【区块链笔记】ETH_Solidity简单投票合约(05)

pragma solidity ^0.4.0;

contract Ballot {
    
    struct Voter {
       uint weight;
       bool voted;
       uint8 vote;
       address delegate; 
    }
    struct Proposal {
        uint voteCount;
    }

    address chairperson;
    mapping(address => Voter) voters;
    Proposal[] proposals;

    function Ballot(uint8 _numProposals) public {
        chairperson = msg.sender;
        voters[chairperson].weight = 1;
        proposals.length = _numProposals;
    }

    //授权投票
    function giveRightToVote(address toVoter) public {
        if (msg.sender != chairperson || voters[toVoter].voted) return;
        voters[toVoter].weight = 1;
    }

    //委托投票
    function delegate(address to) public {
        Voter storage sender = voters[msg.sender];
        if (sender.voted) return;
        while (voters[to].delegate != address(0) && voters[to].delegate != msg.sender)
            to = voters[to].delegate;
        if (to == msg.sender) return;
        sender.voted = true;
        sender.delegate = to;
        Voter storage delegateTo = voters[to];
        if (delegateTo.voted)
            proposals[delegateTo.vote].voteCount += sender.weight;
        else
            delegateTo.weight +=sender.weight;
    }

    function vote(uint8 toProposal) public {
        Voter storage sender = voters[msg.sender];
        if (sender.voted || toProposal > proposals.length) return;
        sender.voted = true;
        sender.vote = toProposal;
        proposals[toProposal].voteCount += sender.weight;
    }

    function winningProposal() public constant returns (uint _winningProposal){
        uint256 winningVoteCount = 0;
        for(uint prop = 0; prop < proposals.length; prop++)
            if (proposals[prop].voteCount > winningVoteCount){
                winningVoteCount = proposals[prop].voteCount;
                _winningProposal = prop;
            }
    }
}