Redux Wrapper for Next.js

It is just a publish of fix branch from https://github.com/fostyfost/next-redux-wrapper

A HOC that brings Next.js and Redux together

:warning: The current version of this library only works with Next.js 9.3 and newer. If you are required to use Next.js 6-9 you can use version 3-5 of this library, see branches. Otherwise, consider upgrading Next.js. :warning:

Contents:

• Motivation
• Installation
• Usage
  • State reconciliation during hydration
  • Configuration
  • getStaticProps
  • getServerSideProps
  • Page.getInitialProps
  • App
  • App and getServerSideProps or getStaticProps at page level
• How it works
• Tips and Tricks
  • Server and Client state separation
  • Document
  • Error Pages
  • Async actions
  • Custom serialization and deserialization
  • Usage with Redux Saga
  • Usage with Redux Persist
• Upgrade from 5.x to 6.x
• Upgrade from 1.x to 2.x
• Resources

Motivation

Setting up Redux for static apps is rather simple: a single Redux store has to be created that is provided to all pages.

When Next.js static site generator or server side rendering is involved, however, things start to get complicated as another store instance is needed on the server to render Redux-connected components.

Furthermore, access to the Redux Store may also be needed during a page's getInitialProps.

This is where next-redux-wrapper comes in handy: It automatically creates the store instances for you and makes sure they all have the same state.

Moreover it allows to properly handle complex cases like App.getInitialProps (when using pages/_app) together with getStaticProps or getServerSideProps at individual page level.

Library provides uniform interface no matter in which Next.js lifecycle method you would like to use the Store.

Installation

npm install next-redux-wrapper react-redux --save

Note that next-redux-wrapper requires react-redux as peer dependency.

Usage

Live example: https://codesandbox.io/s/next-redux-wrapper-demo-7n2t5.

All examples are written in TypeScript. If you're using plain JavaScript just omit type declarations.

Next.js has several data fetching mechanisms, this library can attach to any of them. But first you have to write some common code.

Please note that your reducer must have the HYDRATE action handler. HYDRATE action handler must properly reconciliate the hydrated state on top of the existing state (if any). This behavior was added in version 6 of this library. We'll talk about this special action later.

Create a file named store.ts:

// store.ts

import {createStore, AnyAction} from 'redux';
import {MakeStore, createWrapper, Context, HYDRATE} from 'next-redux-wrapper';

export interface State {
    tick: string;
}

// create your reducer
const reducer = (state: State = {tick: 'init'}, action: AnyAction) => {
    switch (action.type) {
        case HYDRATE:
            // Attention! This will overwrite client state! Real apps should use proper reconciliation.
            return {...state, ...action.payload};
        case 'TICK':
            return {...state, tick: action.payload};
        default:
            return state;
    }
};

// create a makeStore function
const makeStore: MakeStore<State> = (context: Context) => createStore(reducer);

// export an assembled wrapper
export const wrapper = createWrapper<State>(makeStore, {debug: true});

// store.ts

import {createStore} from 'redux';
import {createWrapper, HYDRATE} from 'next-redux-wrapper';

// create your reducer
const reducer = (state = {tick: 'init'}, action) => {
    switch (action.type) {
        case HYDRATE:
            return {...state, ...action.payload};
        case 'TICK':
            return {...state, tick: action.payload};
        default:
            return state;
    }
};

// create a makeStore function
const makeStore = context => createStore(reducer);

// export an assembled wrapper
export const wrapper = createWrapper(makeStore, {debug: true});

It is highly recommended to use pages/_app to wrap all pages at once, otherwise due to potential race conditions you may get Cannot update component while rendering another component:

import React, {FC} from 'react';
import {AppProps} from 'next/app';
import {wrapper} from '../components/store';

const WrappedApp: FC<AppProps> = ({Component, pageProps}) => (
    <Component {...pageProps} />
);

export default wrapper.withRedux(WrappedApp);

import React from 'react';
import {wrapper} from '../components/store';

const MyApp = ({Component, pageProps}) => (
    <Component {...pageProps} />
);

export default wrapper.withRedux(MyApp);

:warning: Next.js provides generic getInitialProps when using class MyApp extends App which will be picked up by wrapper, so you must not extend App as you'll be opted out of Automatic Static Optimization: https://err.sh/next.js/opt-out-auto-static-optimization. Just export a regular Functional Component as in the example above.

State reconciliation during hydration

Each time when pages that have getStaticProps or getServerSideProps are opened by user the HYDRATE action will be dispatched. This may happen during initial page load and during regular page navigation. The payload of this action will contain the state at the moment of static generation or server side rendering, so your reducer must merge it with existing client state properly.

Simplest way is to use server and client state separation.

Another way is to use https://github.com/benjamine/jsondiffpatch to analyze diff and apply it properly:

import {HYDRATE} from 'next-redux-wrapper';

// create your reducer
const reducer = (state = {tick: 'init'}, action) => {
    switch (action.type) {
        case HYDRATE:
            const stateDiff = diff(state, action.payload) as any;
            const wasBumpedOnClient = stateDiff?.page?.[0]?.endsWith('X'); // or any other criteria
            return {
                ...state,
                ...action.payload,
                page: wasBumpedOnClient ? state.page : action.payload.page, // keep existing state or use hydrated
            };
        case 'TICK':
            return {...state, tick: action.payload};
        default:
            return state;
    }
};

Or like this (from with-redux-wrapper example in Next.js repo):

const reducer = (state, action) => {
  if (action.type === HYDRATE) {
    const nextState = {
      ...state, // use previous state
      ...action.payload, // apply delta from hydration
    }
    if (state.count) nextState.count = state.count // preserve count value on client side navigation
    return nextState
  } else {
    return combinedReducer(state, action)
  }
}

Configuration

The createWrapper function accepts makeStore as its first argument. The makeStore function should return a new Redux Store instance each time it's called. No memoization is needed here, it is automatically done inside the wrapper.

createWrapper also optionally accepts a config object as a second parameter:

• storeKey (optional, string) : the key used on window to persist the store on the client
• debug (optional, boolean) : enable debug logging
• serializeState and deserializeState: custom functions for serializing and deserializing the redux state, see Custom serialization and deserialization.

When makeStore is invoked it is provided with a Next.js context, which could be NextPageContext or AppContext or getStaticProps or getServerSideProps context depending on which lifecycle function you will wrap.

Some of those contexts (getServerSideProps always, and NextPageContext, AppContext sometimes if page is rendered on server) can have request and response related properties:

• req (IncomingMessage)
• res (ServerResponse)

Although it is possible to create server or client specific logic in both makeStore, I highly recommend that they do not have different behavior. This may cause errors and checksum mismatches which in turn will ruin the whole purpose of server rendering.

getStaticProps

This section describes how to attach to getStaticProps lifecycle function.

Let's create a page in pages/pageName.tsx:

import React from 'react';
import {NextPage} from 'next';
import {Provider, useSelector} from 'react-redux';
import {wrapper, State} from '../store';

export const getStaticProps = wrapper.getStaticProps(
    ({store, preview}) => {
        console.log('2. Page.getStaticProps uses the store to dispatch things');
        store.dispatch({type: 'TICK', payload: 'was set in other page ' + preview});
    }
);

// you can also use `connect()` instead of hooks
const Page: NextPage = () => {
    const {tick} = useSelector<State, State>(state => state);
    return (
        <div>{tick}</div>
    );
};

export default Page;

import React from 'react';
import {Provider, useSelector} from 'react-redux';
import {wrapper} from '../store';

export const getStaticProps = wrapper.getStaticProps(
    ({store, preview}) => {
        console.log('2. Page.getStaticProps uses the store to dispatch things');
        store.dispatch({type: 'TICK', payload: 'was set in other page ' + preview});
    }
);

// you can also use `connect()` instead of hooks
const Page = () => {
    const {tick} = useSelector(state => state);
    return (
        <div>{tick}</div>
    );
};

export default Page;

:warning: Each time when pages that have getStaticProps are opened by user the HYDRATE action will be dispatched. The payload of this action will contain the state at the moment of static generation, it will not have client state, so your reducer must merge it with existing client state properly. More about this in Server and Client State Separation.

Although you can wrap individual pages (and not wrap the pages/_app) it is not recommended, see last paragraph in usage section.

getServerSideProps

This section describes how to attach to getServerSideProps lifecycle function.

Let's create a page in pages/pageName.tsx:

import React from 'react';
import {NextPage} from 'next';
import {Provider, connect} from 'react-redux';
import {wrapper, State} from '../store';

export const getServerSideProps = wrapper.getServerSideProps(
    ({store, req, res, ...etc}) => {
        console.log('2. Page.getServerSideProps uses the store to dispatch things');
        store.dispatch({type: 'TICK', payload: 'was set in other page'});
    }
);

// Page itself is not connected to Redux Store, it has to render Provider to allow child components to connect to Redux Store
const Page: NextPage<State> = ({tick}) => (
    <div>{tick}</div>
);

// you can also use Redux `useSelector` and other hooks instead of `connect()`
export default connect((state: State) => state)(Page);

import React from 'react';
import {Provider, connect} from 'react-redux';
import {wrapper} from '../store';

export const getServerSideProps = wrapper.getServerSideProps(
    ({store, req, res, ...etc}) => {
        console.log('2. Page.getServerSideProps uses the store to dispatch things');
        store.dispatch({type: 'TICK', payload: 'was set in other page'});
    }
);

// Page itself is not connected to Redux Store, it has to render Provider to allow child components to connect to Redux Store
const Page = ({tick}) => (
    <div>{tick}</div>
);

// you can also use Redux `useSelector` and other hooks instead of `connect()`
export default connect(state => state)(Page);

:warning: Each time when pages that have getServerSideProps are opened by user the HYDRATE action will be dispatched. The payload of this action will contain the state at the moment of server side rendering, it will not have client state, so your reducer must merge it with existing client state properly. More about this in Server and Client State Separation.

Although you can wrap individual pages (and not wrap the pages/_app) it is not recommended, see last paragraph in usage section.

Page.getInitialProps

import React, {Component} from 'react';
import {NextPage} from 'next';
import {wrapper, State} from '../store';

// you can also use `connect()` instead of hooks
const Page: NextPage = () => {
    const {tick} = useSelector<State, State>(state => state);
    return (
        <div>{tick}</div>
    );
};

Page.getInitialProps = ({store, pathname, req, res}) => {
    console.log('2. Page.getInitialProps uses the store to dispatch things');
    store.dispatch({type: 'TICK', payload: 'was set in error page ' + pathname});
};

export default Page;

import React, {Component} from 'react';
import {wrapper} from '../store';

// you can also use `connect()` instead of hooks
const Page = () => {
    const {tick} = useSelector(state => state);
    return (
        <div>{tick}</div>
    );
};

Page.getInitialProps = ({store, pathname, req, res}) => {
    console.log('2. Page.getInitialProps uses the store to dispatch things');
    store.dispatch({type: 'TICK', payload: 'was set in error page ' + pathname});
};

export default Page;

Keep in mind that req and res may not be available if getInitialProps is called on client side.

Stateless function component also can be replaced with class:

class Page extends Component {

    public static getInitialProps = () => { ... };

    render() {
        // stuff
    }
}

export default Page;

Although you can wrap individual pages (and not wrap the pages/_app) it is not recommended, see last paragraph in usage section.

App

:warning: You can dispatch actions from the pages/_app too. But this mode is not compatible with Next.js 9's Auto Partial Static Export feature, see the explanation below.

The wrapper can also be attached to your _app component (located in /pages). All other components can use the connect function of react-redux.

# pages/_app.tsx

import React from 'react';
import App, {AppInitialProps, AppContext} from 'next/app';
import {wrapper} from '../components/store';
import {State} from '../components/reducer';

class MyApp extends App<AppInitialProps> {

    public static getInitialProps = async ({Component, ctx}: AppContext) => {

        ctx.store.dispatch({type: 'TOE', payload: 'was set in _app'});

        return {
            pageProps: {
                // Call page-level getInitialProps
                ...(Component.getInitialProps ? await Component.getInitialProps(ctx) : {}),
                // Some custom thing for all pages
                pathname: ctx.pathname,
            },
        };

    };

    public render() {
        const {Component, pageProps} = this.props;

        return (
            <Component {...pageProps} />
        );
    }
}

export default wrapper.withRedux(MyApp);

# pages/_app.tsx

import React from 'react';
import App from 'next/app';
import {wrapper} from '../components/store';

class MyApp extends App {

    public static getInitialProps = async ({Component, ctx}) => {

        ctx.store.dispatch({type: 'TOE', payload: 'was set in _app'});

        return {
            pageProps: {
                // Call page-level getInitialProps
                ...(Component.getInitialProps ? await Component.getInitialProps(ctx) : {}),
                // Some custom thing for all pages
                pathname: ctx.pathname,
            },
        };

    };

    public render() {
        const {Component, pageProps} = this.props;

        return (
            <Component {...pageProps} />
        );
    }
}

export default wrapper.withRedux(MyApp);

And then all pages can simply be connected (the example considers page components):

// pages/xxx.tsx

import React from "react";
import {NextPage} from 'next';
import {connect} from "react-redux";
import {NextPageContext} from "next";
import {State} from "../store";

const Page:NextPage<State> = ({foo, custom}) => (
    <div>
        <div>Prop from Redux {foo}</div>
        <div>Prop from getInitialProps {custom}</div>
    </div>
);

// No need to wrap pages if App was wrapped
Page.getInitialProps = ({store, pathname, query}: NextPageContext) => {
    store.dispatch({type: 'FOO', payload: 'foo'}); // The component can read from the store's state when rendered
    return {custom: 'custom'}; // You can pass some custom props to the component from here
}

export default connect((state: State) => state)(Page);

// pages/xxx.tsx

import React from "react";
import {connect} from "react-redux";

const Page = ({foo, custom}) => (
    <div>
        <div>Prop from Redux {foo}</div>
        <div>Prop from getInitialProps {custom}</div>
    </div>
);

// No need to wrap pages if App was wrapped
Page.getInitialProps = ({store, pathname, query}) => {
    store.dispatch({type: 'FOO', payload: 'foo'}); // The component can read from the store's state when rendered
    return {custom: 'custom'}; // You can pass some custom props to the component from here
}

export default connect((state: State) => state)(Page);

App and getServerSideProps or getStaticProps at page level

You can also use getServerSideProps or getStaticProps at page level, in this case HYDRATE action will be dispatched twice: with state after App.getInitialProps and then with state after getServerSideProps or getStaticProps:

• If you use getServerSideProps at page level then store in getServerSideProps will be executed after App.getInitialProps and will have state from it, so second HYDRATE will have full state from both
• :warning: If you use getStaticProps at page level then store in getStaticProps will be executed at compile time and will NOT have state from App.getInitialProps because they are executed in different contexts and state cannot be shared. First HYDRATE actions state after App.getInitialProps and second will have state after getStaticProps (even though it was executed earlier in time).

Simplest way to ensure proper merging is to drop initial values from action.payload:

const reducer = (state: State = {app: 'init', page: 'init'}, action: AnyAction) => {
    switch (action.type) {
        case HYDRATE:
            if (action.payload.app === 'init') delete action.payload.app;
            if (action.payload.page === 'init') delete action.payload.page;
            return {...state, ...action.payload};
        case 'APP':
            return {...state, app: action.payload};
        case 'PAGE':
            return {...state, page: action.payload};
        default:
            return state;
    }
};

const reducer = (state = {app: 'init', page: 'init'}, action) => {
    switch (action.type) {
        case HYDRATE:
            if (action.payload.app === 'init') delete action.payload.app;
            if (action.payload.page === 'init') delete action.payload.page;
            return {...state, ...action.payload};
        case 'APP':
            return {...state, app: action.payload};
        case 'PAGE':
            return {...state, page: action.payload};
        default:
            return state;
    }
};

Assume page only dispatches PAGE actiona and App only APP, this makes state merging safe.

More about that in Server and Client state separation.

How it works

Using next-redux-wrapper ("the wrapper"), the following things happen on a request:

• Phase 1: getInitialProps/getStaticProps/getServerSideProps

  • The wrapper creates a server-side store (using makeStore) with an empty initial state. In doing so it also provides the Request and Response objects as options to makeStore.
  • In App mode:
    • The wrapper calls the _app's getInitialProps function and passes the previously created store.
    • Next.js takes the props returned from the _app's getInitialProps method, along with the store's state.
  • In per-page mode:
    • The wrapper calls the Page's getXXXProps function and passes the previously created store.
    • Next.js takes the props returned from the Page's getXXXProps method, along with the store's state.

• Phase 2: SSR

  • The wrapper creates a new store using makeStore
  • The wrapper dispatches HYDRATE action with the previous store's state as payload
  • That store is passed as a property to the _app or page component.
  • Connected components may alter the store's state, but the modified state will not be transferred to the client.

• Phase 3: Client

  • The wrapper creates a new store
  • The wrapper dispatches HYDRATE action with the state from Phase 1 as payload
  • That store is passed as a property to the _app or page component.
  • The wrapper persists the store in the client's window object, so it can be restored in case of HMR.

Note: The client's state is not persisted across requests (i.e. Phase 1 always starts with an empty state). Hence, it is reset on page reloads. Consider using Redux persist if you want to persist state between requests.

Tips and Tricks

Server and Client state separation

Each time when pages that have getStaticProps or getServerSideProps are opened by user the HYDRATE action will be dispatched. The payload of this action will contain the state at the moment of static generation or server side rendering, so your reducer must merge it with existing client state properly.

The easiest and most stable way to make sure nothing is accidentally overwritten is to make sure that your reducer applies client side and server side actions to different substates of your state and they never clash:

export interface State {
    server: any;
    client: any;
}

const reducer = (state: State = {tick: 'init'}, action: AnyAction) => {
    switch (action.type) {
        case HYDRATE:
            return {
                ...state,
                server: {
                    ...state.server,
                    ...action.payload.server
                }
            }
        case 'SERVER_ACTION':
            return {
                ...state,
                server: {
                    ...state.server,
                    tick: action.payload
                }
            };
        case 'CLIENT_ACTION':
            return {
                ...state,
                client: {
                    ...state.client,
                    tick: action.payload
                }
            };
        default:
            return state;
    }
};

const reducer = (state = {tick: 'init'}, action) => {
    switch (action.type) {
        case HYDRATE:
            return {
                ...state,
                server: {
                    ...state.server,
                    ...action.payload.server
                }
            }
        case 'SERVER_ACTION':
            return {
                ...state,
                server: {
                    ...state.server,
                    tick: action.payload
                }
            };
        case 'CLIENT_ACTION':
            return {
                ...state,
                client: {
                    ...state.client,
                    tick: action.payload
                }
            };
        default:
            return state;
    }
};

Also you can use a library like https://github.com/benjamine/jsondiffpatch to analyze diff and apply it properly.

Document

I don't recommend using withRedux in pages/_document.js, Next.JS does not provide a reliable way to determine the sequence when components will be rendered. So per Next.JS recommendation it is better to have just data-agnostic things in pages/_document.

Error Pages

Error pages can also be wrapped the same way as any other pages.

Transition to an error page (pages/_error.js template) will cause pages/_app.js to be applied but it is always a full page transition (not HTML5 pushState), so client will have the store created from scratch using state from the server. So unless you persist the store on the client somehow the resulting previous client state will be ignored.

Async actions

You need to install https://github.com/pburtchaell/redux-promise-middleware in order to dispatch Promises as async actions. Follow the installation guide of the library, then you'll be able to handle it like this:

function someAsyncAction() {
    return {
        type: 'FOO',
        payload: new Promise(resolve => resolve('foo'))
    }
}

async function getInitialProps({store}) {
    await store.dispatch(someAsyncAction());
    return {custom: 'custom'};
}

Custom serialization and deserialization

If you are storing complex types such as Immutable.JS or EJSON objecs in your state, a custom serialize and deserialize handler might be handy to serialize the redux state on the server and derserialize it again on the client. To do so, provide serializeState and deserializeState as config options to withRedux.

The reason is that state snapshot is transferred over the network from server to client as a plain object.

Example of a custom serialization of an Immutable.JS state using json-immutable:

const {serialize, deserialize} = require('json-immutable');

createWrapper({
    serializeState: state => serialize(state),
    deserializeState: state => deserialize(state)
});

Same thing using Immutable.JS:

const {fromJS} = require('immutable');

createWrapper({
    serializeState: state => state.toJS(),
    deserializeState: state => fromJS(state),
});

Usage with Redux Saga

[Note, this method may be unsafe - make sure you put a lot of thought into handling async sagas correctly. Race conditions happen very easily if you aren't careful.] To utilize Redux Saga, one simply has to make some changes to their makeStore function. Specifically, redux-saga needs to be initialized inside this function, rather than outside of it. (I did this at first, and got a nasty error telling me Before running a Saga, you must mount the Saga middleware on the Store using applyMiddleware). Here is how one accomplishes just that. This is just slightly modified from the setup example at the beginning of the docs. Keep in mind that this setup will opt you out of Automatic Static Optimization: https://err.sh/next.js/opt-out-auto-static-optimization.

Create your root saga as usual, then implement the store creator:

import {createStore, applyMiddleware, Store} from 'redux';
import {MakeStore, createWrapper, Context} from 'next-redux-wrapper';
import createSagaMiddleware, {Task} from 'redux-saga';
import reducer, {State} from './reducer';
import rootSaga from './saga';

export interface SagaStore extends Store {
    sagaTask?: Task;
}

export const makeStore: MakeStore<State> = (context: Context) => {
    // 1: Create the middleware
    const sagaMiddleware = createSagaMiddleware();

    // 2: Add an extra parameter for applying middleware:
    const store = createStore(reducer, applyMiddleware(sagaMiddleware));

    // 3: Run your sagas on server
    (store as SagaStore).sagaTask = sagaMiddleware.run(rootSaga);

    // 4: now return the store:
    return store;
};

export const wrapper = createWrapper<State>(makeStore, {debug: true});

import {createStore, applyMiddleware} from 'redux';
import {createWrapper} from 'next-redux-wrapper';
import createSagaMiddleware from 'redux-saga';
import reducer from './reducer';
import rootSaga from './saga';

export const makeStore = (context) => {
    // 1: Create the middleware
    const sagaMiddleware = createSagaMiddleware();

    // 2: Add an extra parameter for applying middleware:
    const store = createStore(reducer, applyMiddleware(sagaMiddleware));

    // 3: Run your sagas on server
    (store as SagaStore).sagaTask = sagaMiddleware.run(rootSaga);

    // 4: now return the store:
    return store;
};

export const wrapper = createWrapper(makeStore, {debug: true});

Using pages/_app

Then in the pages/_app wait stop saga and wait for it to finish when execution is on server:

import React from 'react';
import App, {AppInitialProps, AppContext} from 'next/app';
import {END} from 'redux-saga';
import {SagaStore, wrapper} from '../components/store';

class WrappedApp extends App<AppInitialProps> {
    public static getInitialProps = async ({Component, ctx}: AppContext) => {
        // 1. Wait for all page actions to dispatch
        const pageProps = {
            ...(Component.getInitialProps ? await Component.getInitialProps(ctx) : {}),
        };

        // 2. Stop the saga if on server
        if (ctx.req) {
            ctx.store.dispatch(END);
            await (ctx.store as SagaStore).sagaTask.toPromise();
        }

        // 3. Return props
        return {
            pageProps,
        };
    };

    public render() {
        const {Component, pageProps} = this.props;
        return <Component {...pageProps} />;
    }
}

export default wrapper.withRedux(WrappedApp);

import React from 'react';
import App from 'next/app';
import {END} from 'redux-saga';
import {SagaStore, wrapper} from '../components/store';

class WrappedApp extends App {
    public static getInitialProps = async ({Component, ctx}) => {
        // 1. Wait for all page actions to dispatch
        const pageProps = {
            ...(Component.getInitialProps ? await Component.getInitialProps(ctx) : {}),
        };

        // 2. Stop the saga if on server
        if (ctx.req) {
            ctx.store.dispatch(END);
            await (ctx.store as SagaStore).sagaTask.toPromise();
        }

        // 3. Return props
        return {
            pageProps,
        };
    };

    public render() {
        const {Component, pageProps} = this.props;
        return <Component {...pageProps} />;
    }
}

export default wrapper.withRedux(WrappedApp);

Using getServerSideProps or getStaticProps

In order to use it with getServerSideProps or getStaticProps you need to await for sagas in each page's handler:

export const getServerSideProps = ReduxWrapper.getServerSideProps(
  async ({ store, req, res, ...etc }) => {
    // regular stuff
    store.dispatch(ApplicationSlice.actions.updateConfiguration());
    // end the saga
    store.dispatch(END);
    await store.sagaTask.toPromise();
  }
);

Usage without getInitialProps inside _app

If you don't want to opt-out of automatic pre-rendering in your Next.js app, you can manage server-called sagas on a per page basis like the official Next.js "with Redux Saga" example does. If you do go with this option, please ensure that you await any and all sagas within any Next.js page methods. If you miss it on one of pages you'll end up with inconsistent sate being sent to client. So, we consider waiting in _app to be automatically safer, but obviously the main drawback is opting out of automatic static exports.

Usage with Redux Persist

Boilerplate: https://github.com/fazlulkarimweb/with-next-redux-wrapper-redux-persist

Honestly, I think that putting a persistence gate is not necessary because the server can already send some HTML with some state, so it's better to show it right away and then wait for REHYDRATE action to happen to show additional delta coming from persistence storage. That's why we use Server Side Rendering in the first place.

But, for those who actually want to block the UI while rehydration is happening, here is the solution (still hacky though):

// lib/redux.js
import logger from 'redux-logger';
import {applyMiddleware, createStore} from 'redux';

const SET_CLIENT_STATE = 'SET_CLIENT_STATE';

export const reducer = (state, {type, payload}) => {
    // Usual stuff with HYDRATE handler
    if (type === SET_CLIENT_STATE) {
        return {
            ...state,
            fromClient: payload
        };
    }
    return state;
};

const makeConfiguredStore = (reducer) =>
    createStore(reducer, undefined, applyMiddleware(logger));

const makeStore = () => {

    const isServer = typeof window === 'undefined';

    if (isServer) {

        return makeConfiguredStore(reducer);

    } else {

        // we need it only on client side
        const {persistStore, persistReducer} = require('redux-persist');
        const storage = require('redux-persist/lib/storage').default;

        const persistConfig = {
            key: 'nextjs',
            whitelist: ['fromClient'], // make sure it does not clash with server keys
            storage
        };

        const persistedReducer = persistReducer(persistConfig, reducer);
        const store = makeConfiguredStore(persistedReducer);

        store.__persistor = persistStore(store); // Nasty hack

        return store;
    }
};

export const wrapper = createWrapper(makeStore);

export const setClientState = (clientState) => ({
    type: SET_CLIENT_STATE,
    payload: clientState
});

And then in Next.js _app page you can use bare context access to get the store (https://react-redux.js.org/api/provider#props):

// pages/_app.tsx
import React from "react";
import App from "next/app";
import {ReactReduxContext} from 'react-redux'
import {wrapper} from "./lib/redux";
import {PersistGate} from 'redux-persist/integration/react';

export default wrapper.withRedux(class MyApp extends App {
    render() {
        const {Component, pageProps} = this.props;
        return (
            <ReactReduxContext.Consumer>
                {({ store }) => {
                    <PersistGate persistor={store.__persistor} loading={<div>Loading</div>}>
                        <Component {...pageProps} />
                    </PersistGate>
                }}
            </ReactReduxContext.Consumer>
        );
    }
});

Or using hooks:

// pages/_app.tsx
import React from "react";
import App from "next/app";
import {useStore} from 'react-redux'
import {wrapper} from "./lib/redux";
import {PersistGate} from 'redux-persist/integration/react';

export default wrapper.withRedux(({Component, pageProps}) => {
    const store = useStore();
    return (
        <PersistGate persistor={store.__persistor} loading={<div>Loading</div>}>
            <Component {...pageProps} />
        </PersistGate>
    );
});

And then in Next.js page:

// pages/index.js
import React from "react";
import {connect} from "react-redux";

export default connect(
    (state) => state,
    {setClientState}
)(({fromServer, fromClient, setClientState}) => (
    <div>
        <div>fromServer: {fromServer}</div>
        <div>fromClient: {fromClient}</div>
        <div><button onClick={e => setClientState('bar')}>Set Client State</button></div>
    </div>
));

Upgrade from 5.x to 6.x

Major change in the way how things are wrapped in version 6.

1. Default export withRedux is marked deprecated, you should create a wrapper const wrapper = createWrapper(makeStore, {debug: true}) and then use wrapper.withRedux(MyApp).

2. Your makeStore function no longer gets initialState, it only receives the context: makeStore(context: Context). Context could be NextPageContext or AppContext or getStaticProps or getServerSideProps context depending on which lifecycle function you will wrap. Instead, you need to handle the HYDRATE action in the reducer. The payload of this action will contain the state at the moment of static generation or server side rendering, so your reducer must merge it with existing client state properly.

3. App should no longer wrap its children with Provider, it is now done internally.

4. isServer is not passed in context/props, use your own function or simple check const isServer = typeof window === 'undefined' or !!context.req or !!context.ctx.req.

5. store is not passed to wrapped component props.

6. WrappedAppProps was renamed to WrapperProps.

Upgrade from 1.x to 2.x

If your project was using Next.js 5 and Next Redux Wrapper 1.x these instructions will help you to upgrade to 2.x.

1. Upgrade Next.js and Wrapper

   $ npm install next@6 --save-dev
   $ npm install next-redux-wrapper@latest --save

2. Replace all usages of import withRedux from "next-redux-wrapper"; and withRedux(...)(WrappedComponent) in all your pages with plain React Redux connect HOC:

   import {connect} from "react-redux";
   
   export default connect(...)(WrappedComponent);

   You also may have to reformat your wrapper object-based config to simple React Redux config.

3. Create the pages/_app.js file with the following minimal code:

   // pages/_app.js
   import React from 'react'
   import {Provider} from 'react-redux';
   import App from 'next/app';
   import {wrapper} from '../store';
   
   class MyApp extends App {
       static async getInitialProps({Component, ctx}) {
           return {
               pageProps: {
                   // Call page-level getInitialProps
                   ...(Component.getInitialProps ? await Component.getInitialProps(ctx) : {}),
               }
           };
       }
   
       render() {
           const {Component, pageProps} = this.props;
           return (
               <Component {...pageProps} />
           );
       }
   
   }
   
   export default wrapper.withRedux(MyApp);

4. Follow Next.js 6 upgrade instructions for all your components (props.router instead of props.url and so on)

That's it. Your project should now work the same as before.

Resources

• next-redux-saga
• How to use with Redux and Redux Saga
• Redux Saga Example: https://gist.github.com/pesakitan22/94b4984140ba0f2c9e52c5289a7d833e.