Deploy smart contract using Hardhat#

Introduction#

This section will guide you through deploying an ERC20 to the POTOS Network using Hardhat.

ERC-20 defines a standard for Fungible Tokens, meaning that each Token has a property that makes it be exactly the same (in type and value) as any other Token.

Hardhat is a smart-contract development environment that will help you:

  • Develop and compile smart contracts and DApp.

  • Debug, test, and deploy smart contracts and DApps.

By the end of this guide you will be able to:

  • Set up a Hardhat project on POTOS.

  • Create a simple ERC20 token.

  • Compile your smart contract using Hardhat.

  • Test, deploy, and interact with your smart contract using Hardhat.

  • Explore Hardhat forking feature.

Prerequisites#

To follow this tutorial, the following are the prerequisites:

  • Code editor: a source-code editor such VSCode.

  • Metamask: used to deploy the contracts, sign transactions and interact with the contracts.

  • Hardhat Requirements: environment required in Hardhat.

Step 1: Initialize an Hardhat project#

Copy and paste the following code into Terminal to create a project:

mkdir bcos-hardhat-erc20
cd bcos-hardhat-erc20

# init npm project
npm init -y
# install hardhat
npm install --save-dev hardhat

Paste the code below to install other dependencies.

npm install dotenv @openzeppelin/contracts

In the same directory where you installed Hardhat run:

npx hardhat init

Select Create a JavaScript project option and an empty hardhat.config.js with your keyboard and hit enter.

$ npx hardhat init
888    888                      888 888               888
888    888                      888 888               888
888    888                      888 888               888
8888888888  8888b.  888d888 .d88888 88888b.   8888b.  888888
888    888     "88b 888P"  d88" 888 888 "88b     "88b 888
888    888 .d888888 888    888  888 888  888 .d888888 888
888    888 888  888 888    Y88b 888 888  888 888  888 Y88b.
888    888 "Y888888 888     "Y88888 888  888 "Y888888  "Y888

👷 Welcome to Hardhat v2.22.13 👷‍

✔ What do you want to do? · Create a JavaScript project
✔ Hardhat project root: · /opt/bcos-hardhat-erc20
✔ Do you want to add a .gitignore? (Y/n) · y
✔ Do you want to install this sample project's dependencies with npm (@nomicfoundation/hardhat-toolbox)? (Y/n) · y

After initializing a hardhat project, your current directory should include:

contracts/ – this folder contains smart contract code.

scripts/ – this folder contains code that is responsible for deploying your contracts onto the blockchain network.

test/ – this folder contains all unit tests for your smart contract.

hardhat.config.js – this file contains configurations necessary for the work of Hardhat and the deployment of the soul-bound token.

Step 2: Setup Hardhat Configs#

Next, create your .env file in the project folder to load environment variables into process.env.

Paste this command in your terminal to create the .env file:

touch .env

Configure your .env file to look like this:

 BCOS_URL= "Your BCOS URL"
 PRIVATE_KEY= "your private key copied from MetaMask wallet"

Modify your hardhat.config.js with the following configurations:

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


module.exports = {
  solidity: "0.8.27",
  networks: {
    bcos: {
      url: process.env.BCOS_URL || "",
      gasPrice: 30000000,
      accounts:
        process.env.PRIVATE_KEY !== undefined ? [process.env.PRIVATE_KEY] : [],
    }
  }
};

Now that you have your development environment all set, let’s get into writing an ERC20 token smart contract.

Step 3: Create ERC20 Contract#

Create a contract code file MyToken.sol in contracts/ directory:

// SPDX-License-Identifier: Apache 2.0
pragma solidity ^0.8.20;

import "@openzeppelin/contracts/token/ERC20/ERC20.sol";
import "@openzeppelin/contracts/token/ERC20/extensions/ERC20Permit.sol";

contract MyToken is ERC20, ERC20Permit {
    constructor() ERC20("MyToken", "MTK") ERC20Permit("MyToken") {}

    function mint(uint256 value) public {
        _mint(msg.sender, value);
    }
}

Step 4: Compile your contract#

Run npx hardhat compile in your terminal to compile the contract. The compile task is one of the built-in tasks.

$ npx hardhat compile

Downloading compiler 0.8.27
Compiled 19 Solidity files successfully (evm target: paris).

Step 5: Testing contracts#

Create a new directory called test within your project’s root directory, and then create a new file called MyToken.js in the directory.

mkdir -p test
cd test
touch MyToken.js

Paste the following code into MyToken.js. We’ll explain this code in more detail later.

const { expect } = require("chai");

describe("Token contract", function () {
  it("Deployment should assign the total supply of tokens to the owner", async function () {
    const [owner] = await ethers.getSigners();

    const hardhatToken = await ethers.deployContract("MyToken");

    await hardhatToken.mint(10000);
    const ownerBalance = await hardhatToken.balanceOf(owner.address);
    expect(await hardhatToken.totalSupply()).to.equal(ownerBalance);
  });
});

Run npx hardhat test in Terminal. You should see the following output:

$ npx hardhat test

  Token contract
    âś” Deployment should assign the total supply of tokens to the owner

  1 passing (382ms)

Step 6: Deploy contracts#

In the Explorer pane, select the “scripts” folder and click the New File button to create a new file named deploy.js that contains the following code. Scripts are JavaScript/Typescript files that help you deploy contracts to the blockchain network.

const { ethers } = require("hardhat");

async function main() {

  const deployerAddr = "[Your Metamask wallet address]";
  const deployer = await ethers.getSigner(deployerAddr);

  console.log(`Deploying contracts with the account: ${deployer.address}`);
  console.log(`Account balance: ${(await deployer.provider.getBalance(deployerAddr)).toString()}`);


  const token = await ethers.deployContract("MyToken");
  await token.waitForDeployment();

  console.log(`Congratulations! You have just successfully deployed your ERC20 tokens.`);
  console.log(`ERC20 contract address is ${token.target}.`);
}

main().catch((error) => {
  console.error(error);
  process.exitCode = 1;
});

Run the following command in Terminal, which tells Hardhat to deploy your ERC20 token on the BCOS Network.

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

Deploying contracts with the account: 0xEc5E7dEc9d2d6bfA1f2221aCE01aE3deb6906fb0
Account balance: 100000000000000000000000
Congratulations! You have just successfully deployed your ERC20 tokens.
ERC20 contract address is 0xAd384DC5c3aE98460A8969770373001783963c13.