[BlockChain] 스마트컨트랙트로 투표 Dapp 만들기

1. 초기설정

npx truffle init

다른 터미널로 가나쉬 실행

npx ganache-cli

truffle-config.js

module.exports = {
  networks: {
    development: {
      host: "127.0.0.1",
      port: 8545,
      network_id: "*",
    },
  },
  compilers: {
    solc: {
      version: "0.8.17",
    },
  },
};

2. 스마트 컨트랙트

/contracts/Voting.sol

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.17;

contract Voting{
    string[] public candidateList;
    mapping(string=> uint8) public votessReceived;

    constructor(string[] memory candidateNames){
        candidateList = candidateNames;
    }

    // 후보자 표 갯수 확인
    function totalVotesFor(string memory candidate) public view returns(uint8){
        require(validCandidate((candidate)));
        return votessReceived[candidate];
    }
    
    // 후보자 투표해주는 함수
    function voteForCandidate(string memory candidate) public{
        require(validCandidate((candidate)));
        votessReceived[candidate] += 1;
    }

    // 후보자 있는 후보자인지 확인 검증
    function validCandidate(string memory candidate) private view returns(bool){
        for(uint i = 0 ; i < candidateList.length; i++){
            if(keccak256(abi.encodePacked(candidateList[i])) == keccak256(abi.encodePacked(candidate))){
                return true;
            }
        }
        return false;
    }
}

3. 배포

/migrations/2_deploy_Voting.js

const Voting = artifacts.require("Voting");

module.exports = function (deployer) {
  deployer.deploy(Voting, ["후보자1", "후보자2", "후보자3"]);
};

배포

npx truffle migration

4. 테스트

/test/voting.test.js

const Voting = artifacts.require("Voting");

describe.only("Voting", () => {
  let deployed; // 배포 컨트랙트 객체
  let candidateList; // 후보자 리스트

  it("deployed", async () => {
    deployed = await Voting.deployed();
  });

  it("후보자 리스트 확인", async () => {
    const req = [
      deployed.candidateList.call(0),
      deployed.candidateList.call(1),
      deployed.candidateList.call(2),
    ];
    candidateList = await Promise.all(req);

    console.log(candidateList);
  });

  it("투표, 투표수 확인", async () => {
    await deployed.voteForCandidate(candidateList[1]);
    await deployed.voteForCandidate(candidateList[1]);
    await deployed.voteForCandidate(candidateList[0]);
    await deployed.voteForCandidate(candidateList[0]);
    for (const key of candidateList) {
      let count = await deployed.totalVotesFor(key);
      console.log(`${key} : ${count}`);
    }
  }).timeout(10000);
});