how to use typescript, next-redux-wrapper, getServerSideProps?

Question

I want JavaScript -> TypeScript! but, so hard.

// store.js

import { applyMiddleware, createStore, compose, Store } from "redux";
import createSagaMiddleware, { Task } from "redux-saga";
import { createWrapper } from "next-redux-wrapper";
import { composeWithDevTools } from "redux-devtools-extension";

import reducer from "./reducers";
import rootSaga from "./sagas";

const configureStore = () => {
  const sagaMiddleware = createSagaMiddleware();
  const middlewares = [sagaMiddleware];
  const enhancer =
    process.env.NODE_ENV === "production"
      ? compose(applyMiddleware(...middlewares))
      : composeWithDevTools(applyMiddleware(...middlewares));
  const store = createStore(reducer, enhancer);
  store.sagaTask = sagaMiddleware.run(rootSaga);
  return store;
};

const wrapper = createWrapper(configureStore, {
  debug: process.env.NODE_ENV === "development",
});

export default wrapper;

// reducers/index.ts

import { HYDRATE } from "next-redux-wrapper";
import { AnyAction, combineReducers } from "redux";

import url, { IUrlReducerState } from "./reducer_url";
import user, { IUserReducerState } from "./reducer_user";

export type State = {
  url: IUrlReducerState;
  user: IUserReducerState;
};

const rootReducer = (state: State, action: AnyAction) => {
  switch (action.type) {
    case HYDRATE:
      return action.payload;

    default: {
      const combineReducer = combineReducers({
        url,
        user,
      });
      return combineReducer(state, action);
    }
  }
};
export type RootState = ReturnType<typeof rootReducer>;
export default rootReducer;

reducers/index.ts <- Is this how you do it? I've changed it a little bit.

// pages/index.js

import { END } from "redux-saga";
import wrapper from "../store";

export const getServerSideProps = wrapper.getServerSideProps(
  async (context) => {

    context.store.dispatch({
      type: LOAD_USER_REQUEST,
    });

    context.store.dispatch(END);
    await context.store.sagaTask.toPromise();
  }
);

I saw the official documentation, but I don't understand: https://github.com/kirill-konshin/next-redux-wrapper#getserversideprops

These codes are not problematic in JavaScript. But there's a problem with TypeScript.

Answer 1

Here are the issues that I see:

1. You will get an error in createStore(reducer, enhancer) because your reducer does not fit the type (state: State | undefined, action: AnyAction) => State. You must make your reducer fit this type. The problem right now is that your reducer does not allow for state to be undefined.

change

const rootReducer = (state: State, action: AnyAction) => {

to

const rootReducer = (state: State | undefined, action: AnyAction): State => {

2. You will get an error on the line store.sagaTask = sagaMiddleware.run(rootSaga); because the store object created by redux does not have a property called sagaTask. There is another discussion about that here.

Here is one solution, based on the next-redux-wrapper docs:

define a new interface for your store which includes the task

export interface SagaStore extends Store<State, AnyAction> {
  sagaTask: Task;
}

replace

store.sagaTask = sagaMiddleware.run(rootSaga);

with

(store as SagaStore).sagaTask = sagaMiddleware.run(rootSaga);

replace

await context.store.sagaTask.toPromise();

with

await (context.store as SagaStore).sagaTask.toPromise();

Answer 2

I also had some bad time in trying to sync Redux with Next in a proper way, and them, using next-redux-wrapper, I created a template of a project, which is currently working and following the guidelines from next-redux-wrapper. You can take a look on that:

https://github.com/felipemeriga/next-typescript-redux-template

Basically I'm created the wrapper like this:

const thunkMiddleware = thunk.withExtraArgument({}) as ThunkMiddleware<IStoreState, AnyAction>;

// create a makeStore function
// This makeStore is needed for the wrapper, for every new page that is called, a new store with the current values will be created
const makeStore: MakeStore<IStoreState> = (context: Context) => createStore(reducers, composeWithDevTools(applyMiddleware(thunkMiddleware)));

export type ExtraArgument = {};

export type ThunkCreator<R = Promise<any>> = ActionCreator<ThunkAction<R, IStoreState, ExtraArgument, AnyAction>>;

// export an assembled wrapper
// this wrapper will be used to every page's component, for injecting the store and actions into it.
const wrapper = createWrapper<IStoreState>(makeStore, {debug: false});

export default wrapper;

Then overrided the _app.tsx:

// For default you don't need to edit _app.tsx, but if you want to wrapper the pages with redux wrapper, you need
// to override _app.tsx with this code bellow
class MyApp extends App {
    // @ts-ignore
    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);

And finally injected in the index.tsx component:

interface IProps {
    tick: ITickState
    updateAnnouncement: any
}

interface IState {}

interface IDispatchProps {
    onUpdateTick: (message: string) => ITickState,
    thunkAsyncFunction: () => Promise<any>;
}

type Props = IProps & IState & IDispatchProps

class App extends React.Component<Props> {

    constructor(props: Props) {
        super(props);
    }

    async componentWillUnmount(): Promise<void> {
        await this.props.thunkAsyncFunction();
    }

    render() {
        return (
            <Layout title="Home | Next.js + TypeScript Example">
                <h1>Hello Next.js </h1>
                <p>
                    <Link href="/about">
                        <a>About</a>
                    </Link>
                </p>
                <div>
                    The current tick state: {this.props.tick.message}
                </div>
            </Layout>
        );
    }
}

const mapStateToProps = (state: IStoreState): {tick: ITickState} => ({
    tick: getTickState(state)
});

const mapDispatchToProps = (dispatch: any): IDispatchProps => {
    return {
        onUpdateTick: (message: string) =>
            dispatch(updateTick(message)),
        thunkAsyncFunction: () => dispatch(thunkAsyncFunction())
    }
};

export default connect(mapStateToProps, mapDispatchToProps)(App);

// As the wrapper is injected in _app.tsx, for every component(page) that will interact with Redux and Thunk
// you need to place this piece of code bellow, that will get the static props from the wrapper, and inject on your
// component
export const getStaticProps = wrapper.getStaticProps(
    ({}) => {
    }
);