Day 4 / 100DaysOfWeb3

For today's challenge I will be using the Ropsten test network using a Metamask, Solidity, Hardhat and Alchemy virtual wallet.

I use this tutorial on Web 3 University website.

Step 1 : I created Alchemy account and created a new app named Hello world.

Step 2 : I created an Ethereum account and add ether from a Faucet through this link Ropsten faucet and check my account balance using Alchemy's composer tool

Step 3 : Create and Deploy project

• Initialize my project in a working directory with

npm init

• Add Hardhat to the project with

npm install --save-dev hardhat

• Create hardhat project

npx hardhat

• Add contracts and scripts directory to the project

• I write my contract with this code

// Specifies the version of Solidity, using semantic versioning.
// Learn more: https://solidity.readthedocs.io/en/v0.5.10/layout-of-source-files.html#pragma
pragma solidity >=0.7.3;

// Defines a contract named `HelloWorld`.
// A contract is a collection of functions and data (its state). Once deployed, a contract resides at a specific address on the Ethereum blockchain. Learn more: https://solidity.readthedocs.io/en/v0.5.10/structure-of-a-contract.html
contract HelloWorld {

   //Emitted when update function is called
   //Smart contract events are a way for your contract to communicate that something happened on the blockchain to your app front-end, which can be 'listening' for certain events and take action when they happen.
   event UpdatedMessages(string oldStr, string newStr);

   // Declares a state variable `message` of type `string`.
   // State variables are variables whose values are permanently stored in contract storage. The keyword `public` makes variables accessible from outside a contract and creates a function that other contracts or clients can call to access the value.
   string public message;

   // Similar to many class-based object-oriented languages, a constructor is a special function that is only executed upon contract creation.
   // Constructors are used to initialize the contract's data. Learn more:https://solidity.readthedocs.io/en/v0.5.10/contracts.html#constructors
   constructor(string memory initMessage) {

      // Accepts a string argument `initMessage` and sets the value into the contract's `message` storage variable).
      message = initMessage;
   }

   // A public function that accepts a string argument and updates the `message` storage variable.
   function update(string memory newMessage) public {
      string memory oldMsg = message;
      message = newMessage;
      emit UpdatedMessages(oldMsg, newMessage);
   }
}

Step 4 : I connect MetaMask and Alchemy to my project by creating a dotenv file with these params

API_URL = "https://eth-ropsten.alchemyapi.io/v2/your-api-key"
PRIVATE_KEY = "your-metamask-private-key"

Step 5 : I Installed Ether.js with this code

npm install --save-dev @nomiclabs/hardhat-ethers "ethers@^5.0.0"

Then update hardhat.config.js to this :

/**
* @type import('hardhat/config').HardhatUserConfig
*/

require('dotenv').config();
require("@nomiclabs/hardhat-ethers");

const { API_URL, PRIVATE_KEY } = process.env;

module.exports = {
   solidity: "0.7.3",
   defaultNetwork: "ropsten",
   networks: {
      hardhat: {},
      ropsten: {
         url: API_URL,
         accounts: [`0x${PRIVATE_KEY}`]
      }
   },
}

I compiled my contract with

npx hardhat compile

After compiled it, I create a deploy.js file in scripts folder

async function main() {
   const HelloWorld = await ethers.getContractFactory("HelloWorld");

   // Start deployment, returning a promise that resolves to a contract object
   const hello_world = await HelloWorld.deploy("Hello World!");
   console.log("Contract deployed to address:", hello_world.address);
}

main()
  .then(() => process.exit(0))
  .catch(error => {
    console.error(error);
    process.exit(1);
  });

Step 6 : Deploy my contract

To deploy my contract, I run this command :

npx hardhat run scripts/deploy.js --network ropsten

• My Contract is deployed to address: 0x1309BF30314A252DF4bfC0BEb819E4def6407270