BuyMeACoffee with Hardhat and Solidity

This is a decentralized application (DApp) built with Hardhat and Solidity. It is deployed on the Sepolia testnet and uses Alchemy as its node, as well as the Alchemy API for interacting with the Ethereum network.

Front end code

Prerequisites

To use this project, you will need to install:

• Node.js
• Hardhat

Installation

To install this project:

1. Clone the repository:

git clone https://github.com/your-username/hardhat-solidity-project.git

2. Go to the project directory:

cd hardhat-solidity-project

3. Install the project dependencies:

npm install

Usage

To use this project, you need an Alchemy API key. You can get a key by signing up for a free account at https://alchemyapi.io/.

Once you have your API key, create a file called .env in the root of the project and add the following lines, replacing YOUR_API_KEY with your actual API key and YOUR_GOERLI_URL with the Goerli URL provided by Alchemy and YOUR_PRIVATE_KEY with the private key for your Metamask account:

SEPOLIA_URL=YOUR_SEPOLIA_URL
SEPOLIA_API_KEY=SEPOLIA_API_KEY
PRIVATE_KEY=PRIVATE_KEY

With the API key in place, you can use these Hardhat commands to compile, deploy, and interact with the DApp:

• Compile the Solidity contracts:

npx hardhat compile

• Deploy the contracts to the Goerli testnet:

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

• Run the Hardhat console, which lets you interact with the deployed contracts:

npx hardhat console --network goerli

• Verify the contract:

npx hardhat verify --network goerli <YOUR-CONTRACT-ADDRESS>

Explanation BuyMeACoffee Smart Contract

This smart contract allows users to send ether (ETH) to the contract, along with a name and message. The contract is named BuyMeACoffee and is written in the Solidity programming language for the Ethereum blockchain.

Features

• Emits an event NewMemo when a user buys a coffee, which includes information about the transaction (from address, timestamp, name, and message)

event NewMemo(
    address indexed from,
    uint256 timestamp,
    string name,
    string message
  );

function buyCoffee(
    string memory _name,
    string memory _message
  ) public payable {
    require(msg.value > 0, "Can't buy coffee with 0 eth");

    memos.push(Memo(msg.sender, block.timestamp, _name, _message));

    // Emit a log event when a new memo is created
    emit NewMemo(msg.sender, block.timestamp, _name, _message);
  }

• Stores an array of Memos that are received from users

Memo[] memos;

• Has a variable owner that stores the address of the contract deployer

// Address of contract deployer
  address payable owner;

// Deploy logic
constructor() {
  owner = payable(msg.sender);
  }

• Allows the contract owner to withdraw all the ether that is stored in the contract

function withdrawTips() public {
  require(owner.send(address(this).balance));
}

• Allows anyone to retrieve all the memos stored in the contract.

function getMemos() public view returns (Memo[] memory) {
  return memos;
}

Structs

• Memo:
  • from: address of the user who sent the transaction
  • timestamp: timestamp of the transaction
  • name: name of the user who sent the transaction
  • message: message sent by the user

Functions

buyCoffee

This function allows a user to send ether to the contract and stores their name and message as a Memo in the contract.

Input

• _name: name of the user sending the transaction
• _message: message sent by the user

withdrawTips

This function allows the contract owner to withdraw all the ether that is stored in the contract.

getMemos

This function allows anyone to retrieve all the memos stored in the contract.

Output

• Memo[] : array of memos stored in the contract

Deployment

The address of the contract deployer is assigned to the owner variable upon deployment.

Note

This smart contract is shared under UNLICENSED license. It is intended for educational and informational purposes only, and is not a recommendation or endorsement of any particular smart contract. Use caution when interacting with any smart contract, as they can be complex and potentially unsafe.

The video where i studied

https://www.youtube.com/watch?v=cxxKdJk55Lk&list=PLMj8NvODurfEYLsuiClgikZBGDfhwdcXF&index=2&ab_channel=Alchemy