Using Hardhat

Hardhat is a comprehensive Ethereum development tool that simplifies the process of deploying, testing, and debugging smart contracts. It's designed to offer developers a seamless experience when working with Solidity contracts.

Prerequisites

Software

Node v18+, can be downloaded Here

Getting Started with Hardhat. More Information. These directions demonstrate using npm commands to create a project and add its dependencies.

mkdir hardhat-example
cd hardhat-example
npm init
npm install --save-dev hardhat
npx hardhat init

Fund Your Wallet

Navigate to the Crescendo Previewnet Faucet. Paste in your wallet address to get receive $FLOW. This will allow your wallet address to deploy smart contracts.

Deploying a Smart Contract using Hardhat

This section is dedicated to guiding you through deploying smart contracts on the Flow EVM network using Hardhat.

Configuration

Make sure to add FlowEVM network to hardhat.config.ts

require('dotenv').config()
import "@nomiclabs/hardhat-ethers";
import { HardhatUserConfig } from "hardhat/config";
const config: HardhatUserConfig = {
 solidity: "0.8.19",
 networks: {
    previewNet: {
            url: "https://previewnet.evm.nodes.onflow.org",
            accounts: [`<PRIVATE_KEY>`],
            gas: 500000, // Example gas limit
        }
    }
};
export default config;

To keep this example straightforward, we've included the account's private key directly in hardhat.config.ts. However, it is crucial to avoid committing private keys to your Git repository for security reasons. Instead, opt for using environment variables for safer handling of sensitive information.

Deploying HelloWorld Smart Contract

HelloWorld Smart Contract

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.0;
contract HelloWorld {
    // Declare a public field of type string.
    string public greeting;
    // Constructor to initialize the greeting.
    // In Solidity, the constructor is defined with the "constructor" keyword.
    constructor() {
        greeting = "Hello, World!";
    }
    // Public function to change the greeting.
    // The "public" keyword makes the function accessible from outside the contract.
    function changeGreeting(string memory newGreeting) public {
        greeting = newGreeting;
    }
    // Public function that returns the greeting.
    // In Solidity, explicit return types are declared.
    function hello() public view returns (string memory) {
        return greeting;
    }
}

Deploying:

Create a file named HelloWorld.sol under contracts directory.
Add above HelloWorld.sol contract code to new file.
Create a deploy.ts file in scripts directory.
Paste in the following TypeScript code.

import { ethers } from "hardhat";
async function main() {
    const HelloWorld = await ethers.getContractFactory("HelloWorld");
    console.log("Deploying HelloWorld...")
    const helloWorld = await HelloWorld.deploy();
    console.log("HelloWorld address:", helloWorld.address);
}
main()
    .then(() => process.exit(0))
    .catch((error) => {
        console.error(error);
        process.exit(1);
    });

Run npx hardhat run scripts/deploy.ts --network previewNet in the project root.
Get the deployed contract address. This address will be used in other scripts.

Output should look like this:

❯ npx hardhat run scripts/deploy.ts --network previewNet
Deploying HelloWorld...
HelloWorld address: 0x3Fe94f43Fb5CdB8268A801f274521a07F7b99dfb

Get HelloWorld contract Greeting

Get the Greeting from the deployed HelloWorld smart contract.

import { ethers } from "hardhat";
import HelloWorldABI from "../contracts/HelloWorldABI.json"
async function main() {
    // Replace with your contract's address
    const contractAddress = "0x3Fe94f43Fb5CdB8268A801f274521a07F7b99dfb";
    // Get hardhat provider
    const provider = ethers.provider;
    // Create a new contract instance
    const helloWorldContract = new ethers.Contract(contractAddress, HelloWorldABI, provider);
    // Call the greeting function
    const greeting = await helloWorldContract.hello();
    console.log("The greeting is:", greeting);
}
main().catch((error) => {
    console.error(error);
    process.exit(1);
});

Steps:

Create new file getGreeting.ts in scripts directory.
Paste contents of script above. Make sure to update the contract address with the one from deployment in earlier step.
Call script to get HelloWorld greeting, npx hardhat run scripts/getGreeting.ts --network previewNet
The output should be as follows:

❯ npx hardhat run scripts/getGreeting.ts --network previewNet
The greeting is: Hello, World!

Update Greeting on HelloWorld Smart Contract

import HelloWorldABI from "../contracts/HelloWorldABI.json"
import { ethers } from "hardhat";
async function main() {
    const contractAddress = "0x3Fe94f43Fb5CdB8268A801f274521a07F7b99dfb";
    const newGreeting = process.env.NEW_GREETING;
    if (!newGreeting) {
        console.error("Please set the NEW_GREETING environment variable.");
        process.exit(1);
    }
    // Signer to send the transaction (e.g., the first account from the hardhat node)
    const [signer] = await ethers.getSigners();
    // Contract instance with signer
    const helloWorldContract = new ethers.Contract(contractAddress, HelloWorldABI, signer);
    console.log("The greeting is:", await helloWorldContract.hello());
    // Create and send the transaction
    const tx = await helloWorldContract.changeGreeting(newGreeting);
    console.log("Transaction hash:", tx.hash);
    // Wait for the transaction to be mined
    await tx.wait().catch((error: Error) => {});
    console.log("Greeting updated successfully!");
    console.log("The greeting is:", await helloWorldContract.hello());
}
main().catch((error) => {
    console.error(error);
    process.exit(1);
});

Next we'll add a script to update the greeting and log it. Here are the steps to follow:

Create new script updateGreeting.ts file in the scripts directory
Paste in the TypeScript above, Make sure to update the contract address with the one from deployment in earlier step.
Call the new script, NEW_GREETING='Howdy!' npx hardhat run ./scripts/updateGreeting.ts --network previewNet
Output should be

❯ NEW_GREETING='Howdy!' npx hardhat run ./scripts/updateGreeting.ts --network previewNet
The greeting is: Hello, World!
Transaction hash: 0x03136298875d405e0814f54308390e73246e4e8b4502022c657f04f3985e0906
Greeting updated successfully!
The greeting is: Howdy!

Flow EVM Block explorer

Coming Soon

info

Coming Soon

Comprehensive Guides: Step-by-step tutorials on deploying various types of smart contracts, including NFTs (ERC-721), using Hardhat on the FlowEVM network.
Requirements: Detailed prerequisites for using Hardhat with FlowEVM, including Node.js setup, wallet preparation, and obtaining testnet FLOW for gas fees.
Verification and Interaction: Steps to verify your smart contracts on FlowEVM and interact with them using tools like Flowdiver.

Stay tuned for updates and feel free to check back soon for the full guide.

Using Hardhat

Prerequisites​

Software​

Fund Your Wallet​

Deploying a Smart Contract using Hardhat​

Configuration​

Deploying HelloWorld Smart Contract​

HelloWorld Smart Contract​

Get HelloWorld contract Greeting​

Update Greeting on HelloWorld Smart Contract​

Flow EVM Block explorer​

Coming Soon​

Coming Soon​

Prerequisites

Software

Fund Your Wallet

Deploying a Smart Contract using Hardhat

Configuration

Deploying HelloWorld Smart Contract

HelloWorld Smart Contract

Get HelloWorld contract Greeting

Update Greeting on HelloWorld Smart Contract

Flow EVM Block explorer

Coming Soon

Coming Soon