事件（Events）：

• VotedEvent: 当有人投票时触发,记录投票人地址和候选人。

函数（Functions）：

• constructor(): 构造函数，初始化合约所有者,设置投票时间。
• addCandidate(string memory candidateName): 仅合约所有者可调用,添加候选人。
• vote(string memory candidateName): 核心投票函数，检查投票时间、候选人是否存在、投票人是否已投票,通过后更新票数并标记投票人。
• getVotes(string memory candidateName) public view returns (uint256): 查询指定候选人的得票数。
• getWinner() public view returns (string memory): 获取当前得票最多的候选人（投票结束后）。

Solidity代码示例（简化版）：

pragma solidity ^0.8.0;
contract Voting {
    address public votingContractOwner;
    mapping(string => uint256) public candidates;
    mapping(address => bool) public voters;
    uint256 public votingStartTime;
    uint256 public votingEndTime;
    event VotedEvent(address voter, string candidate);
    constructor(uint256 _votingDurationSeconds) {
        votingContractOwner = msg.sender;
        votingStartTime = block.timestamp;
        votingEndTime = block.timestamp + _votingDurationSeconds;
    }
    modifier onlyOwner() {
        require(msg.sender == votingContractOwner, "Only owner can call this function");
        _;
    }
    modifier duringVoting() {
        require(block.timestamp >= votingStartTime && block.timestamp <= votingEndTime, "Voting is not active");
        _;
    }
    function addCandidate(string memory candidateName) public onlyOwner {
        require(bytes(candidateName).length > 0, "Candidate name cannot be empty");
        require(candidates[candidateName] == 0, "Candidate already exists");
        candidates[candidateName] = 0;
    }
    function vote(string memory candidateName) public duringVoting {
        require(!voters[msg.sender], "You have already voted");
        require(candidates[candidateName] > 0, "Candidate does not exist");
        voters[msg.sender] = true;
        candidates[candidateName] += 1;
        emit VotedEvent(msg.sender, candidateName);
    }
    function getVotes(string memory candidateName) public view returns (uint256) {
        return candidates[candidateName];
    }
    function getWinner() public view returns (string memory) {
        uint256 maxVotes = 0;
        string memory winner;
        for (uint256 i = 0; i < candidateNames.length; i++) {
            string memory memoryCandidateName = candidateNames[i];
            if (candidates[memoryCandidateName] > maxVotes) {
                maxVotes = candidates[memoryCandidateName];
                winner = memoryCandidateName;
            }
        }
        return winner;
    }
}

前端应用实现

• 用户界面： 包含候选人列表、投票按钮、投票结果显示区域、连接MetaMask按钮等。
• 交互逻辑： 使用Web3.js连接到以太坊节点，加载已部署的智能合约实例。
  • 用户点击“连接钱包”按钮，MetaMask弹出请求，用户授权后,前端获取用户账户地址。
  • 合约所有者可通过前端调用addCandidate添加候选人。
  • 普通用户选择候选人后，点击“投票”按钮，调用vote函数，MetaMask弹出交易确认框,用户确认后发送交易。
  • 前端实时或定时调用getVotes和getWinner函数,更新投票结果。