Web3 Basics with Solidity

Hey there, football fans! If you’re interested in building Decentralized Applications (dApps) on the Ethereum blockchain, then you’ll want to learn about Solidity and web3.js.

Solidity

First off, let’s define what Solidity is.

Solidity is a programming language used to write smart contracts on the Ethereum blockchain.

Smart contracts are self-executing contracts that can be used to automate the exchange of assets, such as cryptocurrencies or digital assets like NFTs.

Web3

Web3.js is a JavaScript library used to interact with the Ethereum blockchain.

It provides a set of tools and functions that allow developers to build dApps and interact with smart contracts.

So, how can you use Solidity along with web3.js?

Imagine you’re a Liverpool fan and you want to create a dApp that allows fans to vote on the club’s player of the month.

You could create a smart contract in Solidity that stores the votes and use web3.js to interact with the contract.

Here’s an example of what the Solidity smart contract could look like:

pragma solidity ^0.8.0;

contract PlayerOfTheMonth {

    // Map to keep track of votes received for each address
    mapping(address => uint256) public votes;

    // Array to keep track of all voters' addresses
    address[] public voters;

    // Address of the owner of the contract
    address public owner;

    // Constructor to initialize owner variable
    constructor() {
        owner = msg.sender;
    }

    // Function to allow anyone except the owner to vote for Player of the Month
    function vote() public {

        // Require that the sender is not the owner of the contract
        require(msg.sender != owner, "Owner cannot vote");

        // Require that the sender has not already voted
        require(votes[msg.sender] == 0, "Already voted");

        // Add sender's address to voters array and set their vote count to the current number of voters
        votes[msg.sender] = voters.length + 1;
        voters.push(msg.sender);
    }

    // Function to get the address of the winner of the vote
    function getWinner() public view returns (address) {

        // Require that there have been votes cast
        require(voters.length > 0, "No votes");

        // Index of the current winner, initially set to the first address in the voters array
        uint256 winnerIndex = 0;

        // Loop through all voters' addresses and compare their vote counts to the current winner's
        for (uint256 i = 1; i < voters.length; i++) {
            if (votes[voters[i]] > votes[voters[winnerIndex]]) {
                winnerIndex = i;
            }
        }

        // Return the address of the winner
        return voters[winnerIndex];
    }
}

In this example, we’re creating a smart contract called PlayerOfTheMonth that stores the votes for each fan who votes.

We’re also storing the addresses of the voters in an array.

The contract owner cannot vote, and each fan can only vote once.

To interact with the contract using web3.js, you would need to first connect to an Ethereum node using the Web3() constructor.

Here’s an example of what that would look like:

// Import the Web3 library
const Web3 = require('web3');

// Create a new instance of Web3, connecting to the Ethereum mainnet using Infura
const web3 = new Web3('https://mainnet.infura.io/v3/your-project-id');

// Specify the contract address and ABI
const contractAddress = '0x123...';
const contractABI = [...];

// Create a new contract instance using the address and ABI
const contract = new web3.eth.Contract(contractABI, contractAddress);

// Call the vote function on the contract and send the transaction from a specific Ethereum address
contract.methods.vote().send({ from: '0x456...' });

In this example, we’re connecting to the Ethereum mainnet using Infura as the node provider.

We’re also specifying the contract address and ABI, which is the interface for interacting with the contract.

Finally, we’re calling the vote() function on the contract and sending the transaction from a specific address.

Once the voting period is over, you could call the getWinner() function to determine the winner of the player of the month award.

Conclusion

In conclusion, Solidity and web3.js are powerful tools for building dApps on the Ethereum blockchain.

It provide an opportunity to create unique applications that engage in a new and exciting ways.

So, whether you’re a football fan or not, consider exploring the world of Solidity and Web3

Peace out!