Deploy a Contract with Hardhat

Overview

Hardhat is one of the popular smart contract development frameworks. It is the Merlin’s preferred framework, and therefore used in the Merlin as a default for deploying and automatically verifying smart contracts.

Prerequisites

Before you begin, you will need to prepare the following:

• Prepare one EVM account。

• Send some BTC to the account as gas fee 。 You can first bridge some BTC via Merlin Bridge (https://merlinchain.io/bridge) and send the BTC to your EVM account used to deploy contracts.

Initialize Hardhat project

• mkdir <project-name>;cd <project-name>

• Initialize a project with Hardhat: npx hardhat.

• Next, (… To avoid failure … please go slow with this cli dialogue…)

• Press <ENTER> to set the project root.

• Press <ENTER> again to accept addition of .gitignore.

• Type n to reject installing sample project's dependencies.

  The idea here is to postpone installing dependencies to later steps due to a possible version-related bug.

Configure Hardhat project

Open the hardhat.config.js file and paste the below code:

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

/** @type import('hardhat/config').HardhatUserConfig */
module.exports = {
solidity: "0.8.9",
paths: {
    artifacts: "./src",
},
networks: {
    merlinTestnet: {
    url: `https://testnet-rpc.merlinchain.io`,
    accounts: [process.env.ACCOUNT_PRIVATE_KEY],
    },
},
};

Add smart contract

• Create a new file, in the contracts folder, named Counter.sol: touch contracts/Counter.sol.

• Copy the below code and paste it in the Counter contract code:

  //SPDX-License-Identifier: MIT
  pragma solidity ^0.8.9;
  
  contract Counter {
  uint256 currentCount = 0;
  
      function increment() public {
          currentCount = currentCount + 1;
      }
  
      function retrieve() public view returns (uint256){
          return currentCount;
      }
  }

Add deploy script

• Create a new file in the scripts folder deploy-counter.js: touch scripts/deploy-counter.js.

• Add the code below to the deploy-counter.js file:

  const hre = require("hardhat");
  
  async function main() {
      const deployedContract = await hre.ethers.deployContract("Counter");
      await deployedContract.waitForDeployment();
      console.log(
          `Counter contract deployed to https://testnet-scan.merlinchain.io/address/${deployedContract.target}`
      );
  }
  
  main().catch((error) => {
      console.error(error);
      process.exitCode = 1;
  });

Compile and deploy

• Before compiling the contract, you need to install the toolbox. You may need to change directory to install outside the project. Use this command:

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

• Compile your contract code (i.e., go back to the project root in the CLI):

  npx hardhat compile

• Now run the scripts:

  npx hardhat run scripts/deploy-counter.js --network merlinTestnet

  ​Here’s an output example:

  Counter contract deployed tohttps://testnet-scan.merlinchain.io/address/0x5bB1814A9226eFB912d439fdBcB59ce802aDCBB8