Deploy a Smart Contract Using Hardhat

In this tutorial, you'll be guided through setting up a Hardhat project and deploying a Hedera smart contract to the Hedera Testnet using the Hashio JSON-RPC instance.

Hardhat is a development environment for Ethereum smart contracts. It consists of different components for editing, compiling, debugging, and deploying your smart contracts and dApps, all working together to create a complete development environment. By the end of this tutorial, you'll have learned how to deploy smart contracts using Hardhat on the Hedera Testnet**.**

1. PREREQUISITES

2. HARDHAT SETUP

3. PROJECT CONTENTS

4. DEPLOY CONTRACT

Prerequisites

• Basic understanding of smart contracts.

• Basic understanding of Node.js or Javascript.

• Basic understanding of the Hedera JSON RPC Relay.

• Basic understanding of Hardhat Ethereum Development Tool.

Hardhat Project Setup

To make the setup process simple, you'll use a pre-configured Hardhat project from the hedera-hardhat-example-project repository.

Open a terminal window and navigate to your preferred directory where your Hardhat project will live. Run the following command to clone the repo and install dependencies to your local machine:

git clone https://github.com/hashgraph/hedera-hardhat-example-project.git
cd hedera-hardhat-example-project
npm install

The dotenv package is used to manage environment variables in a separate .env file, which is loaded at runtime. This helps protect sensitive information like your private keys and API secrets, but it's still best practice to add .env to your .gitignore to prevent you from pushing your credentials to GitHub.

Project Configuration

In this step, you will update and configure the Hardhat configuration file that defines tasks, stores Hedera account private key information, and Hashio Testnet RPC URL. First, rename the .env.example file to .env. and update the .env and hardhat.config.js files with the following code.

But first, in order to deploy the contract to the Hedera Testnet, you will need to get a testnet account and key. To get a testnet account, create an ECDSA account using the Hedera Developer Portal. Once you have your ECDSA account and HEX encoded private key, add the private key to the TESTNET_OPERATOR_PRIVATE_KEY variable in the .env file.

Create your testnet account 🛠️

Create Hedera Portal Profile (Faucet)

The Hedera Testnet account allows you to interact with our APIs and pay for the transaction fees. Visit the Hedera portal to create your Hedera Testnet account and follow the instructions.

Once you have completed the instructions, you will receive a Hedera Testnet account ID (0.0.x) and your private/public key pair on your testnet page. You will need to copy over your ECDSA HEX Encoded private key and paste it in the TESTNET_OPERATOR_PRIVATE_KEY .env file variable.

Note: Your Hedera Testnet account will be credited with 10,000 test HBAR upon creation that can only be utilized on the Hedera test network. Your balance will be topped up daily to 10,000 test HBAR when you use your funds.

Environment Variables

The .env file defines environment variables used in the Hardhat configuration file. The TESTNET_OPERATOR_PRIVATE_KEY variable contains the ECDSA Hex Encoded Private Key for the Hedera Testnet account used in the testnet network Hardhat configuration.

The TESTNET_ENDPOINT variable contains the HashIO Testnet endpoint URL. This is the JSON-RPC instance that will submit the transactions to the Hedera test network to test, create and deploy your smart contract.

# operator/receiver keys referenced in the hardhat.config account variable
TESTNET_OPERATOR_PRIVATE_KEY=0xb46751179bc8aa9e129d34463e46cd924055112eb30b31637b5081b56ad96129

# testnet endpoint referenced in the hardhat.config url variable
TESTNET_ENDPOINT='https://testnet.hashio.io/api'

Hardhat Configuration

The hardhat.config.js file defines tasks for Hardhat, including show-balance, transfer-hbars, deploy-contract, contract-view-call, and contract-call. It exports a configuration object that includes the Solidity version and settings, default network, and network settings for the testnet network.

The url property is set to the TESTNET_ENDPOINT environment variable, and accounts to an array containing the testnet private key imported from the .env file.

require("@nomicfoundation/hardhat-toolbox");
require("@nomicfoundation/hardhat-chai-matchers");
require("@nomiclabs/hardhat-ethers");
//import dotenv library to access environment variables stored in .env file
require("dotenv").config();

//define hardhat task here, which can be accessed in our test file (test/rpc.js) by using hre.run('taskName')
task("show-balance", async () => {
  const showBalance = require("./scripts/showBalance");
  return showBalance();
});

task("deploy-contract", async () => {
  const deployContract = require("./scripts/deployContract");
  return deployContract();
});

task("contract-view-call", async (taskArgs) => {
  const contractViewCall = require("./scripts/contractViewCall");
  return contractViewCall(taskArgs.contractAddress);
});

task("contract-call", async (taskArgs) => {
  const contractCall = require("./scripts/contractCall");
  return contractCall(taskArgs.contractAddress, taskArgs.msg);
});

/** @type import('hardhat/config').HardhatUserConfig */
module.exports = {
  mocha: {
    timeout: 3600000,
  },
  solidity: {
    version: "0.8.9",
    settings: {
      optimizer: {
        enabled: true,
        runs: 500,
      },
    },
  },
  //this specifies which network should be used when running Hardhat tasks
  defaultNetwork: "testnet",
  networks: {
    testnet: {
      //HashIO testnet endpoint from the TESTNET_ENDPOINT variable in the project .env the file
      url: process.env.TESTNET_ENDPOINT,
      //the Hedera testnet account ECDSA private
      //the public address for the account is derived from the private key
      accounts: [
        process.env.TESTNET_OPERATOR_PRIVATE_KEY,
      ],
    },
  },
};

Project Contents

In this step, you'll look at the descriptions of the Hardhat project contents. For more information regarding Hardhat projects, check out the Hardhat docs. If you do not need to review the project contents you can skip to "Test and Deploy."

contracts/

The contracts/ folder contains the source file for the Greeter smart contract. Let's review the Greeter.sol smart contract in the hedera-example-hardhat-project/contracts folder. At the top of the file, the SPDX-License-Identifier defines the license, in this case, the MIT license. The pragma solidity ^0.8.9; line specifies the Solidity compiler version to use. These two lines are crucial for proper licensing and compatibility.

//SPDX-License-Identifier: MIT
pragma solidity ^0.8.9;

contract Greeter {
    string private greeting;

    event GreetingSet(string greeting);

    //This constructor assigns the initial greeting and emit GreetingSet event
    constructor(string memory _greeting) {
        greeting = _greeting;

        emit GreetingSet(_greeting);
    }

    //This function returns the current value stored in the greeting variable
    function greet() public view returns (string memory) {
        return greeting;
    }

    //This function sets the new greeting msg from the one passed down as parameter and emit event
    function setGreeting(string memory _greeting) public {
        greeting = _greeting;

        emit GreetingSet(_greeting);
    }
}

NOTE: The pragma solidity line must match the version of Solidity defined in the module exports of your hardhat.config.js file.

scripts/

The scripts/ folder contains the automation scripts for the test file. This project contains 4 scripts.

The scripts/ folder contains test scripts for locally testing a smart contract before deploying it. Please read the comments to help you understand the code and its purpose:

contractCall.js

Calls the setGreeting function from the Greeter contract and sets the greeter message to "Greeter."\

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

//This function accepts two parameters - address and msg
//Retrieves the contract from the address and set new greeting
module.exports = async (address, msg) => {

  //Assign the first signer, which comes from the first privateKey from our configuration in hardhat.config.js, to a wallet variable. 
  const wallet = (await ethers.getSigners())[0];

  //Assign the greeter contract object in a variable, this is used for already deployed contract, which we have the address for. ethers.getContractAt accepts:
  //name of contract as first parameter
  //address of our contract
  //wallet/signer used for signing the contract calls/transactions with this contract 
  const greeter = await ethers.getContractAt('Greeter', address, wallet);

  //using the greeter object(which is our contract) we can call functions from the contract. In this case we call setGreeting with our new msg
  const updateTx = await greeter.setGreeting(msg);

  console.log(`Updated call result: ${msg}`);

  return updateTx;
};

contractViewCall.js

Returns the current greeter message value stored with the Greeter contract.\

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

module.exports = async (address) => {
  //Assign the first signer, which comes from the first privateKey from our configuration in hardhat.config.js, to a wallet variable.
  const wallet = (await ethers.getSigners())[0];

  //Assign the greeter contract object in a variable, this is used for already deployed contract, which we have the address for. ethers.getContractAt accepts:
  //name of contract as first parameter
  //address of our contract
  //wallet/signer used for signing the contract calls/transactions with this contract
  const greeter = await hre.ethers.getContractAt("Greeter", address, wallet);
  //using the greeter object(which is our contract) we can call functions from the contract. In this case we call greet which returns our greeting msg
  const callRes = await greeter.greet();

  console.log(`Contract call result: ${callRes}`);

  return callRes;
};

deployContract.js

Deploys the Greeter contract and returns the contract public address. \

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

module.exports = async () => {
  //Assign the first signer, which comes from the first privateKey from our configuration in hardhat.config.js, to a wallet variable.
  let wallet = (await ethers.getSigners())[0];

  //Initialize a contract factory object
  //name of contract as first parameter
  //wallet/signer used for signing the contract calls/transactions with this contract
  const Greeter = await ethers.getContractFactory("Greeter", wallet);
  //Using already intilized contract facotry object with our contract, we can invoke deploy function to deploy the contract.
  //Accepts constructor parameters from our contract
  const greeter = await Greeter.deploy("initial_msg");
  //We use wait to recieve the transaction (deployment) receipt, which contains contractAddress
  const contractAddress = (await greeter.deployTransaction.wait())
    .contractAddress;

  console.log(`Greeter deployed to: ${contractAddress}`);

  return contractAddress;
};

showBalance.js

Returns the balance of the specified wallet address (account) in tinybars. Tinybars are the unit in which Hedera accounts hold HBAR balances.\

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

module.exports = async () => {
  //Assign the first signer, which comes from the first privateKey from our configuration in hardhat.config.js, to a wallet variable.
  const wallet = (await ethers.getSigners())[0];
  //Wallet object (which is essentially signer object) has some built in functionality like getBalance, getAddress and more
  const balance = (await wallet.getBalance()).toString();
  console.log(`The address ${wallet.address} has ${balance} weibars`);

  return balance;
};

test/

The test/ folder contains the test files for the project. The rpc.js file is located in the test folder of the hedera-example-hardhat-project project and references the Hardhat tasks that are defined in the hardhat.config file. When the command npx hardhat test is run, the program executes the rpc.js file.

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

describe("RPC", function () {
  let contractAddress;
  let signers;

  before(async function () {
    signers = await hre.ethers.getSigners();
  });

  it("should be able to get the account balance", async function () {
    const balance = await hre.run("show-balance");
    expect(Number(balance)).to.be.greaterThan(0);
  });

  it("should be able to deploy a contract", async function () {
    contractAddress = await hre.run("deploy-contract");
    expect(contractAddress).to.not.be.null;
  });

  it("should be able to make a contract view call", async function () {
    const res = await hre.run("contract-view-call", { contractAddress });
    expect(res).to.be.equal("initial_msg");
  });

  it("should be able to make a contract call", async function () {
    const msg = "updated_msg";
    await hre.run("contract-call", { contractAddress, msg });
    const res = await hre.run("contract-view-call", { contractAddress });
    expect(res).to.be.equal(msg);
  });
});

.env

A file that stores your environment variables like your accounts, private keys, and references to Hedera network (see previous step).

hardhat.config.js

The Hardhat project configuration file. This file includes information about the Hedera network RPC URLs, accounts, and tasks defined (see previous step).

Test and Deploy

Now that you have your project set up and configured, let's deploy the Greeter.sol smart contract to the Hedera Testnet using Hashio. Hashio is an instance of the Hedera JSON-RPC relay hosted by Swirlds Labs and provides convenient access to the Hedera network for transactions and data querying. You can use any JSON-RPC instance supported by the community.

Run the following command in your terminal to run the hedera-hardhat-example-project/test/rpc.js test file on the Hedera testnet.

npx hardhat test

Tests should pass with "4 passing" returned to the console. Otherwise, an error message will appear indicating the issue.

console check ✅

  RPC
The address 0xe261e26aECcE52b3788Fac9625896FFbc6bb4424 has 99999999999999991611392 weibars
    ✔ should be able to get the account balance (1127ms)
Greeter deployed to: 0xEc3D74D360a53Fe7104Be6aB4e25e27a90bF6aE4
    ✔ should be able to deploy a contract (11810ms)
Contract call result: initial_msg
    ✔ should be able to make a contract view call (265ms)
Updated call result: updated_msg
Contract call result: updated_msg
    ✔ should be able to make a contract call (4068ms)


  4 passing (34s)

Lastly, run the following command to deploy the contract to the Hedera Testnet:

npx hardhat deploy-contract

console check ✅

Greeter deployed to: 0x157B93c04a294AbD88cF608672059814b3ea38aE

You've successfully deployed your contract to the Hedera Testnet! You can view the contract you deployed by searching the smart contract public address in a supported Hedera Network Explorer. For this example, we will use the HashScan Network Explorer. Copy and paste your deployed Greeter.sol public contract address into the HashScan search bar.

The Network Explorer will return the information about the contract created and deployed to the Hedera Testnet. The "EVM Address" field is the public address of the contract that was returned to you in your terminal. The terminal returned the public address with the "0x" hex encoding appended to the public address. You will also notice a contract ID in 0.0.contractNumber (0.0.3478001) format. This is the contract ID used to reference the contract entity in the Hedera Network.

Note: At the top of the explorer page, remember to switch the network to TESTNET before you search for the contract.

Hashscan transaction

Congratulations! 🎉 You have successfully learned how to deploy a smart contract using Hardhat. Feel free to reach out if you have any questions:

Writer: Krystal, Technical Writer

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Editor: Simi, Sr. Software Manager

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