基於以太坊的投票系統(Solidity by Example —— Voting)
阿新 • • 發佈:2019-01-10
原文如下
pragma solidity ^0.4.16; /// @title Voting with delegation. contract Ballot { // This declares a new complex type which will // be used for variables later. // It will represent a single voter. struct Voter { uint weight; // weight is accumulated by delegation bool voted; // if true, that person already votedaddress delegate; // person delegated to uint vote; // index of the voted proposal } // This is a type for a single proposal. struct Proposal { bytes32 name; // short name (up to 32 bytes) uint voteCount; // number of accumulated votes } address publicchairperson; // This declares a state variable that // stores a `Voter` struct for each possible address. mapping(address => Voter) public voters; // A dynamically-sized array of `Proposal` structs. Proposal[] public proposals; /// Create a new ballot to choose one of `proposalNames`.function Ballot(bytes32[] proposalNames) public { chairperson = msg.sender; voters[chairperson].weight = 1; // For each of the provided proposal names, // create a new proposal object and add it // to the end of the array. for (uint i = 0; i < proposalNames.length; i++) { // `Proposal({...})` creates a temporary // Proposal object and `proposals.push(...)` // appends it to the end of `proposals`. proposals.push(Proposal({ name: proposalNames[i], voteCount: 0 })); } } // Give `voter` the right to vote on this ballot. // May only be called by `chairperson`. function giveRightToVote(address voter) public { // If the argument of `require` evaluates to `false`, // it terminates and reverts all changes to // the state and to Ether balances. It is often // a good idea to use this if functions are // called incorrectly. But watch out, this // will currently also consume all provided gas // (this is planned to change in the future). require( (msg.sender == chairperson) && !voters[voter].voted && (voters[voter].weight == 0) ); voters[voter].weight = 1; } /// Delegate your vote to the voter `to`. function delegate(address to) public { // assigns reference Voter storage sender = voters[msg.sender]; require(!sender.voted); // Self-delegation is not allowed. require(to != msg.sender); // Forward the delegation as long as // `to` also delegated. // In general, such loops are very dangerous, // because if they run too long, they might // need more gas than is available in a block. // In this case, the delegation will not be executed, // but in other situations, such loops might // cause a contract to get "stuck" completely. while (voters[to].delegate != address(0)) { to = voters[to].delegate; // We found a loop in the delegation, not allowed. require(to != msg.sender); } // Since `sender` is a reference, this // modifies `voters[msg.sender].voted` sender.voted = true; sender.delegate = to; Voter storage delegate_ = voters[to]; if (delegate_.voted) { // If the delegate already voted, // directly add to the number of votes proposals[delegate_.vote].voteCount += sender.weight; } else { // If the delegate did not vote yet, // add to her weight. delegate_.weight += sender.weight; } } /// Give your vote (including votes delegated to you) /// to proposal `proposals[proposal].name`. function vote(uint proposal) public { Voter storage sender = voters[msg.sender]; require(!sender.voted); sender.voted = true; sender.vote = proposal; // If `proposal` is out of the range of the array, // this will throw automatically and revert all // changes. proposals[proposal].voteCount += sender.weight; } /// @dev Computes the winning proposal taking all /// previous votes into account. function winningProposal() public view returns (uint winningProposal_) { uint winningVoteCount = 0; for (uint p = 0; p < proposals.length; p++) { if (proposals[p].voteCount > winningVoteCount) { winningVoteCount = proposals[p].voteCount; winningProposal_ = p; } } } // Calls winningProposal() function to get the index // of the winner contained in the proposals array and then // returns the name of the winner function winnerName() public view returns (bytes32 winnerName_) { winnerName_ = proposals[winningProposal()].name; } }
中文註釋:
pragmasolidity^0.4.16; //註釋Solidity版本 //合約名 contract Ballot { // 投票者結構體 struct Voter { uint weight; // 份額(既擁有多少票) bool voted; // 是否已經投票 address delegate; // 委任誰進行投票 uint vote; // 第幾個投票議案 } // 議案機構體 struct Proposal { bytes32 name; // 議案名(最多32位元組) uint voteCount; // 累計投票數 } address public chairperson; //投票主持人 // 投票者與其地址的對映 mapping(address => Voter) public voters; // 提案指標 Proposal[] public proposals; /// Ballot函式,建立新投票,輸入多個議案名 function Ballot(bytes32[] proposalNames) public { chairperson = msg.sender; voters[chairperson].weight = 1; for (uint i = 0; i < proposalNames.length; i++) { // `Proposal({...})` 建立一個臨時Proposal物件 proposals.push(Proposal({ name: proposalNames[i], voteCount: 0 })); } } //輸入投票者地址,給予投票者投票許可權 function giveRightToVote(address voter) public { // require防止函式被錯誤呼叫,判斷為錯誤時終止呼叫 // 並恢復到呼叫前的狀態,但是注意會消耗gas require( (msg.sender == chairperson) && !voters[voter].voted && (voters[voter].weight == 0) ); voters[voter].weight = 1; } /// 輸入他人地址,委任他人投票 function delegate(address to) public { Voter storage sender = voters[msg.sender]; require(!sender.voted); // 不允許委任自己 require(to != msg.sender); // 迴圈委任直至被委任人不再委任他人, // 但注意這種迴圈是危險的,有可能耗盡gas來進行計算。 while (voters[to].delegate != address(0)) { to = voters[to].delegate; // 避免迴圈委任,形成委任環鏈 require(to != msg.sender); } // 此處sender為voters[msg.sender] sender.voted = true; sender.delegate = to; Voter storage delegate_ = voters[to]; if (delegate_.voted) { // 如果被委任人已經投票,直接增加該議案票數 proposals[delegate_.vote].voteCount += sender.weight; } else { // 如果被委任人未投票,增加被委任人持有票數 delegate_.weight += sender.weight; } } /// 向議案投票 function vote(uint proposal) public { Voter storage sender = voters[msg.sender]; require(!sender.voted); sender.voted = true; sender.vote = proposal; // 提案超出陣列範圍時自動中斷並恢復所以修改 proposals[proposal].voteCount += sender.weight; } /// 返回獲得票數最高的議案索引 function winningProposal() public view returns (uint winningProposal_) { uint winningVoteCount = 0; for (uint p = 0; p < proposals.length; p++) { if (proposals[p].voteCount > winningVoteCount) { winningVoteCount = proposals[p].voteCount; winningProposal_ = p; } } } // 返回獲得票數最高的議案名 function winnerName() public view returns (bytes32 winnerName_) { winnerName_ = proposals[winningProposal()].name; } }