react-singleton-hook

React Singleton Hook

Manage global state of your React app using hooks.

Installation

To use React Singleton Hook with your React app, install it as a dependency:

# If you use npm:
npm install react-singleton-hook

# Or if you use Yarn:
yarn add react-singleton-hook

This assumes that you’re using npm package manager with a module bundler like Webpack or Browserify to consume CommonJS modules.

Examples

convert any custom hook into singleton hook

In the code below, the user profile is not fetched until useUserProfile used by some component, and once fetched it is never reloaded again, the hook remains mounted forever into hidden component.

import  { useEffect, useState } from 'react';
import { singletonHook } from 'react-singleton-hook';
const api = { async getMe() { return { name: 'test' }; } };

const init = { loading: true };

const useUserProfileImpl = () => {
  const [profile, setProfile] = useState(init);
  useEffect(() => {
    api.getMe()
      .then(profile => setProfile({ profile }))
      .catch(error => setProfile({ error }));
  }, []);

  return profile;
};

export const useUserProfile = singletonHook(init, useSessionImpl);

dark/light mode switch

Whenever Configurator changes darkMode, all subscribed components are updated.

/***************    file:src/services/darkMode.js    ***************/  
import { useState } from 'react';
import { singletonHook } from 'react-singleton-hook';

const initDarkMode = false;
let globalSetMode = () => { throw new Error('you must useDarkMode before setting its state'); };

export const useDarkMode = singletonHook(initDarkMode, () => {
  const [mode, setMode] = useState(initDarkMode);
  globalSetMode = setMode;
  return mode;
});

export const setDarkMode = mode => globalSetMode(mode);


/***************    file:src/compoents/App.js    ***************/

import  React from 'react';
import { useDarkMode, setDarkMode } from 'src/services/darkMode';

const Consumer1 = () => {
  const mode = useDarkMode();
  return <div className={`is-dark-${mode}`}>Consumer1 - {`${mode}`}</div>;
};

const Consumer2 = () => {
  const mode = useDarkMode();
  return <div className={`is-dark-${mode}`}>Consumer2 - {`${mode}`}</div>;
};

const Configurator = () => {
  const mode = useDarkMode();
  return <button onClick={() => setDarkMode(!mode)}>Toggle dark/light</button>;
};

imperatively read hook state for non-react code

import { useState } from 'react';
import { singletonHook } from 'react-singleton-hook';

const initDarkMode = false;
let currentMode = initDarkMode;
let globalSetMode = () => { throw new Error(`you must useDarkMode before setting its state`); };

export const useDarkMode = singletonHook(initDarkMode, () => {
  const [mode, setMode] = useState(initDarkMode);
  globalSetMode = setMode;
  currentMode = mode;
  return mode;
});

export const setDarkMode = mode => globalSetMode(mode);
export const getDarkMode = () => currentMode;

use react-redux (or any other context) inside singletonHook

To use react-redux or any other context-based functionality, singleton hooks should be mounted under provider in your app. To do that, import SingletonHooksContainer from react-singleton-hook and mount anywhere in you app. SingletonHooksContainer must be rendered ealier then any component using singleton hook! By default you are not required to dial with a SingletonHooksContainer, we run this component internally in separate react app.

/***************    file:src/services/currentUser.js    ***************/
import { singletonHook } from 'react-singleton-hook';
import { useSelector } from 'react-redux';

const init = { loading: true };
const useCurrentUserImpl = () => {
  const session = useSelector(state => state.session);
  if (session.loading) return init;
  return session.user;
};

export const useCurrentUser = singletonHook(init, useCurrentUserImpl);

/***************    file:src/App.js    ***************/

import React from 'react';
import ReactDOM from 'react-dom';
import { SingletonHooksContainer } from 'react-singleton-hook';
import { Provider } from 'react-redux';
import store from 'src/store';
import App from 'src/views';

const app = (
  <Provider store={store}>
    <>
      <SingletonHooksContainer/>
      <App/>
    </>
  </Provider>
);

ReactDOM.render(app, document.getElementById('root'));

top-level components updated before low-level components

/***************    file:src/services/session.js    ***************/

import { useEffect, useState } from 'react';
import { singletonHook } from 'react-singleton-hook';

const initState = { loading: true };
let setSessionGlobal = () => { throw new Error('you must useSession before login'); };

const useSessionImpl = () => {
  const [session, setSession] = useState(initState);
  setSessionGlobal = setSession;
  useEffect(() => { setSession({ loggedIn: false }); }, []);
  return session;
};

export const useSession = singletonHook(initState, useSessionImpl);

export const login = (name, pass) => {
  setSessionGlobal({ loggedIn: true, user: { name: 'test' } });
};

/***************    file:src/index.js    ***************/
import React, { useEffect } from 'react';
import ReactDOM from 'react-dom';
import { login, useSession } from 'src/services/session';

const LoggedInView = () => {
  const session = useSession();
  console.log(`LoggerInView rendered with ${JSON.stringify(session)}`);
  return null;
};

const LoggedOutView = () => {
  const session = useSession();
  console.log(`LoggedOutView rendered with ${JSON.stringify(session)}`);
  return null;
};

const WaitingForSessionView = () => {
  const session = useSession();
  console.log(`WaitingForSessionView rendered with ${JSON.stringify(session)}`);
  return null;
};

const MainComponent = () => {
  const session = useSession();

  useEffect(() => {
    setTimeout(() => { login('testuser'); }, 2000);
  }, []);

  console.log(`MainComponent rendered with ${JSON.stringify(session)}`);

  if (session.loading) return <WaitingForSessionView/>;
  if (session.loggedIn) return <LoggedInView/>;
  return <LoggedOutView/>;
};


ReactDOM.render(<MainComponent/>, document.getElementById('root'));

/***************    console.log    ***************/
/*

MainComponent rendered with {"loading":true}
WaitingForSessionView rendered with {"loading":true}
MainComponent rendered with {"loggedIn":false}
LoggedOutView rendered with {"loggedIn":false}
MainComponent rendered with {"loggedIn":true,"user":{"name":"test"}}
LoggerInView rendered with {"loggedIn":true,"user":{"name":"test"}}

*/

React Native

To use this library with react-native you always have to mount SingletonHooksContainer manually. See how to do it in example: use react-redux (or any other context) inside singletonHook

Server Side Rendering

Singleton hooks are ignored during SSR and always return initial value.