https://github.com/leye195/simple_votingdapp
Ganache 활용 간단한 VotingDapp
https://github.com/leye195/simple_votingdapp
html-css javascript solidity
Last synced: 2 months ago
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Ganache 활용 간단한 VotingDapp
- Host: GitHub
- URL: https://github.com/leye195/simple_votingdapp
- Owner: leye195
- Created: 2021-01-31T14:47:17.000Z (over 4 years ago)
- Default Branch: master
- Last Pushed: 2021-01-31T14:52:03.000Z (over 4 years ago)
- Last Synced: 2025-02-06T23:31:27.143Z (4 months ago)
- Topics: html-css, javascript, solidity
- Language: JavaScript
- Homepage:
- Size: 14.9 MB
- Stars: 0
- Watchers: 2
- Forks: 0
- Open Issues: 0
-
Metadata Files:
- Readme: README.md
Awesome Lists containing this project
README
# Simple Voting Dapp
- Ganache를 활용한 Simple Voting Dapp 실습
### Web3 인스턴스 생성
```js
const Web3 = require("web3");
const web3 = new Web3(new Web3.providers.HttpProvider("http://localhost:8545"));
console.log(web3.eth.accounts); //account 목록 출력
console.log(web3.eth.getBalance(account).toNumber()); //해당 계정이 소유하고 있는 밸런스 출력
//출력하는 값의 단위는 wei (1eth = 10^18 wei) 이기 때문에 출력값/10^18을 해줘야 소유하고 있는
//eth의 양을 확인 할 수 있음
console.log(web3.fromWei(100000000000000000000, "ether")); //100 출력
//eth 단위로 환산
//위 코드를 축약하면 아래 형식으로 작성 가능
web3.fromWei(
web3.eth.getBalance("0x352e047734a52bff0e95969d80a02300f9551c15").toNumber(),
"ether"
);
```
### Solidity로 Contract 작성
```
//remix를 활용해 contract 작성
pragma solidity ^0.4.23;
contract Voting {
bytes32[] public candidateList;
mapping (bytes32 => uint8) voteReceived;
// ex) nick => 5 , Dan => 4
//생성자는 컨트랙트가 배포될 때 딱 한 번만 초기화되며, 같은 소스의 컨트랙트를 여러번 배포할 경우
//서로 다른 인스턴스가 블록체인 상에 여러개가 생기게 될 뿐
constructor(bytes32[] candidateNames) {
candidateList = candidateNames;
}
function voteForCandidate(bytes32 candidate) public {
//require문을 활용해 유효 체크, true인 경우 다음 코드 실행, false인 경우 끝
require(validCandidate(candidate),'There is no such candidate on the list');
voteReceived[candidate]+=1;
}
//view는 읽기 전용을 의미, returns(type)는 함수가 리턴할 타입을 명시
function totalVotesFor(bytes32 candidate) view public returns(uint8) {
require(validCandidate(candidate));
return voteReceived[candidate];
}
//candidate가 유효한지 체크
function validCandidate(bytes32 candidate) view public return(bool) {
for(uint i=0;iweb3.utils.asciiToHex(name))]
}).send({
from: '0x352e047734a52bFf0e95969d80A02300f9551C15',
gas: 1500000,
gasPrice: web3.utils.toWei('0.00001','ether')
}).then((newContractInstance) => {
deployedContract.options.address = newContractInstance.options.address;
});
deployedContract.options.address; //컨트랙트 주소
deployedContract.methods; //배포한 컨트랙트 함수 목록
```
4.컨트랙트와 상호작용
```js
/*
.call: 읽기 전용일 경우에만 호출해 활용
.send: 일반 호출, 블록체인의 상태를 변화 시키는 경우
읽기 전용 호출와 일반 호출의 차이는 블록체인의 상태를 바꾸는가 아닌가의 차이
*/
//ex)
deployedContract.methods
.totalVotesFor(web3.utils.asciiToHex("dan"))
.call()
.then((count) => console.log(count));
deployedContract.methods
.voteForCandidate(web3.utils.asciiToHex("dan"))
.send({ from: web3.eth.accounts[0] })
.then((res) => console.log(res));
```
5.프론트엔드 구현 및 호출
```js
//ex) 아래와 같은 방식으로 작성
const web3 = new Web3(new Web3.providers.HttpProvider("http://localhost:8545"));
const contractAddress = "0xb2f02628d8D38B14288ec53eCbF482a433fa214b";
const abi = JSON.parse(
'[{"constant":true,"inputs":[{"name":"candidate","type":"bytes32"}],"name":"totalVotesFor","outputs":[{"name":"","type":"uint8"}],"payable":false,"stateMutability":"view","type":"function"},{"constant":true,"inputs":[{"name":"candidate","type":"bytes32"}],"name":"validCandidate","outputs":[{"name":"","type":"bool"}],"payable":false,"stateMutability":"view","type":"function"},{"constant":true,"inputs":[{"name":"","type":"uint256"}],"name":"candidateList","outputs":[{"name":"","type":"bytes32"}],"payable":false,"stateMutability":"view","type":"function"},{"constant":false,"inputs":[{"name":"candidate","type":"bytes32"}],"name":"voteForCandidate","outputs":[],"payable":false,"stateMutability":"nonpayable","type":"function"},{"inputs":[{"name":"candidateNames","type":"bytes32[]"}],"payable":false,"stateMutability":"nonpayable","type":"constructor"}]'
);
const votingContract = new web3.eth.Contract(abi, contractAddress);
const candidates = {
dan: "candidate-1",
lee: "candidate-2",
ben: "candidate-3",
};
const voteButton = document.querySelector(".vote_button");
let account = null;
const voteForCandidate = () => {
const candidateInput = document.querySelector("#candidate");
const candidateName = candidateInput.value.toLowerCase();
votingContract.methods
.voteForCandidate(web3.utils.asciiToHex(candidateName))
.send({ from: account, gas: 4700000 })
.then(() => {
let id = candidates[candidateName];
votingContract.methods
.totalVotesFor(web3.utils.asciiToHex(candidateName))
.call()
.then((count) => {
const candidate = document.querySelector(`#${id}`);
candidate.textContent = count;
candidateInput.value = "";
});
});
};
const init = () => {
web3.eth.getAccounts((err, accounts) => {
if (err) {
alert("There was an error fetching your accounts.");
return;
}
if (accounts.length === 0) {
alert(
"Couldn't get any accounts! Make sure your Ethereum client is configured correctly."
);
return;
}
account = accounts[0];
});
const candidateNames = Object.keys(candidates);
candidateNames.forEach((candidate) => {
votingContract.methods
.totalVotesFor(web3.utils.asciiToHex(candidate))
.call()
.then((count) => {
document.querySelector(`#${candidates[candidate]}`).textContent = count;
});
});
voteButton.addEventListener("click", voteForCandidate);
};
window.onload = () => {
init();
};
```