Constructor function in Blockchain / Solidity - Mini Project: Build & Apply

Constructor Function in a Blockchain Smart Contract

📖 Scenario: You are creating a simple blockchain smart contract to store and manage a greeting message. This contract will have a constructor function that sets the initial greeting when the contract is deployed.

🎯 Goal: Build a smart contract with a constructor function that initializes a greeting message. Then, display the greeting message stored in the contract.

📋 What You'll Learn

Create a contract named GreetingContract

Add a public string variable called greeting

Write a constructor function that takes a string parameter called _greeting and sets the greeting variable

Add a function called getGreeting that returns the current greeting

Print the greeting message by calling getGreeting

💡 Why This Matters

🌍 Real World

Smart contracts on blockchains often need constructor functions to set initial data like owner addresses or configuration settings when deployed.

💼 Career

Understanding constructor functions is essential for blockchain developers to create secure and functional smart contracts.

1

Create the contract and greeting variable

Create a contract named GreetingContract and inside it, declare a public string variable called greeting.

Blockchain / Solidity

contract GreetingContract {
    // Declare a public string variable greeting
    // Your code here
}

Need a hint?

Use contract GreetingContract {} to start the contract and declare string public greeting; inside.

2

Add the constructor function

Add a constructor function inside GreetingContract that takes a string parameter called _greeting and sets the greeting variable to _greeting.

Blockchain / Solidity

contract GreetingContract {
    string public greeting;

    // Add constructor function here
    // Your code here
}

Need a hint?

Use constructor(string memory _greeting) { greeting = _greeting; } inside the contract.

3

Add a function to get the greeting

Add a public view function called getGreeting that returns the string greeting.

Blockchain / Solidity

contract GreetingContract {
    string public greeting;

    constructor(string memory _greeting) {
        greeting = _greeting;
    }

    // Add getGreeting function here
    // Your code here
}

Need a hint?

Define function getGreeting() public view returns (string memory) { return greeting; }.

4

Display the greeting message

Write a comment showing how to call getGreeting to display the greeting message stored in the contract.

Blockchain / Solidity

contract GreetingContract {
    string public greeting;

    constructor(string memory _greeting) {
        greeting = _greeting;
    }

    function getGreeting() public view returns (string memory) {
        return greeting;
    }
}

// Your code here to show how to get the greeting

Need a hint?

Write a comment like // Call getGreeting() to display the greeting message stored in the contract.