Building Web3 Apps with Next.js and Ethereum: A Comprehensive Guide

Next.js is a powerful framework for building server-side rendered React applications. It offers a lot of features out of the box, including automatic code splitting, server-side rendering, and easy setup for static file serving. In addition to these features, Next.js is also a great choice for building web3 applications that interact with the Ethereum blockchain.

Table of Contents

In this post, we’ll explore how to use Next.js to build a web3 app with Ethereum and Solidity. We’ll cover the necessary tools, how to write and deploy a smart contract, how to interact with the Ethereum blockchain using Web3.js, how to connect to MetaMask, and how to deploy your app to a hosting service.

Install Next.js

Before we can start building our web3 app, we need to install Next.js. You can do this by running the following command:

lua
npm install next

This will install the latest version of Next.js and its dependencies in your project.

Set up a Next.js project

Next, we’ll set up a new Next.js project. You can do this by running the following command:

lua
npx create-next-app my-web3-app

This will create a new Next.js project in a directory called my-web3-app. Once the installation is complete, you can start the development server by running the following command:

arduino
npm run dev

This will start a development server at http://localhost:3000, where you can see your app running.

Write a smart contract

The first step in building a web3 app is to write a smart contract. Smart contracts are self-executing contracts with the terms of the agreement between buyer and seller being directly written into lines of code. Solidity is the most popular language for writing smart contracts on the Ethereum blockchain.

Here’s an example of a simple smart contract written in Solidity:

typescript

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.0;

contract MyContract {
uint256 private _myNumber;

function setNumber(uint256 number) public {
_myNumber = number;
}

function myNumber() public view returns (uint256) {
return _myNumber;
}
}


This contract defines a private variable called _myNumber and two functions called setNumber and myNumber. The setNumber function sets the value of _myNumber, and the myNumber function returns the value of _myNumber.

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Interact with the smart contract using Web3.js

Next, we’ll use Web3.js to interact with our smart contract. Web3.js is a JavaScript library that allows you to interact with the Ethereum blockchain. We can use Web3.js to create a new instance of our contract, and then call its functions to interact with it.

Here’s an example of how you can create a new instance of your contract using Web3.js:

javascript

import Web3 from 'web3';
import MyContract from '../contracts/MyContract.json';

const web3 = new Web3(window.ethereum);

const contract = new web3.eth.Contract(
MyContract.abi,
'0x1234567890123456789012345678901234567890'
);


This code creates a new instance of the Web3.js library, and then uses it to create a new instance of our smart contract. We pass in the contract's ABI (Application Binary Interface) and its address as arguments to the web3.eth.Contract constructor. You can find the contract's ABI and address in the JSON file generated by the Solidity compiler. Once you've created this instance, you can use it to interact with your smart contract.

Connect to MetaMask

MetaMask is a popular Ethereum wallet that allows users to manage their Ethereum accounts and interact with dApps (decentralized applications). We can use MetaMask to connect our Next.js app to the Ethereum blockchain.

To connect to MetaMask, we’ll need to add the following code to our app:

javascript

import { useEffect } from 'react';
import Web3 from 'web3';

function MyApp({ Component, pageProps }) {
useEffect(() => {
if (typeof window.ethereum !== 'undefined') {
window.ethereum.request({ method: 'eth_requestAccounts' });
}
}, []);

return <Component {...pageProps} />;
}

export default MyApp;

This code adds an useEffect hook to our MyApp component that checks if MetaMask is installed and prompts the user to connect their wallet if it is. When the user clicks the connect button in MetaMask, the eth_requestAccounts method is called, which allows us to access their Ethereum account and interact with the blockchain.

Deploy your app

Finally, we’ll deploy our Next.js app to a hosting service. There are many hosting services available, but one popular option for deploying web3 apps is Heroku.

To deploy your app to Heroku, you’ll need to create a Heroku account and install the Heroku CLI. Once you’ve done that, you can use the following commands to deploy your app:

css
heroku login
heroku create
git push heroku main

These commands will log you in to your Heroku account, create a new Heroku app, and deploy your app to the Heroku server.

Conclusion

In this post, we’ve explored how to use Next.js to build a web3 app with Ethereum and Solidity. We’ve covered the necessary tools, how to write and deploy a smart contract, how to interact with the Ethereum blockchain using Web3.js, how to connect to MetaMask, and how to deploy your app to a hosting service. With these skills, you’ll be able to build your own decentralized applications and interact with the Ethereum ecosystem.