useReducer with useContext Part 2
Add to favorites
Incorporate useReducer with useContext
React Hooks Handbook
1
Intro to React Hooks
3:39
2
Create your first React app
4:23
3
React Component
2:54
4
Styling in React
5:06
5
Styles and Props
2:22
6
Understanding Hooks
3:21
7
useState Hook
2:54
8
useEffect Hook
3:41
9
useRef Hook
3:00
10
Props
3:11
11
Conditional Rendering
4:21
12
Load Local Data
4:04
13
Fetch Data from an API
5:40
14
Toggle a state
4:05
15
useInput Hook
6:04
16
Gatsby and React
6:44
17
NextJS and React
5:24
18
React TypeScript Part 1
8:19
19
React TypeScript Part 2
7:35
20
useScrollPosition Hook
4:26
21
useOnScreen hook
8:08
22
useContext Hook
8:32
23
Fragments
2:43
24
Lazy Loading
4:05
25
React Suspense
3:13
26
Environment Variables
4:43
27
Reach Router
5:31
28
URL Params
4:04
29
SEO and Metadata
6:47
30
Favicon
3:03
31
Dynamic Favicon
2:14
32
PropTypes
3:54
33
Custom PropTypes
3:58
34
useMemo Hook
4:05
35
forwardRef Hook
3:28
36
Handling Events
5:44
37
Spread attributes
3:35
38
useMousePosition Hook
4:55
39
useReducer with useContext Part 1
7:33
40
useReducer with useContext Part 2
6:48
41
useReducer with useContext Part 3
5:43
42
Netlify
5:08
43
Gatsby Cloud
6:19
44
Gatsby Plugin Image
8:11
45
useOnClickOutside Hook
6:32
46
useWindowSize Hook
4:14
47
usePageBottom hook
4:48
48
useLocalStorage Hook
5:27
49
Three.js in React Part 1
17:33
50
Three.js in React Part 2
11:18
CodeSandbox Links
If you haven't, I highly encourage you to follow the first part of this tutorial and fork the starter project for this tutorial. You can also access the complete code of this tutorial, with styling, at https://codesandbox.io/s/usereducer-hook-swkwl.
Create the provider
Back in ShopContext.js , add the shopReducer to the imports from the shopReducer file.
// ShopContext.js
import shopReducer, { initialState } from "./shopReducer";
Now, let's create our provider add the bottom of the ShopContext file. If you remember, a provider allows all its children components to subscribe to the context's changes. The ShopProvider will accept an argument, which is an object of children . Don't forget to export your provider.
// ShopContext.js
export const ShopProvider = ({ children }) => {
};
Inside of the provider, we will be using another hook from the React library: the useReducer hook. So let's add it to the imports.
// ShopContext.js
import { createContext, useReducer } from "react";
The useReducer hook is pretty similar to a useState hook. The only difference is that a useReducer requires as arguments a reducer and an initialState , and is preferred when we deal with complex state logic. Moreover, instead of setting a state ( setState ), the useReducer hook will dispatch it, meaning the state will be updated, and all the children listening to that state will be alerted.
// ShopContext.js
export const ShopProvider = ({ children }) => {
const [state, dispatch] = useReducer(shopReducer, initialState);
};
After adding the useReducer line, we'll need to create three functions inside of the provider: one for each action type we added in our switch statement inside of the reducer. Let's start with the ADDTOCART action.
// ShopContext.js, inside of ShopProvider
const addToCart = (product) => {
const updatedCart = state.products.concat(product);
updatePrice(updatedCart)
dispatch({
type: "ADD_TO_CART",
payload: {
products: updatedCart
}
});
};
In the function above, called addToCart , we take one argument, which is a product . Then, taking the state.products variable from useReducer , we are adding the product to the updatedCart variable. At the same time, we'll update the total price of the cart (see function below). Finally, we're dispatching the state using the dispatch from useReducer . We need to pass an object, containing a type ( ADDTOCART ), and a payload , which only contains the updated products array. We'll need to add the function for the action types REMOVEFROMCART and UPDATE_PRICE :
// ShopContext.js, inside of ShopProvider
const removeFromCart = (product) => {
const updatedCart = state.products.filter(
(currentProduct) => currentProduct.name !== product.name
);
updatePrice(updatedCart)
dispatch({
type: "REMOVE_FROM_CART",
payload: {
products: updatedCart
}
});
};
const updatePrice = (products) => {
let total = 0;
products.forEach((product) => (total += product.price));
dispatch({
type: "UPDATE_PRICE",
payload: {
total
}
});
};
Now that we have our functions, let's return something from our ShopProvider. At the bottom of the provider, let's return ShopContext.Provider . Inside of the ShopContext.Provider tags, we'll add the children argument we passed to our provider.
// ShopContext.js, inside of ShopProvider
return <ShopContext.Provider>{children}</ShopContext.Provider>;
Don't forget that a provider always requires a value prop, which is the states and functions you want to be available across your components. Let's create a value object, containing the total, products, and the three functions.
// ShopContext.js, inside of ShopProvider
const value = {
total: state.total,
products: state.products,
addToCart,
removeFromCart,
};
Let's pass the value as a prop to the ShopContext.Provider tag.
// ShopContext.js, inside of ShopProvider
return <ShopContext.Provider value={value}>{children}</ShopContext.Provider>;
Create the useContext
We're almost there! This is the last step when creating a context, which is creating a useContext hook. Import useContext from the React imports.
// ShopContext.js
import { createContext, useReducer, useContext } from "react";
Create the useShop custom hook, which derives from useContext. Learn more about it in the useContext section of this handbook.
const useShop = () => {
const context = useContext(ShopContext)
if (context === undefined) {
throw new Error("useShop must be used within ShopContext")
}
return context
}
export default useShop
Use the provider
In App.js, import ShopProvider from the ShopContext file.
// App.js
import { ShopProvider } from "./ShopContext"
Wrap all the content in ShopProvider tags.
const App = () => {
return (
<ShopProvider>
{ /* App content here... */ }
</ShopProvider>
);
};
Upcoming
Great! We finished coding our context using useReducer . We also wrapped our entire application in our ShopProvider , ready for all its children components to use the context! In the next section, we'll be adding the functionality to our website - in other words, we'll connect the functions we added in the provider to the frontend. See you in the next section !
Learn with videos and source files. Available to Pro subscribers only.
Purchase includes access to 50+ courses, 320+ premium tutorials, 300+ hours of videos, source files and certificates.
Templates and source code
Download source files
Download the videos and assets to refer and learn offline without interuption.
Design template
Source code for all sections
Video files, ePub and subtitles
Browse all downloads
1
Intro to React Hooks
An overview of React Hooks and the frameworks you can use to build your React application blazingly fast
3:39
2
Create your first React app
Create your first React project from the Terminal and save it on your local computer
4:23
3
React Component
Create your first JSX component using React
2:54
4
Styling in React
How to style your React components using inline styling, separate stylesheets or styled-components
5:06
5
Styles and Props
Render different styles depending on different properties passed to your component
2:22
6
Understanding Hooks
Learn about the basics of React Hooks, which introduced at React Conf 2018
3:21
7
useState Hook
Use the useState hook to manage local state in your React component
2:54
8
useEffect Hook
Manage with your component's lifecycle with the useEffect hook
3:41
9
useRef Hook
Learn about the useRef hook, which replaces the JavaScript getElementById way
3:00
10
Props
Learn about props in React to pass data from parent to child components
3:11
11
Conditional Rendering
Render different UIs depending on different conditions and states
4:21
12
Load Local Data
Load local JSON data into your React application
4:04
13
Fetch Data from an API
Learn the basics of asynchronous functions and promises by fetching data from an API using fetch, useEffect and useState
5:40
14
Toggle a state
Learn how to toggle a state from true to false and back again
4:05
15
useInput Hook
Create a hook to get the value and the onChange event of input fields
6:04
16
Gatsby and React
Create a static content-oriented website using React on Gatsby
6:44
17
NextJS and React
Create your first NextJS React application
5:24
18
React TypeScript Part 1
Learn how to create a React TypeScript application using the Create React App, Gatsby and NextJS methods
8:19
19
React TypeScript Part 2
Learn the basics of TypeScript and how to use TypeScript in a React component
7:35
20
useScrollPosition Hook
Create a custom hook to listen to the current window position of the user
4:26
21
useOnScreen hook
Create a custom hook to listen to when an element is visible on screen
8:08
22
useContext Hook
Manage global states throughout the entire application
8:32
23
Fragments
Group multiple children together with React Fragments
2:43
24
Lazy Loading
Lazy Load heavy components to improve performance
4:05
25
React Suspense
Wait for data with React Suspense and React.lazy
3:13
26
Environment Variables
Make environment variables secret with a .env file
4:43
27
Reach Router
Create a multiple-pages React application with Reach Router
5:31
28
URL Params
Create unique URL with URL Params
4:04
29
SEO and Metadata
Optimize a React application for search engines with React Helmet
6:47
30
Favicon
Add an icon to a React website
3:03
31
Dynamic Favicon
Change the favicon's fill color depending on the user's system appearance
2:14
32
PropTypes
Implement props type-checking with PropTypes
3:54
33
Custom PropTypes
Create a custom PropType using a validator function
3:58
34
useMemo Hook
Prevent unnecessary re-renders when the component stays the same
4:05
35
forwardRef Hook
Forward a ref to a child component
3:28
36
Handling Events
How to handle events in React
5:44
37
Spread attributes
Learn how to make use of the spread operator
3:35
38
useMousePosition Hook
Detect the user's mouse position on a bound element
4:55
39
useReducer with useContext Part 1
Create a reducer to be used in a context
7:33
40
useReducer with useContext Part 2
Incorporate useReducer with useContext
6:48
41
useReducer with useContext Part 3
Connect the context and reducer with the frontend
5:43
42
Netlify
Deploy to production using Netlify
5:08
43
Gatsby Cloud
Deploy to production using Gatsby Cloud
6:19
44
Gatsby Plugin Image
Use gatsby-plugin-image for automatic image resizing, formatting, and higher performance
8:11
45
useOnClickOutside Hook
Toggle a modal visibility with a useOnClickOutside hook
6:32
46
useWindowSize Hook
Create a hook to determine the width and height of the window
4:14
47
usePageBottom hook
Detect if the user scrolled to the bottom of the page
4:48
48
useLocalStorage Hook
Store an item in a browser's local storage
5:27
49
Three.js in React Part 1
Bring your website to life with beautiful 3D objects
17:33
50
Three.js in React Part 2
Bring your website to life with beautiful 3D objects
11:18
Meet the instructor
We all try to be consistent with our way of teaching step-by-step, providing source files and prioritizing design in our courses.
Stephanie Diep
iOS and Web developer
Developing web and mobile applications while learning new techniques everyday
7 courses - 36 hours
Build Quick Apps with SwiftUI
Apply your Swift and SwiftUI knowledge by building real, quick and various applications from scratch
11 hrs
Advanced React Hooks Handbook
An extensive series of tutorials covering advanced topics related to React hooks, with a main focus on backend and logic to take your React skills to the next level
3 hrs
SwiftUI Concurrency
Concurrency, swipe actions, search feature, AttributedStrings and accessibility were concepts discussed at WWDC21. This course explores all these topics, in addition to data hosting in Contentful and data fetching using Apollo GraphQL
3 hrs
SwiftUI Combine and Data
Learn about Combine, the MVVM architecture, data, notifications and performance hands-on by creating a beautiful SwiftUI application
3 hrs
SwiftUI Advanced Handbook
An extensive series of tutorials covering advanced topics related to SwiftUI, with a main focus on backend and logic to take your SwiftUI skills to the next level
4 hrs
React Hooks Handbook
An exhaustive catalog of React tutorials covering hooks, styling and some more advanced topics
5 hrs
SwiftUI Handbook
A comprehensive series of tutorials covering Xcode, SwiftUI and all the layout and development techniques
7 hrs