8.1 Writing the Contract

This Solidity contract, called FreCxPayment, is a simple payment receiver that allows anyone to send cryptocurrency to it and keeps track of the total balance. The pay() function is marked as payable, meaning users can send funds when calling it, and it ensures that some amount is sent using a require check; once successful, it logs the transaction using an event (PaymentReceived) that records the sender and amount for transparency on the blockchain. The contract also includes a getBalance() function, which lets anyone view the total funds stored in the contract by returning its balance, but importantly, it does not include any way to withdraw or manage those funds, making it a basic one-way payment collection contract.

Create a new file and paste:

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.0;

contract FreCxPayment {

    event PaymentReceived(address sender, uint amount);

    function pay() public payable {
        require(msg.value > 0, "Send some FreCx");
        emit PaymentReceived(msg.sender, msg.value);
    }

    function getBalance() public view returns (uint) {
        return address(this).balance;
    }
}