Constants and immutables in Blockchain / Solidity - Mini Project: Build & Apply

Using Constants and Immutables in Solidity

📖 Scenario: You are creating a simple smart contract for a blockchain-based voting system. You want to set some fixed values that never change after deployment, such as the election name and the maximum number of votes per person.

🎯 Goal: Build a Solidity contract that uses constant and immutable variables to store fixed data and demonstrate how to read them.

📋 What You'll Learn

Create a constant string variable called ELECTION_NAME with the value "Blockchain Election 2024".

Create an immutable unsigned integer variable called maxVotesPerPerson set via the constructor with the value 3.

Write a public function getElectionInfo that returns both ELECTION_NAME and maxVotesPerPerson.

Deploy the contract and print the election info.

💡 Why This Matters

🌍 Real World

Constants and immutables help save gas and ensure important values do not change after deployment in blockchain smart contracts.

💼 Career

Understanding these keywords is essential for blockchain developers to write efficient and secure smart contracts.

1

Create the contract and constant variable

Create a Solidity contract named Voting. Inside it, declare a public constant string variable called ELECTION_NAME and set it to "Blockchain Election 2024".

Blockchain / Solidity

contract Voting {
    // Declare constant election name here
    
}

Need a hint?

Use string public constant ELECTION_NAME = "Blockchain Election 2024"; inside the contract.

2

Add an immutable variable set by constructor

Inside the Voting contract, declare a public immutable uint variable called maxVotesPerPerson. Add a constructor that sets maxVotesPerPerson to 3.

Blockchain / Solidity

contract Voting {
    string public constant ELECTION_NAME = "Blockchain Election 2024";

    // Declare immutable variable
    uint public immutable maxVotesPerPerson;

    // Add constructor to set maxVotesPerPerson to 3
    
}

Need a hint?

Use constructor() { maxVotesPerPerson = 3; } to set the immutable variable.

3

Create a function to return election info

Add a public view function called getElectionInfo that returns (string memory, uint). It should return ELECTION_NAME and maxVotesPerPerson.

Blockchain / Solidity

contract Voting {
    string public constant ELECTION_NAME = "Blockchain Election 2024";

    uint public immutable maxVotesPerPerson;

    constructor() {
        maxVotesPerPerson = 3;
    }

    // Create getElectionInfo function
    function getElectionInfo() public view returns (string memory, uint) {
        // Your code here
    }
}

Need a hint?

Return both variables as a tuple: return (ELECTION_NAME, maxVotesPerPerson);

4

Print the election info

Write a script or test code that calls getElectionInfo and prints the election name and max votes per person in the format: Election: Blockchain Election 2024, Max Votes: 3.

Blockchain / Solidity

contract Voting {
    string public constant ELECTION_NAME = "Blockchain Election 2024";

    uint public immutable maxVotesPerPerson;

    constructor() {
        maxVotesPerPerson = 3;
    }

    function getElectionInfo() public view returns (string memory, uint) {
        return (ELECTION_NAME, maxVotesPerPerson);
    }
}

// Call getElectionInfo and print the result
// Your code here

Need a hint?

Solidity contracts do not print directly. Imagine calling getElectionInfo and displaying the returned values as shown.