Hardhat deployment scripts in Blockchain / Solidity - Mini Project: Build & Apply

Hardhat Deployment Scripts

📖 Scenario: You are building a simple Ethereum smart contract deployment project using Hardhat. Hardhat is a tool that helps developers deploy smart contracts to Ethereum networks easily.In this project, you will create a deployment script step-by-step to deploy a basic smart contract called SimpleStorage that stores a number.

🎯 Goal: Build a Hardhat deployment script that deploys the SimpleStorage contract to a local Ethereum network.

📋 What You'll Learn

Create a deployment script file named deploy.js inside the scripts folder.

Use Hardhat Runtime Environment (hre) to deploy the contract.

Deploy the SimpleStorage contract and wait for deployment to finish.

Print the deployed contract address to the console.

💡 Why This Matters

🌍 Real World

Deploying smart contracts is a key step in launching blockchain applications like tokens, games, or finance apps.

💼 Career

Blockchain developers must write deployment scripts to automate contract deployment and testing in professional projects.

1

Create the deployment script file and import Hardhat

Create a file named deploy.js inside the scripts folder. Inside it, write const hre = require("hardhat"); to import Hardhat Runtime Environment.

Blockchain / Solidity

const hre = require("hardhat");
// Your code here

Hint

Use require("hardhat") to import Hardhat Runtime Environment as hre.

2

Write an async function to deploy the SimpleStorage contract

Write an async function named main. Inside it, get the contract factory for SimpleStorage using hre.ethers.getContractFactory("SimpleStorage") and store it in a variable called SimpleStorage. Then deploy the contract by calling SimpleStorage.deploy() and store the deployed contract in a variable called simpleStorage. Use await to wait for deployment to finish by calling simpleStorage.deployed().

Blockchain / Solidity

const hre = require("hardhat");

async function main() {
    // Your code here
}

Hint

Use hre.ethers.getContractFactory to get the contract factory, then deploy and wait for deployment.

3

Call the main function and handle errors

After the main function, call it and add .then(() => process.exit(0)) to exit successfully. Add .catch((error) => { console.error(error); process.exit(1); }) to catch and print errors and exit with failure.

Blockchain / Solidity

const hre = require("hardhat");

async function main() {
    const SimpleStorage = await hre.ethers.getContractFactory("SimpleStorage");
    const simpleStorage = await SimpleStorage.deploy();
    await simpleStorage.deployed();
}

// Your code here

Hint

Use main().then(...).catch(...) to run the async function and handle errors.

4

Print the deployed contract address

Inside the main function, after await simpleStorage.deployed(), add a console.log statement to print "SimpleStorage deployed to:" followed by simpleStorage.address.

Blockchain / Solidity

const hre = require("hardhat");

async function main() {
    const SimpleStorage = await hre.ethers.getContractFactory("SimpleStorage");
    const simpleStorage = await SimpleStorage.deploy();
    await simpleStorage.deployed();
    // Your code here
}

main()
    .then(() => process.exit(0))
    .catch((error) => {
        console.error(error);
        process.exit(1);
    });

Hint

Use console.log("SimpleStorage deployed to:", simpleStorage.address) to print the address.

Practice

1. What is the main purpose of a Hardhat deployment script?

easy

A. To test smart contracts locally

B. To write smart contract logic

C. To automate deploying smart contracts to the blockchain

D. To create user interfaces for contracts

Solution

1. Step 1: Understand deployment scripts

   Deployment scripts are used to automate the process of putting smart contracts on the blockchain.

2. Step 2: Differentiate from other tasks

   Writing contract logic, testing, and UI creation are separate tasks from deployment.

3. Final Answer:

   To automate deploying smart contracts to the blockchain -> Option C

4. Quick Check:

   Deployment script = automate deployment [OK]

Hint: Deployment scripts automate contract deployment fast [OK]

Common Mistakes:

• Confusing deployment with contract coding
• Thinking deployment scripts test contracts
• Assuming deployment scripts build UI

2. Which of the following is the correct way to get a contract factory in a Hardhat deployment script?

easy

A. const Contract = await ethers.getContractFactory('MyContract');

B. const Contract = ethers.getContract('MyContract');

C. const Contract = await ethers.deployContract('MyContract');

D. const Contract = ethers.createContractFactory('MyContract');

Solution

1. Step 1: Recall ethers.js method

   The correct method to prepare a contract for deployment is ethers.getContractFactory with await.

2. Step 2: Check syntax correctness

   Options B, C, and D use incorrect method names or miss await keyword.

3. Final Answer:

   const Contract = await ethers.getContractFactory('MyContract'); -> Option A

4. Quick Check:

   Use getContractFactory with await [OK]

Hint: Use await ethers.getContractFactory('Name') to prepare contract [OK]

Common Mistakes:

• Omitting await before getContractFactory
• Using wrong method names like getContract or deployContract
• Confusing contract factory with contract instance

3. Consider this Hardhat deployment script snippet:

const Token = await ethers.getContractFactory('Token');
const token = await Token.deploy();
await token.deployed();

const Sale = await ethers.getContractFactory('Sale');
const sale = await Sale.deploy(token.address);
await sale.deployed();

console.log(sale.address);

What will be printed by console.log(sale.address)?

medium

A. The deployed address of the Token contract

B. An error because token.address cannot be passed

C. Undefined, because sale.address is not set

D. The deployed address of the Sale contract

Solution

1. Step 1: Understand deployment sequence

   The Token contract is deployed first, then its address is passed to Sale contract deployment.

2. Step 2: Identify sale.address value

   After deployment, sale.address holds the Sale contract's blockchain address, which is logged.

3. Final Answer:

   The deployed address of the Sale contract -> Option D

4. Quick Check:

   sale.address = Sale contract address [OK]

Hint: Deployed contract instance has .address property [OK]

Common Mistakes:

• Confusing token.address with sale.address
• Assuming sale.address is undefined before deployment
• Thinking passing token.address causes error

4. Identify the error in this Hardhat deployment script snippet:

const Token = ethers.getContractFactory('Token');
const token = await Token.deploy();
await token.deployed();

medium

A. Missing await before ethers.getContractFactory

B. Missing await before Token.deploy()

C. Missing await before token.deployed()

D. No error, the code is correct

Solution

1. Step 1: Check getContractFactory usage

   ethers.getContractFactory returns a promise, so it needs await.

2. Step 2: Verify other awaits

   Token.deploy() and token.deployed() correctly use await.

3. Final Answer:

   Missing await before ethers.getContractFactory -> Option A

4. Quick Check:

   Always await getContractFactory [OK]

Hint: Always await getContractFactory call [OK]

Common Mistakes:

• Forgetting await on getContractFactory
• Confusing which calls need await
• Assuming deploy() is synchronous

5. You want to deploy two contracts, Token and Marketplace, where Marketplace needs the Token address in its constructor. Which is the correct way to write the deployment script?

hard

A. Deploy Marketplace first, then deploy Token passing marketplace.address

B. Deploy Token first, then deploy Marketplace passing token.address

C. Deploy both contracts simultaneously without passing addresses

D. Deploy Token and Marketplace separately without constructor arguments

Solution

1. Step 1: Understand constructor dependency

   Marketplace requires Token's address, so Token must be deployed first to get its address.

2. Step 2: Deploy in correct order

   Deploy Token, then deploy Marketplace passing token.address to its constructor.

3. Step 3: Reject incorrect options

   Deploying Marketplace first or simultaneously won't provide Token's address; omitting constructor args breaks dependency.

4. Final Answer:

   Deploy Token first, then deploy Marketplace passing token.address -> Option B

5. Quick Check:

   Deploy dependencies first, then dependent contracts [OK]

Hint: Deploy dependencies first, pass addresses to dependent contracts [OK]

Common Mistakes:

• Deploying dependent contract before dependency
• Not passing required constructor arguments
• Deploying contracts simultaneously ignoring dependencies