Return values in Blockchain / Solidity - Mini Project: Build & Apply

Return Values in Blockchain Smart Contracts

📖 Scenario: You are creating a simple blockchain smart contract to store and retrieve a user's favorite number. This contract will help users save their number and get it back when needed.

🎯 Goal: Build a smart contract that stores a number and returns it when requested using a function with a return value.

📋 What You'll Learn

Create a state variable to store a number

Create a function to set the number

Create a function to get the stored number with a return value

Print the returned number in the final step

💡 Why This Matters

🌍 Real World

Smart contracts often store data and return values to users or other contracts. Understanding return values is key to building interactive blockchain applications.

💼 Career

Blockchain developers must write functions that return data correctly to enable decentralized apps to work smoothly and securely.

1

Create a state variable to store a number

Create a public state variable called favoriteNumber of type uint to store the user's favorite number.

Blockchain / Solidity

pragma solidity ^0.8.0;

contract FavoriteNumber {
    // Your code here
}

Need a hint?

Use uint public favoriteNumber; inside the contract to create the variable.

2

Create a function to set the number

Add a public function called setNumber that takes a uint parameter named _number and sets favoriteNumber to this value.

Blockchain / Solidity

pragma solidity ^0.8.0;

contract FavoriteNumber {
    uint public favoriteNumber;

    // Your code here
}

Need a hint?

Define function setNumber(uint _number) public and assign favoriteNumber = _number;.

3

Create a function to get the stored number with a return value

Add a public view function called getNumber that returns a uint and returns the value of favoriteNumber.

Blockchain / Solidity

pragma solidity ^0.8.0;

contract FavoriteNumber {
    uint public favoriteNumber;

    function setNumber(uint _number) public {
        favoriteNumber = _number;
    }

    // Your code here
}

Need a hint?

Use function getNumber() public view returns (uint) and return favoriteNumber.

4

Print the returned number

Write a script to create the contract, call setNumber(42), then call getNumber() and print the returned value.

Blockchain / Solidity

// This step requires a script outside Solidity to interact with the contract
// Your code here

Need a hint?

Use a script to call setNumber(42) then getNumber() and print the result.