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Jordi Planes 5 years ago
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1 changed files with 149 additions and 0 deletions
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      contract.sol

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contract.sol View File

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+pragma solidity ^0.4.22;
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+
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+/// @title Voting with delegation.
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+contract Ballot {
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+    // This declares a new complex type which will
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+    // be used for variables later.
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+    // It will represent a single voter.
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+    struct Voter {
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+        uint weight; // weight is accumulated by delegation
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+        bool voted;  // if true, that person already voted
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+        address delegate; // person delegated to
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+        uint vote;   // index of the voted proposal
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+    }
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+
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+    // This is a type for a single proposal.
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+    struct Proposal {
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+        bytes32 name;   // short name (up to 32 bytes)
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+        uint voteCount; // number of accumulated votes
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+    }
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+
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+    address public chairperson;
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+
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+    // This declares a state variable that
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+    // stores a `Voter` struct for each possible address.
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+    mapping(address => Voter) public voters;
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+
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+    // A dynamically-sized array of `Proposal` structs.
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+    Proposal[] public proposals;
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+
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+    /// Create a new ballot to choose one of `proposalNames`.
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+    constructor(bytes32[] proposalNames) public {
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+        chairperson = msg.sender;
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+        voters[chairperson].weight = 1;
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+
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+        // For each of the provided proposal names,
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+        // create a new proposal object and add it
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+        // to the end of the array.
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+        for (uint i = 0; i < proposalNames.length; i++) {
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+            // `Proposal({...})` creates a temporary
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+            // Proposal object and `proposals.push(...)`
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+            // appends it to the end of `proposals`.
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+            proposals.push(Proposal({
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+                name: proposalNames[i],
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+                voteCount: 0
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+            }));
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+        }
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+    }
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+
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+    // Give `voter` the right to vote on this ballot.
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+    // May only be called by `chairperson`.
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+    function giveRightToVote(address voter) public {
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+        // If the first argument of `require` evaluates
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+        // to `false`, execution terminates and all
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+        // changes to the state and to Ether balances
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+        // are reverted.
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+        // This used to consume all gas in old EVM versions, but
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+        // not anymore.
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+        // It is often a good idea to use `require` to check if
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+        // functions are called correctly.
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+        // As a second argument, you can also provide an
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+        // explanation about what went wrong.
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+        require(
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+            msg.sender == chairperson,
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+            "Only chairperson can give right to vote."
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+        );
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+        require(
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+            !voters[voter].voted,
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+            "The voter already voted."
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+        );
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+        require(voters[voter].weight == 0);
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+        voters[voter].weight = 1;
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+    }
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+
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+    /// Delegate your vote to the voter `to`.
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+    function delegate(address to) public {
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+        // assigns reference
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+        Voter storage sender = voters[msg.sender];
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+        require(!sender.voted, "You already voted.");
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+
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+        require(to != msg.sender, "Self-delegation is disallowed.");
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+
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+        // Forward the delegation as long as
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+        // `to` also delegated.
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+        // In general, such loops are very dangerous,
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+        // because if they run too long, they might
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+        // need more gas than is available in a block.
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+        // In this case, the delegation will not be executed,
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+        // but in other situations, such loops might
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+        // cause a contract to get "stuck" completely.
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+        while (voters[to].delegate != address(0)) {
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+            to = voters[to].delegate;
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+
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+            // We found a loop in the delegation, not allowed.
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+            require(to != msg.sender, "Found loop in delegation.");
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+        }
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+
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+        // Since `sender` is a reference, this
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+        // modifies `voters[msg.sender].voted`
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+        sender.voted = true;
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+        sender.delegate = to;
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+        Voter storage delegate_ = voters[to];
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+        if (delegate_.voted) {
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+            // If the delegate already voted,
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+            // directly add to the number of votes
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+            proposals[delegate_.vote].voteCount += sender.weight;
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+        } else {
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+            // If the delegate did not vote yet,
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+            // add to her weight.
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+            delegate_.weight += sender.weight;
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+        }
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+    }
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+
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+    /// Give your vote (including votes delegated to you)
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+    /// to proposal `proposals[proposal].name`.
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+    function vote(uint proposal) public {
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+        Voter storage sender = voters[msg.sender];
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+        require(!sender.voted, "Already voted.");
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+        sender.voted = true;
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+        sender.vote = proposal;
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+
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+        // If `proposal` is out of the range of the array,
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+        // this will throw automatically and revert all
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+        // changes.
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+        proposals[proposal].voteCount += sender.weight;
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+    }
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+
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+    /// @dev Computes the winning proposal taking all
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+    /// previous votes into account.
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+    function winningProposal() public view
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+            returns (uint winningProposal_)
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+    {
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+        uint winningVoteCount = 0;
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+        for (uint p = 0; p < proposals.length; p++) {
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+            if (proposals[p].voteCount > winningVoteCount) {
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+                winningVoteCount = proposals[p].voteCount;
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+                winningProposal_ = p;
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+            }
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+        }
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+    }
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+
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+    // Calls winningProposal() function to get the index
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+    // of the winner contained in the proposals array and then
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+    // returns the name of the winner
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+    function winnerName() public view
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+            returns (bytes32 winnerName_)
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+    {
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+        winnerName_ = proposals[winningProposal()].name;
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+    }
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+}

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