Blockchain Basics

pragma solidity ~0.8.0; //솔리디티 컴파일러 버전 설정 contract Fundraising{ uint256 public targetAmount; //unsigned 256비트 정수 //string이지만 이더리움 주소의 올바른 형식이어야함. 프로젝트 소유자 지갑주소 address public owner; mapping(address => uint256) public donations; //기부한 사람들 주소와 액수 맵 uint256 public raisedAmount = 0; //block은 EVM에 의해 정의되는 객체. 블록이 생성되는 날짜로부터 2주후까지 uint256 public finishTime = block.timestamp + 2 weeks; //constructor에서 초기화 constructor(uint256 _targetAmout){ //contract을 배포할때 얼마로 목표를 설정할지 정한다 targetAmount = _targetAmount //msg.sender도 EVM에 의해서 정의되며 컨트랙을 작성하는 행위자의 주소 owner = msg.sender; } //컨트랙의 외부에서만 호출할 수 있다 //payable은 돈을 받을 수 있다는것을 나타냄 //누군가 돈을 보내려고 receive함수를 호출하면 실행된다 //다른 컴퓨터의 메소드를 호출하기때문에 RPC를 사용하는것 receive() external payable{ require(block.timestamp < finishTime, "This is over"); //누군가 돈을 보냈는데 끝나지 않은 경우 돈을 보낸 사람의 주소와 금액 추가 donations[msg.sender] +=msg.value; raisedAmount += msg.value; } function withdrawDonations() external { //함수를 호출한 사람과 owner가 동일한 사람인지 확인함 require(msg.sender == owner, "Fund will only be released by owner"); require(raisedAmount >=targetAmount, "The Project did not reach the goal"); require(block.timestamp > finishTime, "The campaign is not over yet"); payable(owner).transfer(raisedAmount); } function refund() extermal{ require(block.timestamp > finishTime, "The campaign is not over yet"); require(raisedAmount < targetAmount, "The camapign reached the goal"); require(donations[msg.sender] > 0, "You didn't participate"); uint toRefund = donations[msg.sender]; donations[msg.sender]=0; payable(msg.sender).transfer(toRefund); } }

//hardhat.config.js require("@nomiclabs/hardhat-waffle"); task("check","check contract amounts", async() => { const contract="0x컨트랙주소" const abi = [ ... ] }) module.exports = { solidity: "0.8.0", networks: { sepolia: { url: "https://ethereum-sepolia.g.allthatnode.com/full/evm/..." accounts: [""], }, }, };

//deploy.js async function main() { //ethers.js를 사용해서 Fundraising 컨트랙을 가져와서 컴파일하고 const Fundraising = await ethers.getContractFactory("Fundraising"); //인자(targetAmount)와 함께 배포한다. const contract = await Fundraising.deploy(10000000000); //배포이후 컨트랙 주소를 blockchain explorer에서 확인해볼수 있도록 log console.log("Contract address is : ", contract.address); } main() .then(() => process.exit(0)) .catch((error) => { console.error(error); process.exit(1); });

pragma solidity >=0.4.0 <0.6.0; contract SimpleStorage { uint storedData; function set(uint x) public { storedData = x; } function get() public view returns (uint) { return storedData; } }

pragma solidity ^0.5.0; contract Coin { // The keyword "public" makes those variables // easily readable from outside. address public minter; mapping (address => uint) public balances; event Sent(address from, address to, uint amount); // This is the constructor whose code is // run only when the contract is created. constructor() public { minter = msg.sender; } function mint(address receiver, uint amount) public { require(msg.sender == minter); require(amount < 1e60); balances[receiver] += amount; } function send(address receiver, uint amount) public { require(amount <= balances[msg.sender], "Insufficient balance."); balances[msg.sender] -= amount; balances[receiver] += amount; emit Sent(msg.sender, receiver, amount); } }

function mint(address receiver, uint amount) public { require(msg.sender == minter); require(amount < 1e60); balances[receiver] += amount; }

function send(address receiver, uint amount) public { require(amount <= balances[msg.sender], "Insufficient balance."); balances[msg.sender] -= amount; balances[receiver] += amount; emit Sent(msg.sender, receiver, amount); }