Module Project: Context API - Shopping Cart

In this module you will take your newfound knowledge of Context API and refactor a e-commerce store to use Context API as well as extend the functionality of the application making it more robust!

Introduction

Read these instructions carefully. Understand exactly what is expected before starting this project.

Commits

Commit your code regularly and meaningfully. This helps both you and your team lead in case you ever need to return to old code for any number of reasons.

Description

In this project you'll take take an almost completed e-commerce store and refactor the application to use the Context API.

Instructions

Task 1: Project Set up

Create a forked copy of this project.
Add your team lead as collaborator on Github.
Clone your OWN version of the repository in your terminal.
CD into the project base directory cd react-shopping-cart.
Download project dependencies by running npm install.
Start up the app using npm start.

Task 2: MVP

Before you get started, please take a few minutes and get acquainted with this application. Understand what's going on and how it's working.

If you look in the App.js you'll notice there are currently two state properties - products to keep track of all available products, and cart that will keep track of all the items in our cart.
You'll also notice inside of our App.js we have 3 components. A navigation component and two route based components. Each of those components are all being passed either our cart state or product state as props, when we start to scale our application and add more props our codebase is going to start to become very cumbersome and will make our application hard to work with.
To combat this from happening we're going to refactor our application to use Context API, making it easier and more effiecent to access data across our application.

Step 1 - Add item functionality

In App.js there is a function called addItem. Finish writing the logic in this function to be able to add the given item to the shopping cart

STEP 2 - Creating ProductContext

In src, create a new folder named contexts, this folder is going to be used to hold all of context objects we create.
Inside that folder create a new file named ProductContext.js
In this file, import the createContext function from the react library and create our ProductContext.

STEP 3 - Providing data with ProductContext

Now that we've created our ProductContext we can import into our App.js. Now we can start providing data across our application!
Wrap all of your components/routes in App.js inside of ProductContext.Provider component.
Next pass a value prop to your Provider.
In the value prop we'll pass in the products state, and an addItem function that will allow us to add books to the cart.

<ProductContext.Provider value={{ products, addItem }}>

Now that we're providing our products state and addItem function we can simplify our products route a bit.

Before

<Route exact path="/">
  <Products products={products} addItem={addItem} />
</Route>

After

<Route exact path="/">
  <Products />
</Route>

After refactoring you'll notice a few errors... Don't worry we'll clean those up shortly!

STEP 4 - Consuming data with ProductContext

Now that our ProductContext is now providing data we can finally consume it! To do so let's head over to our Products component and import the useContext hook as well as our ProductContext.
In the component, call the useContext hook and pass in the context object we want to use into it.
When we do this, useContext is going to return value passed by our ProductContext Provider value prop. In our case we're getting back an object with two properties. A products property and a addItem property. We can go ahead and destructure those.

const { products, addItem } = useContext(ProductContext);

Now that we have all of the data we need we can refactor our Products component from using props.
To do so we just need to remove every instance of props.
- Remove it from the function parameters
- Remove it from the products map
- Remove it from addItem prop
Now our Products component is getting it's data solely from Context API 😃.

STEP 5 - Create the CartContext

Now that we have refactored our Products component to utilize Context API let's refactor our Cart and Navigation Component to use Context API as well.
To start create a new file in our contexts folder named CartContext.js, this context is going to be utilized by our ShoppingCart and Navigation component.
Inside of our new CartContext import createContext and create a new context named CartContext.

STEP 6 - Providing data with CartContext

Let's go ahead and bring our newly created CartContext into our App.js and wrap all of our components inside of our CartContext.Provider. Make sure our ProductContext.Provider is still the root provider.
Now pass a value prop to our CartContext.Provider, this value prop is going to contain our cart state.
Now that we're providing our cart data, we can start to refactor our Navigation and ShoppingCart components.
Let's start with our ShoppingCart component first. Go ahead and refactor the ShoppingCart route to no longer use render props. This will throw us an error, but we'll be able to resolve it quickly.
While were at it let's go ahead and remove the props from our navigation as well.

STEP 7 - The final stretch

Our cart data is now being provided to us from our CartContext time to consume it!
First, let's head to our ShoppingCart component and import the useContext hook and our CartContext.
Now in the component, pass CartContext to the useContext hook and assign it to a variable named cart.
Inside of our component we now need to remove all instances of props.
- Remove the props parameter
- Remove the props portion in our getCartTotal function
- Remove props when we're mapping over our cart
Time to do the same thing for our Navigation component.
- First import the useContext hook and our CartContext
- Next, pass our CartContext to the useContext hook and assign it to a variable named cart.
- Lastly we need to remove all instances of props
  - Remove props from our parameters
  - Remove props from our cart length

We have now successfully converted our application into using Context API 🔥

MVP Requirements

Create a ProductContext and a CartContext
Use the Provider Component from ProductContext and CartContext to provide data to child components
Consume data using the useContext hook from ProductContext and CartContext

Task 3: Stretch Problems

Do not attempt stretch problems until MVP has been reached and a final commit has been made.

Create a removeItem function that allows you to remove an item from your cart with a click of a button. This removeItem function should be able to be consumed from your ShoppingCartItem component. Remember each item has an id this will help out a lot while creating your removeItem function!

prashishb/web-module-project-context