Stencil Redux

A simple redux connector for Stencil-built web components inspired by react-redux.

Install

npm install @stencil/redux
npm install redux

Usage

Stencil Redux uses the redux library underneath. Setting up the store and defining actions, reducers, selectors, etc. should be familiar to you if you've used React with Redux.

Configure the Root Reducer

// redux/reducers.ts

import { combineReducers } from 'redux';

// Import feature reducers and state interfaces.
import { TodoState, todos } from './todos/reducers';

// This interface represents app state by nesting feature states.
export interface RootState {
  todos: TodoState;
}

// Combine feature reducers into a single root reducer
export const rootReducer = combineReducers({
  todos,
});

Configure the Actions

// redux/actions.ts

import { RootState } from './reducers';

// Import feature action interfaces
import { TodoAction } from './todos/actions';

// Export all feature actions for easier access.
export * from './todos/actions';

// Combine feature action interfaces into a base type. Use union types to
// combine feature interfaces.
// https://www.typescriptlang.org/docs/handbook/advanced-types.html#union-types
export type Action = (
  TodoAction
);

Configure the Store

// redux/store.ts

import { Store, applyMiddleware, createStore } from 'redux';
import thunk from 'redux-thunk'; // add-on you may want
import logger from 'redux-logger'; // add-on you may want

import { RootState, rootReducer } from './reducers';

export const store: Store<RootState> = createStore(rootReducer, applyMiddleware(thunk, logger));

Configure Store in Root Component

// components/my-app/my-app.tsx

import { Store } from '@stencil/redux';

import { Action } from '../../redux/actions';
import { RootState } from '../../redux/reducers';
import { store } from '../../redux/store';

@Component({
  tag: 'my-app',
  styleUrl: 'my-app.scss'
})
export class MyApp {
  @Prop({ context: 'store' }) store: Store<RootState, Action>;

  componentWillLoad() {
    this.store.setStore(store);
  }
}

Map state and dispatch to props

:memo: Note: Because the mapped props are technically changed within the component, mutable: true is required for @Prop definitions that utilize the store. See the Stencil docs for info.

// components/my-component/my-component.tsx

import { Store, Unsubscribe } from '@stencil/redux';

import { Action, changeName } from '../../redux/actions';
import { RootState } from '../../redux/reducers';

@Component({
  tag: 'my-component',
  styleUrl: 'my-component.scss'
})
export class MyComponent {
  @Prop({ context: 'store' }) store: Store<RootState, Action>;
  @Prop({ mutable: true }) name: string;

  changeName!: typeof changeName;

  unsubscribe!: Unsubscribe;

  componentWillLoad() {
    this.unsubscribe = this.store.mapStateToProps(this, state => {
      const { user: { name } } = state;
      return { name };
    });

    this.store.mapDispatchToProps(this, { changeName });
  }

  componentDidUnload() {
    this.unsubscribe();
  }

  doNameChange(newName: string) {
    this.changeName(newName);
  }
}

Usage with redux-thunk

Some Redux middleware, such as redux-thunk, alter the store's dispatch() function, resulting in type mismatches with mapped actions in your components.

To properly type mapped actions in your components (properties whose values are set by store.mapDispatchToProps()), you can use the following type:

import { ThunkAction } from 'redux-thunk';

export type Unthunk<T> = T extends (...args: infer A) => ThunkAction<infer R, any, any, any>
  ? (...args: A) => R
  : T;

Example

// redux/user/actions.ts

import { ThunkAction } from 'redux-thunk';

export const changeName = (name: string): ThunkAction<Promise<void>, RootState, void, Action> => async (dispatch, getState) => {
  await fetch(...); // some async operation
};

In the component below, the type of this.changeName is extracted from the action type to be (name: string) => Promise<void>.

// components/my-component/my-component.tsx

import { changeName } from '../../redux/actions';

export class MyComponent {
  changeName!: Unthunk<typeof changeName>;

  componentWillLoad() {
    this.store.mapDispatchToProps(this, { changeName });
  }
}