Hardhat deployment scripts in Blockchain / Solidity - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is the main purpose of a Hardhat deployment script?

A Hardhat deployment script automates the process of deploying smart contracts to a blockchain network, making it easier and repeatable.

beginner

In a Hardhat deployment script, what does the function hre.ethers.getContractFactory do?

It creates a contract factory object that allows you to deploy new instances of a smart contract.

beginner

Why do we use await when deploying contracts in Hardhat scripts?

Because deploying contracts is an asynchronous operation that takes time, await ensures the script waits for deployment to finish before moving on.

intermediate

What is the role of the main function in a Hardhat deployment script?

The main function contains the deployment logic and is executed to deploy contracts. It is usually wrapped in a try-catch block to handle errors.

intermediate

How can you pass constructor arguments to a contract during deployment in a Hardhat script?

You pass constructor arguments as parameters to the deploy method of the contract factory, e.g., Contract.deploy(arg1, arg2).

What does hre stand for in Hardhat deployment scripts?

A Hardhat Runtime Environment

B Hardhat Remote Execution

C Hardhat Resource Engine

D Hardhat React Extension

hre is the Hardhat Runtime Environment, which provides access to Hardhat's functionalities in scripts.

Which keyword is used to wait for a contract deployment to complete in a Hardhat script?

A await

B defer

C wait

D pause

await pauses the script until the asynchronous deployment finishes.

How do you handle errors in a Hardhat deployment script?

A Using <code>if-else</code> statements

B Using <code>try-catch</code> blocks

C Using <code>switch-case</code>

D No error handling is needed

try-catch blocks catch errors during deployment and allow graceful handling.

What command runs a Hardhat deployment script?

A hardhat deploy

B npm start <script>

C npx hardhat run <script>

D node deploy.js

The command npx hardhat run executes deployment scripts using Hardhat.

Where do you usually specify the network to deploy to in Hardhat?

A In the deployment script

B In the package.json file

C In the smart contract code

D In the Hardhat config file

The network is configured in the Hardhat config file, which the deployment script uses.

Explain the steps to write a basic Hardhat deployment script for a smart contract.

Think about how you prepare, deploy, and handle errors in the script.

Describe how constructor arguments are passed during contract deployment in Hardhat scripts.

Focus on the deploy method call and its parameters.

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