Redux Shopping Cart Refactor to The Context API and React Hooks

Redux Shopping Cart Refactor to The Context API and React Hooks

In the following documentation, we are going to, from the ground up, refactor a Redux shopping cart product’s data into the Context Provider pattern.

In the following documentation, we are going to, from the ground up, refactor a Redux shopping cart product’s data into the Context Provider pattern.

This guide’s primary focus will be on comparing and contrasting Redux vs. the Context API.

The refactor aims to provide a guided example, as well as deepen our understanding of state management in React, implementing various efficient scalable patterns.

Process Overview

The shopping cart application will be pulled from the official Redux GitHub repository to maintain a standard example environment.

We will trace the Flux-like pattern of Redux in the shopping cart app, and by focusing on the product data, implement a successful state management refactor by leveraging React Hooks and the Context API.

Guide Outline
  • Clone Redux.
  • Scalable state management analysis.
  • Tracing shopping cart product data.
  • Reducers and Actions.
  • Thunk and logger: middleware vs. dispatch.
  • Implement Context Provider pattern.
  • HOCs, HOFs, and Redux Connect().
  • Leveraging React Hooks and useContext.
  • setTimeout() vs. promises.
  • Final Context Provider pattern refactor.

Alright. So, let’s grab some coffee and get this show on the road.

Please note that a basic level requirement of Node and React is beneficial for getting started and for general concept comprehension.

Clone Redux

First off, go to the Redux GitHub repository.

Clone the source project by copying the SSH link and running git clonein the command prompt.

git clone [email protected]:reduxjs/redux.git

Copy the Shopping Cart folder which can be found in the folder directory: examples/shopping-cart and paste it somewhere where you can conveniently access it throughout this guide.

Now, using the terminal (Mac) command prompt, go cd shopping-cart into the shopping-cart folder directory and install all required node modules simply by running npm install.

Open the code source into your text editor and then launch the local development server by running npm start. We should now see the shopping cart application up and running in the browser.

Open up the DevTools Console (Chrome) to verify this and also note Redux Logger is activated and working.

Excellent. Now, let’s take a quick yet savory sip of coffee before proceeding.

Application Structure and API Emulation

Simply by viewing the shopping cart’s display in the browser, we can ascertain two main sections: the products section and the cart section.

  • The products section contains a list of products available to purchase including the title, price, and quantity. As well, there is an add to cart button to individually select products for the cart.
  • When we click on the iPad 4 Mini add to cart button, we see that the cart sectiongets updated, including the total price. If we scroll down to the Logger in the DevTools and check on the previous state vs. the next state, the products inventory is updated and reflected accordingly.


Next State Logger

But where are we receiving our product’s item data to begin with?

Good question. In the Redux shopping cart project’s API folder, we see a products.json file with a list of items and a shop.jsfile, grabbing and exporting the array from products.json.

The shop.js getProducts object’s property has an additional setTimeout function set to 100 milliseconds to simulate an Async-esque operation of fetching the shopping cart items from a real-world API scenario.

const TIMEOUT = 100
export default { getProducts: (cb, timeout) => setTimeout(() => cb(_products), timeout || TIMEOUT),
buyProducts: (payload, cb, timeout) => setTimeout(() => cb(), timeout || TIMEOUT)}

If we change the TIMEOUT const numerical value to 2000 (two seconds) and go back to the browser and refresh, we’ll notice the initial products render will now take two full seconds before displaying: const TIMEOUT = 2000.

Having now located and assessed our API data structure and retrieval setup, let’s fully trace the state retrieval management process of the products data in Redux.

Products: Actions, Reducers, and Thunk Middleware

If we go into the actions folder, the index.jscontains the following code:

import shop from '../api/shop'
import * as types from '../constants/ActionTypes'
const receiveProducts = products => ({
type: types.RECEIVE_PRODUCTS,
products})
export const getAllProducts = () => dispatch => {
shop.getProducts(products => {
dispatch(receiveProducts(products))
})}

The receiveProducts establishes the type types.RECEIVE_PRODUCTS and a payload of products.

This type is set up as const in the ActionTypes file. It’s then passed to a switch statement in two reducers, visibleIds and byIds, located in the reducer folder in products.js.

Maintaining focus on the actions, also notice a getAllProducts function which returns a dispatch function that grabs the products.json from the shop and sends the data payload of products into our receiveProducts action.

Back in the main index.jsfile located in our src folder, if we remove our Thunk middleware: const middleware = [ ];, we receive the following error:

Since the action performs an emulated real-life API fetch, set to a setTimeout(), we need to implement Thunk to correctly process and handle the async action.

Have a contemplative sip or two of coffee and return Thunk back to the middleware: const middleware = [thunk].

We’ve now managed to complete a full assessment of the product’s data API display: How and where we’re receiving the data and managing it in our application.

With this assessment, let’s proceed by setting up the architecture for the Context Provider pattern.

Context Provider Pattern Setup

Back in the project’s src folder, create a new folder called providers and file inside of the folder named products.provider.js.

In the products provider file, we’re going to set up a products provider pre-test demonstration with the following code:

products.provider.js

import React,{createContext, useState} from 'react'

export const ProductsContext = createContext({
    test: ''
})

const ProductsProvider = ({children}) => {
    const [test] = useState('the products provider has been successfully connected :)')
    return (
        <ProductsContext.Provider value={{test}}>
            {children}
        </ProductsContext.Provider>
    )
}

export default ProductsProvider

The code above first brings in createContext to access the React Context API and the useState Hook. Then, we set our context to the constProductsContext where we initialize an object that takes the property of test which we set to an empty string.

After that, we create the ProductsProviderfunction which takes the object of children props as its parameter, passing the props of children through the Context.Provider.

Within, we initialize the state of test to a string: const [test] = useState(‘the products provider has been successfully connected :)’).

ProductsProvider then explicitly returns the ProductsContext to the Provider with a value of the object test passing in the state with the property of children.

Alright, let’s stop for a second. Might sound like a bit of mouthful, but it’s actually quite simple, except that it takes a bit of following in terms of how things are hooked up.

If you’re having trouble following, go back and take each step one at a time, slowly. Just make sure you follow the traces and it will make much more sense, otherwise, if you’ve managed to follow along up to this part, kudos and let’s keep moving!

The products Context is made aware of an empty string of test in which we initialize state by setting up a const test in the product’s Provider, also taking a string.

We can then set the state of test to the object property of test by setting the ProductsContext.Provider value={{test}} to an object receiving test.

Finally, pass the children over as a wrapper.

To enable the Provider to be wrapped around the component/container of our choosing, let’s simply go into the index.js filein thesrc folder, import the Provider, and wrap it around our application granting it access to the children.

index.js

import React from 'react'
import { render } from 'react-dom'
import { createStore, applyMiddleware } from 'redux'
import { Provider } from 'react-redux'
import { createLogger } from 'redux-logger'
import thunk from 'redux-thunk'
import reducer from './reducers'
import { getAllProducts } from './actions'
import App from './containers/App'
import ProductsProvider from './provider/products.provider'

const middleware = [thunk];
if (process.env.NODE_ENV !== 'production') {
  middleware.push(createLogger());
}

const store = createStore(
  reducer,
  applyMiddleware(...middleware)
)

store.dispatch(getAllProducts())

render(
  <ProductsProvider>
  <Provider store={store}>
    <App />
  </Provider>
  </ProductsProvider>,
  document.getElementById('root')
)

Note that the ProductsProvider wraps over the Redux store Provider illustrating it at the utmost top of our application’s state management tree.

Context Provider Pattern Test

Time to drink some more coffee and test if our new Context Provider is effectively working.

Go into the containers folder in productsContainer.js.We can now bring in the useContext Hook and destructure our test from the ProductsContext into our products container to see if it works.

productsContainer.js

import React,{useContext} from 'react'
import PropTypes from 'prop-types'
import { connect } from 'react-redux'
import { addToCart } from '../actions'
import { getVisibleProducts } from '../reducers/products'
import ProductItem from '../components/ProductItem'
import ProductsList from '../components/ProductsList'
import {ProductsContext} from '../provider/products.provider'

const ProductsContainer = ({ products, addToCart }) => {
  const {test} = useContext(ProductsContext)
  console.log(test)
return (
  <ProductsList title="Products">
    {products.map(product =>
      <ProductItem
        key={product.id}
        product={product}
        onAddToCartClicked={() => addToCart(product.id)} />
    )}
  </ProductsList>
)
    }
ProductsContainer.propTypes = {
  products: PropTypes.arrayOf(PropTypes.shape({
    id: PropTypes.number.isRequired,
    title: PropTypes.string.isRequired,
    price: PropTypes.number.isRequired,
    inventory: PropTypes.number.isRequired
  })).isRequired,
  addToCart: PropTypes.func.isRequired
}

const mapStateToProps = state => ({
  products: getVisibleProducts(state.products)
})

export default connect(
  mapStateToProps,
  { addToCart }
)(ProductsContainer)

Our productsContainer.jsshould now be updated to the code above. Upon browser refresh, DevTools now displays the test log successfully.

Very nice. Our Context Provider pattern for our product’s display is now fully connected and ready for implementation.

Let’s head back to our products.provider.js file and completely refactor the product’s data into our Context API setup.

Migrate Products Data to Context Provider

We’ll now update the products.provider.jscode. First, we’ll import the shop from our shop.js.

We’ll establish a new property in our context object for the products’ data and set it to an empty array. We’ll then import the useEffect Hook as well from React and create a products’ state also set to an empty array.

Then, we’ll leverage the useEffect Hook to render our product’s data by setting the hook to async to await grabbing the product’s data from our shop and setting the response to our products state.

We’ll leave an empty array in our useEffect so that the mounting life-cycle executes once, by default.

Finally, we’ll bring the product’s state into the Context Provider’s value object.

products.provider.js

import React,{createContext, useState, useEffect} from 'react'
import shop from '../api/shop'

export const ProductsContext = createContext({
    test: '',
    products: []
})

const ProductsProvider = ({children}) => {
    const [test] = useState('the products provider has been successfully connected :)')
    const [products, setProducts] = useState([])
    useEffect(async ()=> {
        const response = await shop.getProducts(products => products)
        setProducts(response)
},[])
    return (
        <ProductsContext.Provider value={{test, products}}>
            {children}
        </ProductsContext.Provider>
    )
}

export default ProductsProvider
Final Implementation and Async vs. Promises

Saving the newly updated code, let’s refill our coffee cups and head back to the productsContainer.js file.

Let’s update our products’ data to be called from our Products Provider instead of our Redux Provider by destructuring products off the ProductsContext and removing products destructured props from the ProductsContainer, as shown below.

productsContainer.js

After saving everything, we will now run into the following error.

No need to panic, this is expected behavior. Since setTimeout does not return a promise, async await will not execute accordingly to prevent JavaScript from running until the setTimeout interval value is completed.

To maintain the coded simulation effect of this API, let’s go back to the shop.jsfile and promisify the code.

Let’s create an async anonymous function and wrap a new Promise around the getProduct data retrieval property.

* Mocking client-server processing */
import _products from './products.json'
const TIMEOUT = 100
export default {
getProducts: async ()=> new Promise((cb, timeout) => setTimeout(() => cb(_products), timeout || TIMEOUT)),
buyProducts: (payload, cb, timeout) => setTimeout(() => cb(), timeout || TIMEOUT)
}

With the new promise patch modification, getProducts will now return a promise for our async useEffect to retrieve.

Saving this latest update, our product’s shopping cart data will once again successfully be displayed upon mounting.

Congratulations. We have now migrated our initial product’s data display from Redux into the newly instated Context Provider pattern.

Take a congratulatory sip or three of coffee and let’s do some final code clean-up and review.

Final Refactor and Conclusion

Back in our productsContainer.js file, we can delete our mapStateToProps const and remove it from our connect since our products’ data retrieval is no longer being managed by Redux.

export default connect(null,{ addToCart })(ProductsContainer)

Our application will continue to work as is it did before, demonstrating a successful refactor.

Just like Connect() is a higher-order component that wrapped around our productsContainer component to pass over the data state to props, our ProductsProvider now acts in its place.

The Products Context passes the children props of the products data state as the Products Provider wraps around the main application in our index.jsby being placed at the top of the app tree.

Although both implementations are effective, this guide in no way favors one over the other as an ultimate go-to.

It simply depends on each application and these are the decisions we need to think about carefully and make to achieve the most effective state management path for our applications.

This guide has purely been intended to simulate a refactor process and analysis of working with Context and Redux as a basic starting point.

Thank you for checking this out and I hope you found some of this helpful!

How to Implement Redux in 24 Lines of JavaScript?

How to Implement Redux in 24 Lines of JavaScript?

Redux is among the most important JavaScript libraries ever created. In this posr, you'll learn how to Implement Redux in 24 lines of JavaScript. Inspired by prior art like [Flux](https://facebook.github.io/flux/) and...

Redux is among the most important JavaScript libraries ever created. In this posr, you'll learn how to Implement Redux in 24 lines of JavaScript.

Inspired by prior art like Flux and Elm, Redux put JavaScript functional programming on the map by introducing a scalable architecture of three simple points.

If you're new to Redux, consider reading the official docs first.

Redux Is Mostly Convention

Consider this simple counter application that uses the Redux architecture. If you'd like to jump ahead check out the Github repo for it.

State lives in a single tree

The application's state looks like this.

const initialState = { count: 0 };

Actions declare state changes

By Redux convention, I do not directly modify (mutate) the state.

// DON'T do this in a Redux app
state.count = 1;

Instead I create all the actions the user may leverage in the application.

const actions = {
  increment: { type: 'INCREMENT' },
  decrement: { type: 'DECREMENT' }
};

Reducer interprets action and updates state

The last architectural piece calls for a reducer, a pure function that returns a new copy of your state based on the previous state and action.

  • If increment is fired, increment state.count.
  • If decrement is fired, decrement state.count.
const countReducer = (state = initialState, action) => {
  switch (action.type) {
    case actions.increment.type:
      return {
        count: state.count + 1
      };

    case actions.decrement.type:
      return {
        count: state.count - 1
      };

    default:
      return state;
  }
};

No Redux so far

Did you notice that we haven't touched the Redux library yet? We've just created some objects and a function. This is what I mean by "mostly convention", 90% of Redux doesn't require Redux!

Let's implement Redux

To put this architecture to use, we must plug it into a store. We'll implement just one function–createStore.

It's used like this.

import { createStore } from 'redux'

const store = createStore(countReducer);

store.subscribe(() => {
  console.log(store.getState());
});

store.dispatch(actions.increment);
// logs { count: 1 }

store.dispatch(actions.increment);
// logs { count: 2 }

store.dispatch(actions.decrement);
// logs { count: 1 }

And here's our initial boilerplate. We'll need a list of listeners and the initial state supplied by the reducer.

const createStore = (yourReducer) => {
    const listeners = [];
    let currentState = yourReducer(undefined, {});
}

Whenever someone subscribes to our store, they get added to the listeners array. The is important because every time someone dispatches an action, all the listeners must be notified in a loop.

Calling yourReducer with undefined and an empty object returns the initialState we installed up above. This gives us a proper value to return when we call store.getState(). Speaking of which, let's create that method.

store.getState()

This is a function that returns the latest state from the store. We'll need this to update our UI every time the user clicks a button.

const createStore = (yourReducer) => {
    const listeners = [];
    let currentState = yourReducer(undefined, {});

    return {
        getState: () => currentState
    };
}

store.dispatch(action)

This is a function that takes an action as a parameter. It feeds that action and the currentState to yourReducer to get a new state. Then dispatch notifies everyone subscribed to the store.

const createStore = (yourReducer) => {
  const listeners = [];
  let currentState = yourReducer(undefined, {});

  return {
    getState: () => currentState,
    dispatch: (action) => {
      currentState = reducer(currentState, action);

      listeners.forEach((listener) => {
        listener();
      });
    }
  };
};

store.subscribe(listener)

This is a function that lets you be notified when the store receives an action It's good to use store.getState() in here to get your latest state and update your UI.

const createStore = (yourReducer) => {
  const listeners = [];
  let currentState = yourReducer(undefined, {});

  return {
    getState: () => currentState,
    dispatch: (action) => {
      currentState = reducer(currentState, action);

      listeners.forEach((listener) => {
        listener();
      });
    },
    subscribe: (newListener) => {
      listeners.push(newListener);

      const unsubscribe = () => {
        listeners = listeners.filter((l) => l === newListener);
      };

      return unsubscribe;
    }
  };
};

subscribe returns a function called unsubscribe that you can call when you're no longer interested in listening to the store's updates.

All Together Now

Let's hook this up to our buttons and view the final source code.

// simplified createStore function
const createStore = (reducer) => {
  const listeners = [];
  let currentState = reducer(undefined, {});

  return {
    getState: () => currentState,
    dispatch: (action) => {
      currentState = reducer(currentState, action);

      listeners.forEach((listener) => {
        listener();
      });
    },
    subscribe: (newListener) => {
      listeners.push(newListener);

      const unsubscribe = () => {
        listeners = listeners.filter((l) => l === newListener);
      };

      return unsubscribe;
    }
  };
};

// Redux architecture pieces
const initialState = { count: 0 };

const actions = {
  increment: { type: 'INCREMENT' },
  decrement: { type: 'DECREMENT' }
};

const countReducer = (state = initialState, action) => {
  switch (action.type) {
    case actions.increment.type:
      return {
        count: state.count + 1
      };

    case actions.decrement.type:
      return {
        count: state.count - 1
      };

    default:
      return state;
  }
};

const store = createStore(countReducer);

// DOM elements
const incrementButton = document.querySelector('.increment');
const decrementButton = document.querySelector('.decrement');

// Wire click events to actions
incrementButton.addEventListener('click', () => {
  store.dispatch(actions.increment);
});

decrementButton.addEventListener('click', () => {
  store.dispatch(actions.decrement);
});

// Initialize UI display
const counterDisplay = document.querySelector('h1');
counterDisplay.innerHTML = parseInt(initialState.count);

// Update UI when an action fires
store.subscribe(() => {
  const state = store.getState();

  counterDisplay.innerHTML = parseInt(state.count);
});

And once again here's our final UI.

If you're interested in the HTML/CSS I used, here's the GitHub repo again!

Thanks for reading

Dumb decorators for redux & redux-observable & react-redux

Dumb decorators for redux & redux-observable & react-redux

redux-epics-decorator Dumb decorators for redux & redux-observable & react-redux & redux-actions.

redux-epics-decorator

A Dumb wrapper for redux redux-observable react-redux redux-actions injection-js

Features
  • 🚀 Less boilerplate codes
  • 🦄 No magic string Action Types
  • 💚 Type Safe, typecheck in Payload
  • ⛏ Go to definition, go to your Reducer/Epics with one click
  • 🖇 Easy to intergrate into existed redux-observable or other redux middlewares

but which more important is:

Dependeicies
  • yarn add redux redux-observable rxjs redux-actions react-redux
  • yarn add redux-epics-decorator
Full example project

fixtures

Use yarn && yarn start to play with it.

Usage
// module.ts
import { Action } from 'redux-actions'
import { ActionsObservable } from 'redux-observable'
import { Observable } from 'rxjs'
import { exhaustMap, takeUntil } from 'rxjs/operators'

import { generateMsg, Msg } from '../service'
import { EffectModule, Module, Effect, Reducer, ModuleActionProps, DefineAction } from 'redux-epics-decorator'

export interface StateProps {
  currentMsgId: string | null
  allMsgs: Msg[]
}

@Module('your_module_name')
export class Module1 extends EffectModule<StateProps> {
  readonly defaltState: StateProps = {
    currentMsgId: null,
    allMsgs: []
  }

  @DefineAction('dispose') dispose: Observable<void>

  @Effect({
    success: (state: StateProps, { payload }: Action<Msg>) => {
      const { allMsgs } = state
      return { ...state, allMsgs: allMsgs.concat([payload!]) }
    }
  })
  getMsg(action$: Observable<void>) {
    return action$.pipe(
      exhaustMap(() => generateMsg().pipe(
        takeUntil(this.dispose),
        map(this.createAction('success')), // up in Effect Decorator
        // dispatch a normal Redux Action
        // intergrate to your existed redux system
        endWith(this.markAsGlobal({
          type: 'notification',
          payload: {
            type: 'success',
            msg: '✨ Get message success!'
          }
        })),
      ))
    )
  }

  @Reducer('select_msg')
  selectMsg(state: StateProps, { payload }: Action<string>) {
    return { ...state, currentMsgId: payload }
  }
}

export type DispatchProps = ModuleActionProps<Module1>
// container.tsx
import { Module1, StateProps, DispatchProps } from './module'

interface OtherProps {
  price: number
  count: number
}
type Props = StateProps & OtherProps & DispatchProps

const mapStateToProps = (state: GlobalState): StateProps => ({
  ...state.yourcomponent,
  price: otherModule.price,
  count: otherModule.count,
})

class YourComponent extends React.PureComponent<Props> {
  // your codes ...

  render() {
    // this is same to this.props.dispatch({ type: 'Module1/getMsg' })
    this.props.getMsg() // () => Action<void>, type safe here
    return (
      <div />
    )
  }
}

export connect(Module1)(mapStateToProps)(YourComponent)
// store
import { combineModuleEpics, combineModuleReducers, createEpicMiddleware } from 'redux-epics-decorator'

import { StateProps as YourComponentStateProps, Module1 } from './yourcomponent/module'

interface GlobalState {
  yourcomponent: YourComponentStateProps
}

const rootEpic = combineEpics(
  combineModuleEpics(
    Module1,
    Module2,
    Module3,
  ),
  // other normal epics from redux-observable
  epic1,
  epic2,
  epic3,
)

const rootReducer = combineReducers({
  ...combineModuleReducers({
    module1: Module1,
    module2: Module2,
    module3: Module3,
  }),
  // other normal reducers from redux-actions
  other1: otherReducers1,
  other2: otherReducers2,
})

const epicMiddleware = createEpicMiddleware()

export default store = createStore<GlobalState>(rootReducer, compose<any>(
  applyMiddleware(
    epicMiddleware
  )
))

epicMiddleware.run(rootEpic)
Download Details:

Author: Brooooooklyn

Official Website: https://github.com/Brooooooklyn/redux-epics-decorator

Redux Basics

Redux Basics

In this post, the simplest React Redux tutorial I wish I had when I started learning. ... Having seen the basics let's now talk about what problem Redux tries to solve.

Throughout last week, I had my first taste of Redux. During this time, we implemented Redux with React but, it does not need to be used exclusively with React. However, this has been my only experience with it thus far, so I will explain it the way it is used with React.

Upon introduction to Redux, you may be left feeling instantly confused. Initially learning React, most days are spent getting comfortable with the idea of passing props from one component, to another, to another... to another.... to.... another.

While this is an easy concept to understand, it's not necessarily the most efficient. There are a variety of state management systems used within React, but I want to discuss Redux and what has helped me wrap my mind around it!

You may also like: Angular vs React vs Vue: Which one will be popular in 2020.

What is Redux?

Redux has one main advantage, and that's the efficiency it provides. Redux allows you to store your state in what is called a "Redux Store" and uses actions to call reducers, which in turn manipulate your state however you see fit.

Let's keep this simple and straight to the point. Redux is Uber Eats.

I know what you may be thinking... What are you are talking about? Let me explain.

In traditional prop passing, relate each component to a neighbor. If you needed something from the grocery store, imagine that you have to ask neighbor E, to ask neighbor D, to ask neighbor C, to ask neighbor B, to ask neighbor A, if you can use some of their bread. It works... but, it's pretty inconvenient

What if there was a way to just have the bread delivered straight to you?!

AH, this is where Redux shines. With the use of the Redux store, that bread (AKA state), is always available whenever you need it. No passing props, no talking to neighbors, just simply call up the store and get what you need!

The Redux Store

The Redux Store takes about 3.87 seconds to build, and is one of the easiest things to do in React. After installing Redux with your package manager of choice, simply import the function into your main component (usually index.js).

import { createStore } from 'redux'

Boom! Now you have the power, just create a store really quick! Be sure to export your reducer from it's proper file, and import it into your index.js file.

const store = createStore(yourReducerGoesHere)

Simple enough? Now your store exists in a variable called store. It takes in a reducer as well.(This is how it will manipulate the state that's held within the store. Now, let's talk about the Provider.

Providing state to your components

Provider is simple enough to remember, because it provides access the state from the store to your components. I say access, because it doesn't necessarily give your components the state just yet (this is what we have connect() for).

In that same component, you'll want to import Provider.

import { Provider } from 'react-redux' Booyah!

After that, you want to wrap your App component in that provider. Think of this as granting your application the ability to use the store. It typically looks something like this:

ReactDOM.render(
<Provider store={store}>
    <App />
</Provider>
, document.getElementById("root"));

See that sneaky little prop pass, right there? It almost forms a sentence! In the Provider we passed in the store. It can almost be read as, "Providing the store to the component". Well, that's how I read it at least! :)

Awesome, now we created a store, passed the store to the provider, which is providing that store to our application. Before seeing how we grab the state, we need to have state first! On to the reducer!

Reducing The Stress

Reducers! This is one of the powerful aspects of Redux. Essentially, I call them the execution guidelines. The reducer file will typically consist of two things: the initial state, and the reducer itself.

For example, for simplicity sake, let's say our initial state has an array of names.

const initialState = {
   names: ['Bob', 'Susan']
}

Woo! They are looking great. Now the reducer comes into play. This section can get messy, so we'll keep it extremely simple. Reducers are functions full of if...else conditions. The easier way to write this is with switch cases. To prevent confusion, I'll provide an example of both, if...else and a switch case, if you happen to be familiar with both!

Our case that modifies state will be called, 'Add Name'. However, in Redux cases, it's common practice to use all capital letters for this (kind of similar to just screaming at the reducer to do its job), so it would look like 'ADD_NAME'.

If none of the cases do match, you want to be sure to return the initialState. I know this is a lot of words, so let's see an example!

export const reducer = (state = initialState, action) {
    if (action.type === 'ADD_NAME') {
        return {
            ...state,
            names: [...names, action.payload]
        }
    } else {
        return state
    }
}

What's happening here is the reducer takes in state, and an action. State will be undefined if you don't provide it an initial state, so in this example, we assign state to initialState. The action will be an object containing a type and sometimes a payload property. For example, this action object for this example may look like:

{ type: 'ADD_NAME', payload: newNameGoesHere }

The type specifies what reducer case to trigger, like instructions! The payload is just data, it can be called anything. In this case, we have a new name we want to add to the users array. So we spread the whole state object first, then spread the users array into a new array, and add the new name on to the end, this name is being referenced by the action.payload.

So back to my point, reducers are the execution guidelines. They take instruction from the action, and perform based on what action.type is called. This will make more sense in a second when we discuss actions. The payload property is just a common way of passing in the data you want to incorporate into state, it can be called anything - beanChili if you want! :D

Like I said, reducers are typically written in a switch case format, so they may look like this when you come across them:

export const reducer = (state = initialState, action) {
    switch(action.type){
        case 'ADD_NAME':
            return {
                ...state,
                names: [...names, action.payload]
            }
        default:
            return state
    }
}

This achieves the same result, just tends to be less words, the longer your code gets!

Okay, so we've covered the store, the provider, initial state, and the reducer. Now let's take a peek at actions!

Lights, Camera, ACTIONS

As I stated earlier, actions are the instructions for the reducer. Action creators are functions, that return actions. These actions are objects similar to the one I referenced above, with a type and a payload property.

The way these work, is your action creator function is called within your component, which returns an object of "instructions". In this case, you call the action, and it will return an object that looks like:

{ type: 'ADD_NAME', payload: newName }

This function could be represented by:

export const addName = (newName) => {
   return { type: 'ADD_NAME', payload: newName }
}

In this case, when the addName function is invoked, we will pass in the name we want to add, as newName!

Now, this returned object gets passed into the reducer. Can you tell what's going to happen?

The reducer enters the switch case, and checks the action.type. OH! The type is 'ADD_NAME', so hop into that return statement.

Okay, so it is returning state, and then attaching action.payload onto the enter of the array... what is action.payload?

Well, referencing our object above, we see action.payload is the newName. Let's say that we passed in the name 'Chris' as the newName argument. What happens now, is Chris is tacked onto the end of the array. Now our users array in state looks like:

['Bob', 'Susan', 'Chris'] Awesome!

So essentially we just called a function (an action creator), which said, "Hey Reducer... add a new name, the new name is Chris!"

The reducer responds, "Cool, added the name, here's your new state!"

Simple enough, right? They definitely get more complex as more functionality is incorporated into your application, but these are the basics.

However, there is one final question:

How do the components actually access this state?

Simple! By connect! Let's take a look.

Connecting the links

Connecting the store state to our components becomes a bit of extra work, but essentially we have our state, and provide access to the main component (App.js). However, now we need to accept access, via the connect() method.

Connect is a higher-order component, which is a different topic itself, but essentially this gets invoked twice in a row. It is called during the export of your component.

First, let's import connect into our component:

import { connect } from 'react-redux';

Say we have a <List /> component being rendered in App.js, and we want to connect List.js. In that component, on the export line we could do something like:

export default connect(null, {})(List);

The first invocation takes in two items, the state you're receiving, and the actions you want to use (in that order). Let's touch on the state.

Remember, connecting only accepts access, it doesn't actually provide the state, that's what we have mapStateToProps for. :D

mapStateToProps says, "Oh, you connected your component? You granted access? Well here is the state you asked for!"

Okay... Maybe the component doesn't talk, but if they did, they'd probably say something along those lines.

This mapStateToProps example, is a function that receives the state, and is then passed into the connect method. Like this:

const mapStateToProps = state => {
   return {
      names: state.names 
   }
}

This function takes in state, which is the entire state object from the reducer. In this case, our state object only has one array inside of it, but these state objects are typically 10x as long, so we have to specify what information we want!

In this return line, we say, "Return an object with a names property." How do we know what names is? Well, we access it off of the state object, by state.names.

Our returned property doesn't need to be called names, we could do something like:

const mapStateToProps = state => {
   return {
      gummyBears: state.names
   }
}

But, that's not very semantic is it? We want to understand that names is an array of names. So it's common practice to keep the same property name, in your returned state object!

We're almost finished, so hang in there! Let's recap where we're at.

We have our component accessing state from the store, through mapStateToProps. The state exists in the component now, but the component can't access it just yet.

First, we need to pass it to the connect function. The connect functions says, "Access to the store granted! Now... what state am I granting access to?"

So we pass in the function returning state, mapStateToProps, like this:

export default connect(mapStateToProps, {})(List) Radical!

We're almost there!

Now the component is capable of receiving that state as props, like it traditionally would from a parent component. Maybe we are mapping over it, and displaying each name on the screen in a div. Here's what this may look like!

const List = props => {
    return (
        <div>
            {
                props.names.map(name => {
                    return <div>{name}</div>
                })
            }
        </div>
    )
}

Awesome! But there is one final problem... Where does the action get called?

Typically there would be an input, so you could input a new name, and add it to the array - but, for simplicity sake, let's just add a button that adds the name Chris, when clicked! (Not very functional, but you see my point! :D)

We need to access that action creator function. Well, earlier we exported that function so we could import it where we need it, like in our List.js component!

import { addName } from "../actions"

The file location will depend on your directory structure, but it is common to have all actions exported from an index.js file in your actions directory, and then import from that directory. Don't worry too much about that now though!

Great, we have our function, but we can't just pass this function as props to our component just yet. This action is related to Redux, and with Redux we need to connect the action through the connect higher-order component, so when we return our action object, our reducer can accept it and perform accordingly!

Remember that extra space in the connect at the bottom of our List.js component? Let's fill that in with our addName function.

export default connect(mapStateToProps, {addName})(List);

Now, we can pass in our function as props (similar to our state), and use the function as we need!

const List = props => {
    return (
        <div>
            <button onClick={() => props.addName('Chris')}></button>
            {
                props.names.map(name => {
                    return <div>{name}</div>
                })
            }
        </div>
    )
}

I simply created a button, and added an onClick event listener, which triggers the addName function, and passing in 'Chris', like we set out to achieve!

Geez! that was a mission... but we made it! So, let's recap what is happening exactly.

The Redux Recap

We started with creating our store, and passed access to it through the provider, which wrapped our application. Then we created our initial state to use, and formed our reducer which manipulates the state. We built an action creator, addName which is a function that returns instructions for the reducer. These specific instructions said, "We want to add the name Chris to the names array!"

The reducer then takes that information and adds the name to the state. Our component accesses the state through connect, and receives the state through the mapStateToPropsfunction. We also import our action creator, addName, and pass it to connect as well.

The result? We can access our action creator, and our state, as props! However, we aren't passing this information through any other components, just pulling it directly from the store. Delivery straight to your door! Uber eats roc- I mean, Redux rocks!

I understand there is so much more to Redux, and many other things you can change to make everything easier and simpler to use, I just wanted to cover some of the basic foundations of it, and what has helped me understand it a bit better!

I would love to hear your thoughts/opinions on Redux. Thank you for reading !