Real-time app using React, Redux, Tailwind CSS & Firebase - Part 3

October 24, 2021

#javascript

9

#react

4

#redux

3

Table of contents

• Setting up

• Creating Heading component

• Creating UserName component

  • Crafting the state
    • Constants
    • Actions
    • Reducers

• Adding Firebase persistence

  • Push updates to Firebase

  • Receive updates from Firebase

    ---

NOTE: This series goes a bit unconventional, by not using any libraries or abstractions for Redux, following plain Flux architecture conventions. The recommended way of writing Redux is by using RTK (Redux Toolkit).

Previously in part 2, we did all the hard work of setting up Redux & Firebase, plus creating and connecting our first component. In this part, we are going to add the initial user functionality by assigning a default, random username when first visiting the app and also being able to edit it.

As per the requirements laid out in the first part:

• Each client gets assigned a default random username when first visiting the app which he can also refresh.
• Any participant can edit his/her username, as well as the feature-to-be-implemented title.

So, let's go and see what we can do! 🚀🚀

Setting up

The Heading component is going to host the application title, as well as the UserName component itself. Inside the components folder create a Heading folder and add two more things:

• A UserName folder, which is going to hold the relevant component.
• A Heading.js file.

A visual reminder of what we are building:

We are also going to create three utility functions to make local storage manipulation easier throughout the app. Inside the utils folder create three files named getLocalStorage.js, setLocalStorage.js and removeLocalStorage.js and paste the following functions, to each one respectively:

// getLocalStorage.js

const getLocalStorage = key => {
    return JSON.parse(localStorage.getItem(key));
};

export default getLocalStorage;

// setLocalStorage

const setLocalStorage = ({ key, value }) => {
    localStorage.setItem(key, JSON.stringify(value));
};

export default setLocalStorage;

// removeLocalStorage

const removeLocalStorage = key => {
    localStorage.removeItem(key);
};

export default removeLocalStorage;

Creating Heading component

Import our UserName component (which we are going to implement right after) and place it inside the Heading, along with a simple title for our app and some styles. Paste the following code inside the Heading.js file:

import UserName from "./UserName";

const Heading = () => {
    return (
        <div className="md:flex md:items-center md:justify-between">
            <div className="flex-1 min-w-0">
                <h2 className="text-2xl font-bold leading-7 text-gray-900 sm:text-3xl">
                    Scrum Voting App
                </h2>
            </div>
            <div className="mt-10 flex md:mt-0 md:ml-4 justify-center">
                <div>
                    <UserName />
                </div>
            </div>
        </div>
    );
};

export default Heading;

Creating UserName component

Under components/Heading/UserName create an index.js file and add the following code:

// Generic Input component we also used for FeatureTitle
import Input from "../../Input/Input"; 

import { useDispatch, useSelector } from "react-redux";
import { useEffect } from "react";

// Redux action/thunks
import updateUser from "../../../store/actions/users/updateUser";

// Simple utility to retrieve and parse values from local storage
import getLocalStorage from "../../../utils/getLocalStorage";
import createDefaultUser from "../../../common/createDefaultUser";

const UserName = () => {
    const dispatch = useDispatch();
    const state = useSelector(state => state.users);

    const currentUserId = getLocalStorage("userId");
  
  // Default user creation handling
    useEffect(() => {
        // Create a user if none exists
        if (currentUserId === null) createDefaultUser(dispatch);
    }, [dispatch, currentUserId]);

    // Retrieve current user using saved id from local storage
    const user = state.users.find(user => Object.keys(user)[0] === currentUserId);

    const handleUserUpdate = event => {
        // Action payload (updated user object)
        const updatedUser = {
            id: currentUserId,
            data: {
                ...user[currentUserId],
                username: event.target.value
            }
        };

        dispatch(updateUser(updatedUser));
    };

    return (
        <Input
            label="Username"
            placeholder="Type a username..."
            handleChange={event => handleUserUpdate(event)}
            // While loading display a loading message, else display current user
            value={user ? user[currentUserId].username : "Loading username..."}
            name="username"
            className="inline-flex items-center px-4 py-2 border border-transparent rounded-md shadow-sm text-sm font-medium focus:outline-none focus:ring-2 focus:ring-offset-2 focus:ring-indigo-500"
            // Disable editing while loading
            disabled={user ? false : true}
        />
    );
};

export default UserName;

I have placed some comments to make things easier to grasp. We basically add an Input component, which will a have a dual role: Displaying our current username and changing it.

Crafting the state

Let's go ahead and create anything state-related to add and update users.

Constants

Under store/constants create a file named users.js. It will contain all the action constants for the user slice.

For now, we only want ADD, UPDATE and REVERT functionality, so go ahead and add those three constants:

export const ADD_USER = "ADD_USER";
export const UPDATE_USER = "UPDATE_USER";
export const SET_USERS = "SET_USERS"; // This is going to be used for state reversion

Actions

Under store/actions create a folder named users. It will hold all user-related actions. First, we are going to create an action to add a user, so go ahead and create a file named addUser.js. Then paste the following code:

// Firebase module to add user
import firebaseAddUser from "../../../firebase/users/addUser";
import setLocalStorage from "../../../utils/setLocalStorage";

const addUser = payload => (dispatch, getState, getFirebase) => {
    // Get firebase object
    const firebase = getFirebase();
    const state = getState();

    // Username of the new user
    const { username: value } = payload;

    // Get old state (used to revert in case of error)
    const {
        users: { users: oldState }
    } = state;

    // Pass necessary data to our firebase module
    const config = {
        ref: "users/", // Firebase reference to perform query on
        payload,
        oldState,
        firebase,
        dispatch
    };

    // Update local storage with the username to create persistency
    setLocalStorage({ key: "username", value });

    // Add user to firebase
    firebaseAddUser(config);
};

export default addUser;

What we just created above is called a thunk which, as we stated here in the previous part, is basically an enhanced action which returns a function instead of an object. Inside this function we can run any asynchronous code we want, as well as dispatch other actions. Notice how dispatch, getState and getFirebase methods are provided as arguments to our action, by the thunk middleware.

Once again, I hope that the comments help explain what's going on above. We are doing two main things here:

• Creating a config object to pass to firebaseAddUser (which is called asynchronously).
• Persist username to local storage. This is going to be useful in getting the user identified correctly and not creating a new one, each time he visits the app on the same browser (provided he doesn't clear the local storage).

Also, notice how we are not dispatching any action to update the state. The reason is that there can be no change in the UI state (and thus a visual change), until we get a response from the database. It's also an automatic and one-time procedure, while the result is stored in local storage, so no Redux persistence is needed.

Similarly, let's create the action to update a user. Again, under the actions directory create a file named updateUser.js and paste the following code:

import { UPDATE_USER } from "../../constants/users";

// Firebase module to update user
import firebaseUpdateUser from "../../../firebase/users/updateUser";

const updateUser = ({ id, data }) => (dispatch, getState, getFirebase) => {
    const firebase = getFirebase();
    const state = getState();

    // Grab user object form state (used to revert in case of error)
    const [oldState] = state.users.users.filter(user => user[id]);

    const config = {
        ref: `users/${id}`, // Firebase reference to perform query on
        payload: data,
        oldState,
        firebase,
        dispatch,
        resetActionType: UPDATE_USER
    };

    // Update user record in firebase
    firebaseUpdateUser(config);

    // Dispatch asynchronously to maintain a responsive UI
    dispatch({
        type: UPDATE_USER,
        payload: {
            [id]: data
        }
    });
};

export default updateUser;

Some notes:

• Regarding the ref property usage you can check the Firebase Documentation. Basically, it's a "path" used to specify the location in our database, upon which the query is going to execute.
• Regarding the two custom firebase modules, firebaseAddUser and firebaseUpdateUser, we are going to create them right after finishing with the reducers below.
• The reason why we are specifying the resetActionType is because later on, we are going to be using a different reducer when resetting the state, based on whether we are updating a single user or resetting the votes for every user.
• In contrast to the addUser action, here we are dispatching an action to update the state which happens asynchronously and independently of the Firebase update, in order to maintain a responsive UI.

Reducers

Under store/reducers create a users.js file to create our users reducers. Then paste the following:

import * as actionTypes from "../constants/users";

const initState = {
    users: []
};

const usersReducer = (state = initState, action) => {
    switch (action.type) {
        case actionTypes.ADD_USER: {
            return {
                ...state,
                users: [...state.users, action.payload]
            };
        }

        case actionTypes.UPDATE_USER: {
            return {
                ...state,
                users: state.users.map(user => {
                    /*
                     * Grab IDs
                     */
                    const [stateUserId] = Object.keys(user);
                    const [payloadUserId] = Object.keys(action.payload);

                    // Return the same user object if IDs don't match
                    if (stateUserId !== payloadUserId) return user;

                    // Else replace objet and update user
                    return action.payload;
                })
            };
        }

        case actionTypes.SET_USERS:
            return {
                ...state,
                users: action.payload // Replace the whole users array
            };

        default:
            return state;
    }
};

export default usersReducer;

Don't forget to also combine the new reducer with the root one. Make sure that store/reducers/index.js looks like this:

import { combineReducers } from "redux";
import feature from "./feature";
import users from "./users"; // <-- New line

export default combineReducers({
    feature,
    users // <-- New line
});

Adding Firebase persistence

Push updates to Firebase

Now we have to persist our Redux data to Firebase, just as we did in the previous part for the FeatureTitle component. Under src/firebase create a users folder and add an addUser.js file. Then paste the following code:

import { SET_USERS } from "../../store/constants/users";

const addUser = ({ ref, payload, oldState, firebase, dispatch }) => {
    firebase
        .ref(ref) // Select ref to update
        .push(payload) // Push the new user
  
        // Handle error
        .catch(e => {
            // Revert to old state in case of error
            dispatch({
                type: SET_USERS,
                payload: oldState
            });
           
            /* 
            * Dispatch snackbar with our browser's
            * built-in, sophisticated notification system 😎
            */
            alert("There was an error performing the request.");
        });
};

export default addUser;

The above code will handle the persistence of any new user that gets added to the database. To persist any updates made, add the following action in a file named updateUser.js:

import debounce from "../../utils/debounce";

const updateUser = ({
    ref,
    payload,
    oldState,
    firebase,
    dispatch,
    resetActionType
}) => {
    firebase
        .ref(ref)
        .set(payload)
        .then(error => {
            // Revert to old state in case of error
            if (error) {
                dispatch({
                    type: resetActionType,
                    payload: oldState
                });

                /*
                 * Dispatch snackbar with our browser's
                 * built-in, sophisticated notification system 😎
                 */
                alert("There was an error performing the request.");
            }
        });
};

export default debounce(updateUser, 500);

The logic is very similar here, except that we are also debouncing the action, since it is subject to manual user typing and can very well be spammed.

Receive updates from Firebase

Same as with the FeatureTitle component from the previous part, we need to setup the appropriate listeners in order to successfully receive updates from Firebase and update our Redux store. Inside store/actions/users folder the we have created, add a new file named setupFirebaseListeners.js. The code inside this file is going to do exactly that: Setup the appropriate listeners in order to subscribe to updates from Firebase.

import { ADD_USER, UPDATE_USER } from "../../constants/users";

import getLocalStorage from "../../../utils/getLocalStorage";
import setLocalStorage from "../../../utils/setLocalStorage";

const setupUsersListener = () => (dispatch, getState, getFirebase) => {
    const firebase = getFirebase();
    const usersRef = firebase.database().ref("users");

    /* User updates handling */
    usersRef.on("child_changed", snapshot => {
        const { key } = snapshot;

        // Update state
        dispatch({
            type: UPDATE_USER,
            payload: {
                [key]: snapshot.val()
            }
        });
    });

    /* Users loading and new user handling */
    usersRef.on("child_added", snapshot => {
        const user = snapshot.val(); // get user object
        const { username } = user;
        const { key } = snapshot; // user ID

        if (username === getLocalStorage("username")) {
            // Save user id in local storage if it matches own username
            setLocalStorage({ key: "userId", value: key });
        }

        // Update state
        dispatch({
            type: ADD_USER,
            payload: {
                [key]: user
            }
        });
    });
};

export default setupUsersListener;

The thunk we created above is going to be dispatched once on application start and listeners for the relevant Firebase events are going to be registered. Import the action and dispatch it inside App.js:

import "./App.css";

import FeatureTitle from "../components/FeatureTitle";

import { useDispatch } from "react-redux";
import { useEffect } from "react";

import setupFeatureListeners from "../store/actions/feature/setupFirebaseListeners";
import setupUsersListeners from "../store/actions/users/setupFirebaseListeners"; // <--- New line

function App() {
    const dispatch = useDispatch();

    // Setting up listeners
    useEffect(() => {
        dispatch(setupUsersListeners()); // <--- New line
        dispatch(setupFeatureListeners());
    }, [dispatch]);

    return (
        <main className="max-w-7xl mx-auto my-5 px-4 sm:px-6 lg:px-8">
            <div className="flex flex-col flex-wrap max-w-3xl mx-auto mt-10">
                <div className="flex justify-center">
                    <FeatureTitle />
                </div>
            </div>
        </main>
    );
}

export default App;

That's it! Run npm start, visit localhost:3000 (or whatever port you are using) and you should be able to see a default username assigned on the top right corner. Try editing it on both your browser and firebase and make sure that the two are synced. If you try to open the app in Incognito mode, you are going to get assigned a new user, because of a clean local storage.

Thanks for reading, stay tuned for the next one 🎉🎉