First smart contract deployment in Blockchain / Solidity - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is a smart contract?

A smart contract is a small program stored on a blockchain that runs automatically when certain conditions are met. It helps make agreements without needing a middleman.

beginner

What is the first step before deploying a smart contract?

You write the smart contract code, usually in a language like Solidity, and test it locally to make sure it works as expected.

beginner

What tool is commonly used to deploy smart contracts on Ethereum?

Tools like Remix IDE or Truffle are commonly used to compile and deploy smart contracts on Ethereum.

beginner

Why do you need gas to deploy a smart contract?

Gas is the fee paid to the blockchain network to process and store your smart contract. It pays for the computing power used.

beginner

What happens after a smart contract is deployed?

After deployment, the smart contract has its own address on the blockchain. People can interact with it by sending transactions to that address.

What language is commonly used to write smart contracts on Ethereum?

A Solidity

B Python

C JavaScript

D C++

Solidity is the main language designed for writing smart contracts on Ethereum.

What is the purpose of gas in smart contract deployment?

A To pay for the computing resources used

B To store contract code for free

C To speed up the deployment

D To encrypt the contract

Gas is a fee paid to the network to cover the computing power needed to deploy and run contracts.

Which tool can you use to deploy a smart contract directly from your browser?

A Node.js

B Visual Studio Code

C GitHub

D Remix IDE

Remix IDE is a web-based tool that lets you write, compile, and deploy smart contracts easily.

What do you get after successfully deploying a smart contract?

A A private key

B A new cryptocurrency

C A unique blockchain address for the contract

D A software license

The deployed contract lives at a unique address on the blockchain where users can interact with it.

Before deploying, why should you test your smart contract code?

A To increase gas fees

B To avoid costly mistakes on the blockchain

C To make the contract private

D To get a contract address

Testing helps catch errors early so you don’t waste money deploying broken contracts.

Explain the main steps involved in deploying your first smart contract.

Think about what you do from writing code to having a live contract on the blockchain.

Describe why gas fees are important when deploying a smart contract.

Consider what happens behind the scenes when your contract is added to the blockchain.

Practice

1. What does deploying a smart contract mean in blockchain?

easy

A. Testing the contract on a local computer only

B. Making the contract code live and usable on the blockchain

C. Writing the contract code in a text editor

D. Deleting the contract from the blockchain

Solution

1. Step 1: Understand deployment meaning

   Deployment means putting the contract code on the blockchain so it can run.

2. Step 2: Differentiate from writing and testing

   Writing is coding, testing is checking locally or on test networks, deployment is live on blockchain.

3. Final Answer:

   Making the contract code live and usable on the blockchain -> Option B

4. Quick Check:

   Deploy = live on blockchain [OK]

Hint: Deployment means contract is live on blockchain [OK]

Common Mistakes:

• Confusing deployment with just writing code
• Thinking testing is deployment
• Believing deployment deletes contracts

2. Which of the following is the correct Solidity syntax to start a simple contract named MyContract?

easy

A. contract MyContract { }

B. class MyContract { }

C. function MyContract() { }

D. contract = MyContract()

Solution

1. Step 1: Recall Solidity contract declaration

   Solidity uses the keyword contract followed by the contract name and braces.

2. Step 2: Check each option's syntax

   contract MyContract { } matches Solidity syntax; others use wrong keywords or formats.

3. Final Answer:

   contract MyContract { } -> Option A

4. Quick Check:

   Solidity contract starts with 'contract' keyword [OK]

Hint: Solidity contracts start with 'contract' keyword [OK]

Common Mistakes:

• Using 'class' instead of 'contract'
• Writing function instead of contract
• Assigning contract like a variable

3. Given this Solidity contract snippet deployed on a test network:

contract Counter {
  uint count = 0;
  function increment() public {
    count += 1;
  }
  function getCount() public view returns (uint) {
    return count;
  }
}

If you call increment() twice and then getCount(), what is the output?

medium

A. 0

B. 1

C. 2

D. Error: function not found

Solution

1. Step 1: Understand contract state changes

   Each call to increment() adds 1 to count, starting from 0.

2. Step 2: Calculate after two increments

   After two calls, count becomes 2. getCount() returns this value.

3. Final Answer:

   2 -> Option C

4. Quick Check:

   2 increments = count 2 [OK]

Hint: Each increment adds 1; two increments mean count is 2 [OK]

Common Mistakes:

• Forgetting state changes persist on blockchain
• Assuming count resets each call
• Confusing function names

4. You try to deploy this Solidity contract but get a syntax error:

contract Simple {
  uint number
  function setNumber(uint num) public {
    number = num;
  }
}

What is the cause of the error?

medium

A. Missing return type in function

B. Function setNumber must be private

C. Contract name must be lowercase

D. Missing semicolon after uint number

Solution

1. Step 1: Check Solidity syntax rules

   Variable declarations require a semicolon at the end.

2. Step 2: Identify missing semicolon

   uint number line misses a semicolon, causing syntax error.

3. Final Answer:

   Missing semicolon after uint number -> Option D

4. Quick Check:

   Missing semicolon = syntax error [OK]

Hint: Check semicolons after variable declarations [OK]

Common Mistakes:

• Thinking function visibility causes syntax error
• Believing contract names must be lowercase
• Expecting return type for void functions

5. You want to deploy a smart contract that stores user names and their balances. Which approach is best to deploy and test it safely before using real money?

hard

A. Deploy on a test network like Ropsten or Goerli first

B. Deploy directly on the main Ethereum network

C. Write the contract but never deploy it

D. Deploy on a private computer without blockchain

Solution

1. Step 1: Understand deployment environments

   Mainnet uses real money; testnets simulate blockchain without real cost.

2. Step 2: Choose safe testing method

   Deploying on testnets like Ropsten or Goerli lets you test without risking real funds.

3. Final Answer:

   Deploy on a test network like Ropsten or Goerli first -> Option A

4. Quick Check:

   Testnet deployment = safe testing [OK]

Hint: Use test networks to avoid losing real money [OK]

Common Mistakes:

• Deploying directly on mainnet without testing
• Not deploying at all and missing testing
• Using private computer without blockchain for deployment