Deploy a Smart Contract with Hardhat

Deploying a Contract Using Hardhat Scripts

This tutorial will walk you through writing and compiling an ERC-721 Solidity smart contract. You'll then deploy and interact with it on the Hedera network using the Hedera Smart Contract Service (HSCS) and familiar EVM tools like Ethers.js, connecting via the JSON-RPC relay.

What you will accomplish

By the end of this tutorial, you will be able to:

  • Compile and deploy a smart contract using Hardhat

  • Interact with a smart contract using Hardhat

Note: This tutorial is currently supported only in the Getting Started JavaScript series and is not available for other languages.

Prerequisites

Before you begin, you should have completed the following tutorial:

Step 1: Project Setup

Initialize Project

Set up your Node.js project by initializing npm:

npm init -y

Install Dependencies

Next, install the required dependencies:

npm install @openzeppelin/contracts dotenv

We also need a bunch of developer dependencies to be able to deploy and interact with smart contracts through Hardhat:

npm install --save-dev @nomicfoundation/hardhat-toolbox

Create .env File

To create your .env file, you can run the below command:

touch .env

Securely store your sensitive data like the OPERATOR_KEY in a .env file. For the JSON RPC_URL, we'll use the Hashio RPC endpoint for testnet.

.env
OPERATOR_KEY=your-operator-key
RPC_URL=https://testnet.hashio.io/api

Replace the your-operator-key environment variable wiht the HEX Encoded Private Key for your ECDSA account from the Hedera Portal.

Please note: that Hashio is intended for development and testing purposes only. For production use cases, it's recommended to use commercial-grade JSON-RPC Relay or host your own instance of the Hiero JSON-RPC Relay.

Configure Hardhat

Create a hardhat.config.jsfile in the root of your project. This file contains the network settings so Hardhat knows how to interact with the Hedera Testnet. We'll use the variables you've stored in your .env file. Don't forget to import the dotenv package to load environment variables and the Hardhat Toolbox package to be able to use Hardhat scripts.

hardhat.config.js
require("dotenv").config();
require("@nomicfoundation/hardhat-toolbox");

module.exports = {
  solidity: {
    version: "0.8.22",
  },
  defaultNetwork: "testnet",
  networks: {
    testnet: {
      // HashIO RPC testnet endpoint in the .env file
      url: process.env.RPC_URL,
      // Your ECDSA account private key pulled from the .env file
      accounts: [process.env.OPERATOR_KEY],
    }
  }
};

You can verify the connection by running:

npx hardhat console --network testnet

This command launches an interactive JavaScript console connected directly to the Hedera Testnet, providing access to the Ethers.js library for blockchain interactions. If you successfully enter this interactive environment, your Hardhat configuration is correct. To exit the interactive console, press ctrl + c twice.

Step 2: Creating the ERC-721 Contract

Create a new Solidity file (erc-721.sol ) in a new contracts directory:

contracts/erc-721.sol
// SPDX-License-Identifier: MIT
// Compatible with OpenZeppelin Contracts ^5.0.0
pragma solidity ^0.8.22;

import {ERC721} from "@openzeppelin/contracts/token/ERC721/ERC721.sol";
import {Ownable} from "@openzeppelin/contracts/access/Ownable.sol";

contract MyToken is ERC721, Ownable {
    uint256 private _nextTokenId;

    constructor(address initialOwner)
        ERC721("MyToken", "MTK")
        Ownable(initialOwner)
    {}

    function safeMint(address to) public onlyOwner returns (uint256) {
        uint256 tokenId = _nextTokenId++;
        _safeMint(to, tokenId);
        return tokenId;
    }
}

This contract was created using the OpenZeppelin Contracts Wizard and OpenZeppelin's ERC-721 standard implementation with an ownership model. The ERC-721 token's name has been set to "MyToken." The contract implements the safeMint function, which accepts the address of the owner of the new token and uses auto-increment IDs, starting from 0.

Let's compile this contract by running:

npx hardhat compile

This command will generate the smart contract artifacts, including the ABI. We are now ready to deploy the smart contract.

Step 3: Deploy Your ERC-721 Smart Contract

Create a deployment script (deploy.js) in a new scripts directory:

scripts/deploy.js
async function main() {
  // Get the signer of the tx and address for minting the token
  const [deployer] = await ethers.getSigners();
  console.log("Deploying contracts with the account:", deployer.address);

  // The deployer will also be the owner of our NFT contract
  const MyToken = await ethers.getContractFactory("MyToken", deployer);
  const contract = await MyToken.deploy(deployer.address);

  console.log("Contract deployed at:", contract.target);
}

main().catch(console.error);

In this script, we first retrieve your account (the deployer) using Ethers.js. This account will own the deployed smart contract. Next, we use this account to deploy the contract by calling MyToken.deploy(deployer.address). This passes your account address as the initial owner and signer of the deployment transaction.

Deploy your contract by executing the script:

npx hardhat run scripts/deploy.js --network testnet

Copy the deployed address—you'll need this in subsequent steps.

The output looks like this:

Step 4: Minting an ERC-721 Token

Create a mint.js script in your scripts directory to mint an ERC-721 token. Don't forget to replace the <your-contract-address> with the address you've just copied.

mint.js
async function main() {
    const [deployer] = await ethers.getSigners();
    
    // Get the ContractFactory of your MyToken ERC-721 contract
    const MyToken = await ethers.getContractFactory("MyToken", deployer);
    
    // Connect to the deployed contract 
    // (REPLACE WITH YOUR CONTRACT ADDRESS)
    const contractAddress = "<your-contract-address>";
    const contract = await MyToken.attach(contractAddress);
    
    // Mint a token to ourselves
    const mintTx = await contract.safeMint(deployer.address);
    const receipt = await mintTx.wait();
    const mintedTokenId = receipt.logs[0].topics[3];
    console.log('Minted token ID:', mintedTokenId);
    
    // Check the balance of the token
    const balance = await contract.balanceOf(deployer.address);
    console.log('Balance:', balance.toString(), "NFTs");
}

main().catch(console.error);

The code mints a new NFT to your account ( deployer.address ). Then we verify the balance to see if we own an ERC-721 token of type MyToken.

Mint an NFT:

npx hardhat run scripts/mint.js --network testnet

Expected output:

Minted token ID: 0x0000000000000000000000000000000000000000000000000000000000000000 // Represents ID 0
Balance: 1 NFT

Congratulations! 🎉 You have successfully learned how to deploy an ERC-721 smart contract using Hardhat, OpenZeppelin, and Ethers. Feel free to reach out in Discord!

Next Steps

PreviousDeploy a Smart Contract with RemixNextTutorials

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