previousOwner

newOwner

OwnershipTransferred

owner

renounceOwnership

requestEth

requests

_amount

setTransferEthAmount

transferEthAmount

transferOwnership

withdraw

pragma solidity ^0.8.0;

import "@openzeppelin/contracts/access/Ownable.sol";

/**
 * @title EvmFaucet
 * @dev A faucet contract that allows users to request a small amount of ETH
 * @dev Users can request ETH once every 24 hours
 * @dev The contract has a balance that can be funded by the owner
 * @dev The owner can also change the amount of ETH given on each request
 */
contract EvmFaucet is Ownable {
    mapping(address => uint256) public requests;
    uint256 public transferEthAmount;

    /**
     * @dev constructor to set the default value of transferEthAmount
     */
    constructor() {
        transferEthAmount = 10000000000000000; // 0.01 ETH in wei
    }

    /**
     * @dev function to request a small amount of ETH
     * @dev The function checks if the contract has enough balance
     * @dev The function also checks if the user has requested before
     * @dev If all the conditions are met, the function will transfer the amount stored in transferEthAmount to the user address
     * @param _to address to send the eth
     */
    function requestEth(address _to) public {
        require(address(this).balance >= transferEthAmount, "The contract balance is insufficient");
        require(_to != address(0), "Request not allowed from address 0x0");
        require(block.timestamp - requests[_to] >= 86400, "You must wait 24 hours to request again"); // 24 hours in seconds
        payable(_to).transfer(transferEthAmount);
        requests[_to] = block.timestamp;
    }

    /**
     * @dev receive function to receive ETH to fund the contract
     * @dev the function checks that the value received is greater than zero, otherwise it will throw an error message
     */
    receive() payable external {
        require(msg.value > 0, "You must send a positive value");
    }
    
    /**
     * @dev function that allows the owner to withdraw the contract balance
     * @dev the function checks that the contract has a balance greater than zero
     * @dev The function will be executed only by the owner of the contract
     */
    function withdraw() public onlyOwner {
        require(address(this).balance > 0, "The contract balance is zero");
        payable(msg.sender).transfer(address(this).balance);
    }

    /**
     * @dev function that allows the owner to change the value of the transferEthAmount
     * @param _amount new amount that should be equal or greater than zero
     * @dev The function will be executed only by the owner of the contract
     */
    function setTransferEthAmount(uint256 _amount) public onlyOwner {
        require(_amount >= 0, "The amount must be greater or equal to zero");
        transferEthAmount = _amount;
    }
}


EvmFaucet

// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v4.7.0) (access/Ownable.sol)

pragma solidity ^0.8.0;

import "../utils/Context.sol";

/**
 * @dev Contract module which provides a basic access control mechanism, where
 * there is an account (an owner) that can be granted exclusive access to
 * specific functions.
 *
 * By default, the owner account will be the one that deploys the contract. This
 * can later be changed with {transferOwnership}.
 *
 * This module is used through inheritance. It will make available the modifier
 * `onlyOwner`, which can be applied to your functions to restrict their use to
 * the owner.
 */
abstract contract Ownable is Context {
    address private _owner;

    event OwnershipTransferred(address indexed previousOwner, address indexed newOwner);

    /**
     * @dev Initializes the contract setting the deployer as the initial owner.
     */
    constructor() {
        _transferOwnership(_msgSender());
    }

    /**
     * @dev Throws if called by any account other than the owner.
     */
    modifier onlyOwner() {
        _checkOwner();
        _;
    }

    /**
     * @dev Returns the address of the current owner.
     */
    function owner() public view virtual returns (address) {
        return _owner;
    }

    /**
     * @dev Throws if the sender is not the owner.
     */
    function _checkOwner() internal view virtual {
        require(owner() == _msgSender(), "Ownable: caller is not the owner");
    }

    /**
     * @dev Leaves the contract without owner. It will not be possible to call
     * `onlyOwner` functions anymore. Can only be called by the current owner.
     *
     * NOTE: Renouncing ownership will leave the contract without an owner,
     * thereby removing any functionality that is only available to the owner.
     */
    function renounceOwnership() public virtual onlyOwner {
        _transferOwnership(address(0));
    }

    /**
     * @dev Transfers ownership of the contract to a new account (`newOwner`).
     * Can only be called by the current owner.
     */
    function transferOwnership(address newOwner) public virtual onlyOwner {
        require(newOwner != address(0), "Ownable: new owner is the zero address");
        _transferOwnership(newOwner);
    }

    /**
     * @dev Transfers ownership of the contract to a new account (`newOwner`).
     * Internal function without access restriction.
     */
    function _transferOwnership(address newOwner) internal virtual {
        address oldOwner = _owner;
        _owner = newOwner;
        emit OwnershipTransferred(oldOwner, newOwner);
    }
}


// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts v4.4.1 (utils/Context.sol)

pragma solidity ^0.8.0;

/**
 * @dev Provides information about the current execution context, including the
 * sender of the transaction and its data. While these are generally available
 * via msg.sender and msg.data, they should not be accessed in such a direct
 * manner, since when dealing with meta-transactions the account sending and
 * paying for execution may not be the actual sender (as far as an application
 * is concerned).
 *
 * This contract is only required for intermediate, library-like contracts.
 */
abstract contract Context {
    function _msgSender() internal view virtual returns (address) {
        return msg.sender;
    }

    function _msgData() internal view virtual returns (bytes calldata) {
        return msg.data;
    }
}


A faucet contract that allows users to request a small amount of ETH. Users can request ETH once every 24 hours. The contract has a balance that can be funded by the owner. The owner can also change the amount of ETH given on each request

ETH Faucet

Returns the address of the current owner.

Leaves the contract without owner. It will not be possible to call `onlyOwner` functions anymore. Can only be called by the current owner. NOTE: Renouncing ownership will leave the contract without an owner, thereby removing any functionality that is only available to the owner.

function to request a small amount of ETHThe function checks if the contract has enough balanceThe function also checks if the user has requested beforeIf all the conditions are met, the function will transfer the amount stored in transferEthAmount to the user address
- _to: address to send the eth

function that allows the owner to change the value of the transferEthAmountThe function will be executed only by the owner of the contract
- _amount: new amount that should be equal or greater than zero

Transfers ownership of the contract to a new account (`newOwner`). Can only be called by the current owner.

function that allows the owner to withdraw the contract balancethe function checks that the contract has a balance greater than zeroThe function will be executed only by the owner of the contract