tuned selectors.

Technically,

useTrackedState
has no stale props issue.

2. state-based object for context value

react-redux v7 uses store-based object for context value, while react-redux v6 used to use state-based object. Using state-based object naively has unable-to-bail-out issue, but this library uses state-based object with undocumented function

calculateChangedBits
to stop propagation of re-renders. See #29 for details.

How tracking works

A hook

useTrackedState
returns an entire Redux state object with Proxy, and it keeps track of which properties of the object are used in render. When the state is updated, this hook checks whether used properties are changed. Only if it detects changes in the state, it triggers a component to re-render.

Install

npm install reactive-react-redux

Usage (useTrackedState)

import React from 'react';
import { createStore } from 'redux';
import {
  Provider,
  useDispatch,
  useTrackedState,
} from 'reactive-react-redux';

const initialState = { count: 0, text: 'hello', };

const reducer = (state = initialState, action) => { switch (action.type) { case 'increment': return { ...state, count: state.count + 1 }; case 'decrement': return { ...state, count: state.count - 1 }; case 'setText': return { ...state, text: action.text }; default: return state; } };

const store = createStore(reducer);

const Counter = () => { const state = useTrackedState(); const dispatch = useDispatch(); return (

{Math.random()}
Count: {state.count} dispatch({ type: 'increment' })}>+1 dispatch({ type: 'decrement' })}>-1
); };

const TextBox = () => { const state = useTrackedState(); const dispatch = useDispatch(); return (

{Math.random()}
Text: {state.text} dispatch({ type: 'setText', text: event.target.value })} />
); };

const App = () => (

Counter

TextBox

);

API

This library exports four functions. The first three

Provider
,
useDispatch
and
useSelector
are compatible with react-redux hooks. The last
useTrackedState
is unique in this library.

Provider

This is a provider component. Typically, it's used closely in the app root component.

const store = createStore(...);
const App = () => (
  
    ...
  
);

useDispatch

This is a hook that returns

store.dispatch
.
const Component = () => {
  const dispatch = useDispatch();
  // ...
};

useSelector

This is a hook that returns a selected value from a state. This is compatible with react-redux's useSelector. It also supports equalityFn.

const Component = () => {
  const selected = useSelector(selector);
  // ...
};

useTrackedState

This is a hook that returns a whole state wraped by proxies. It detects the usage of the state and record it. It will only trigger re-render if the used part is changed. There are some caveats.

const Component = () => {
  const state = useTrackedState();
  // ...
};

getUntrackedObject

There are some cases when we need to get an original object instead of a tracked object. Although it's not a recommended pattern, the library exports a function as an escape hatch.

const Component = () => {
  const state = useTrackedState();
  const dispatch = useUpdate();
  const onClick = () => {
    // this leaks a proxy outside render
    dispatch({ type: 'FOO', value: state.foo });

// this works as expected
dispatch({ type: 'FOO', value: getUntrackedObject(state.foo) });

}; // ... };

memo

Using

React.memo
with tracked state is not compatible, because
React.memo
stops state access, thus no tracking occurs. This is a special memo to be used instead of
React.memo
with tracking support.
const ChildComponent = memo(({ obj1, obj2 }) => {
  // ...
});

Recipes

useTrackedSelector

You can create a selector hook with tracking support.

import { useTrackedState } from 'reactive-react-redux';

export const useTrackedSelector = selector => selector(useTrackedState());

Please refer this issue for more information.

useTracked

You can combine useTrackedState and useDispatch to make a hook that returns a tuple like

useReducer
.
import { useTrackedState, useDispatch } from 'reactive-react-redux';

export const useTracked = () => { const state = useTrackedState(); const dispatch = useDispatch(); return useMemo(() => [state, dispatch], [state, dispatch]); };

Caveats

Proxy and state usage tracking may not work 100% as expected. There are some limitations and workarounds.

Proxied states are referentially equal only in per-hook basis

const state1 = useTrackedState();
const state2 = useTrackedState();
// state1 and state2 is not referentially equal
// even if the underlying redux state is referentially equal.

You should use

useTrackedState
only once in a component.

An object referential change doesn't trigger re-render if an property of the object is accessed in previous render

const state = useTrackedState();
const { foo } = state;
return ;

const Child = React.memo(({ foo }) => { // ... }; // if foo doesn't change, Child won't render, so foo.id is only marked as used. // it won't trigger Child to re-render even if foo is changed.

You need to use a special

memo
provided by this library.
import { memo } from 'reactive-react-redux';

const Child = memo(({ foo }) => { // ... };

Proxied state might behave unexpectedly outside render

Proxies are basically transparent, and it should behave like normal objects. However, there can be edge cases where it behaves unexpectedly. For example, if you console.log a proxied value, it will display a proxy wrapping an object. Notice, it will be kept tracking outside render, so any prorerty access will mark as used to trigger re-render on updates.

useTrackedState will unwrap a Proxy before wrapping with a new Proxy, hence, it will work fine in usual use cases. There's only one known pitfall: If you wrap proxied state with your own Proxy outside the control of useTrackedState, it might lead memory leaks, because useTrackedState wouldn't know how to unwrap your own Proxy.

To work around such edge cases, the first option is to use primitive values.

const state = useTrackedState();
const dispatch = useUpdate();
dispatch({ type: 'FOO', value: state.fooObj }); // Instead of using objects,
dispatch({ type: 'FOO', value: state.fooStr }); // Use primitives.

The second option is to use

getUntrackedObject
.
import { getUntrackedObject } from 'react-tracked';
dispatch({ type: 'FOO', value: getUntrackedObject(state.fooObj) });

You could implement a special dispatch function to do this automatically.

Examples

The examples folder contains working examples. You can run one of them with

PORT=8080 npm run examples:01_minimal

and open http://localhost:8080 in your web browser.

You can also try them in codesandbox.io: 01 02 03 04 05 06 07 08 09 11 12 13

Benchmarks

benchmark result

See #32 for details.

Blogs

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