Hardhat deployment scripts in Blockchain / Solidity - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to import the Hardhat runtime environment.

Blockchain / Solidity

const hre = require('[1]');

Drag options to blanks, or click blank then click option'

Aethers

Bhardhat

Cweb3

Dtruffle

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'ethers' instead of 'hardhat' to import hre.

Trying to import 'web3' which is a different library.

The Hardhat runtime environment is imported using require('hardhat').

2fill in blank

medium

Complete the code to get the contract factory for deployment.

Blockchain / Solidity

const Contract = await hre.ethers.getContract[1]('MyContract');

Drag options to blanks, or click blank then click option'

AInstance

BProvider

CSigner

DFactory

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'getContractInstance' which does not exist.

Using 'getContractSigner' which is unrelated.

To deploy a contract, you get its factory using getContractFactory.

3fill in blank

hard

Fix the error in the deployment code to wait for the contract to be deployed.

Blockchain / Solidity

const contract = await Contract.deploy();
await contract.[1]();

Drag options to blanks, or click blank then click option'

AdeployTransaction

Bdeploy

Cdeployed

Dwait

Attempts:

3 left

💡 Hint

Common Mistakes

Calling 'deploy()' again instead of 'deployed()'.

Using 'wait()' which is not a method on the contract instance.

After calling deploy(), you wait for deployment with deployed().

4fill in blank

hard

Fill both blanks to log the deployed contract address and exit the script.

Blockchain / Solidity

console.log('Contract deployed to:', contract.[1]);
process.[2](0);

Drag options to blanks, or click blank then click option'

Aaddress

Bexit

Cdeployed

Dstop

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'deployed' instead of 'address' for the contract property.

Using 'stop' instead of 'exit' to end the process.

The deployed contract address is accessed with address. To end the script, use process.exit(0).

5fill in blank

hard

Fill all three blanks to handle errors and run the main deployment function.

Blockchain / Solidity

async function main() {
  // deployment code
}

main()
  .[1](() => process.exit(0))
  .[2]((error) => {
    console.error(error);
    process.[3](1);
  });

Drag options to blanks, or click blank then click option'

Athen

Bcatch

Cexit

Dfinally

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'finally' instead of 'catch' for error handling.

Using 'stop' instead of 'exit' to end the process.

Promises use then for success and catch for errors. To exit with error code, use process.exit(1).

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