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@ -7,7 +7,9 @@ pragma solidity >=0.7.0 <0.9.0; |
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* @dev Implements voting process along with vote delegation |
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* @dev Implements voting process along with vote delegation |
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*/ |
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*/ |
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contract Ballot { |
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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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struct Voter { |
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uint weight; // weight is accumulated by delegation |
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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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bool voted; // if true, that person already voted |
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@ -15,6 +17,7 @@ contract Ballot { |
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uint vote; // index of the voted proposal |
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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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struct Proposal { |
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// If you can limit the length to a certain number of bytes, |
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// If you can limit the length to a certain number of bytes, |
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// always use one of bytes1 to bytes32 because they are much cheaper |
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// always use one of bytes1 to bytes32 because they are much cheaper |
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@ -24,8 +27,11 @@ contract Ballot { |
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address public chairperson; |
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address public chairperson; |
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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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mapping(address => Voter) public voters; |
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// A dynamically-sized array of 'Proposal' structs. |
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Proposal[] public proposals; |
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Proposal[] public proposals; |
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/** |
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/** |
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@ -36,6 +42,9 @@ contract Ballot { |
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chairperson = msg.sender; |
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chairperson = msg.sender; |
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voters[chairperson].weight = 1; |
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voters[chairperson].weight = 1; |
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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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for (uint i = 0; i < proposalNames.length; i++) { |
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// 'Proposal({...})' creates a temporary |
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// 'Proposal({...})' creates a temporary |
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// Proposal object and 'proposals.push(...)' |
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// Proposal object and 'proposals.push(...)' |
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@ -47,11 +56,21 @@ contract Ballot { |
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} |
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} |
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} |
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} |
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/** |
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/** |
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* @dev Give 'voter' the right to vote on this ballot. May only be called by 'chairperson'. |
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* @dev Give 'voter' the right to vote on this ballot. May only be called by 'chairperson'. |
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* @param voter address of voter |
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* @param voter address of voter |
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*/ |
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*/ |
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function giveRightToVote(address voter) public { |
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function giveRightToVote(address voter) external { |
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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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require( |
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msg.sender == chairperson, |
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msg.sender == chairperson, |
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"Only chairperson can give right to vote." |
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"Only chairperson can give right to vote." |
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@ -60,7 +79,7 @@ contract Ballot { |
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!voters[voter].voted, |
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!voters[voter].voted, |
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"The voter already voted." |
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"The voter already voted." |
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); |
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); |
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require(voters[voter].weight == 0); |
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require(voters[voter].weight == 0, "Voter already has the right to vote."); |
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voters[voter].weight = 1; |
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voters[voter].weight = 1; |
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} |
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} |
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@ -68,20 +87,39 @@ contract Ballot { |
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* @dev Delegate your vote to the voter 'to'. |
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* @dev Delegate your vote to the voter 'to'. |
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* @param to address to which vote is delegated |
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* @param to address to which vote is delegated |
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*/ |
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*/ |
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function delegate(address to) public { |
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function delegate(address to) external { |
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// assigns reference |
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Voter storage sender = voters[msg.sender]; |
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Voter storage sender = voters[msg.sender]; |
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require(sender.weight != 0, "You have no right to vote"); |
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require(!sender.voted, "You already voted."); |
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require(!sender.voted, "You already voted."); |
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require(to != msg.sender, "Self-delegation is disallowed."); |
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require(to != msg.sender, "Self-delegation is disallowed."); |
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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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while (voters[to].delegate != address(0)) { |
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to = voters[to].delegate; |
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to = voters[to].delegate; |
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// We found a loop in the delegation, not allowed. |
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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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require(to != msg.sender, "Found loop in delegation."); |
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} |
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} |
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Voter storage delegate_ = voters[to]; |
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// Voters cannot delegate to accounts that cannot vote. |
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require(delegate_.weight >= 1); |
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// Since 'sender' is a reference, this |
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// modifies 'voters[msg.sender]'. |
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sender.voted = true; |
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sender.voted = true; |
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sender.delegate = to; |
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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 (delegate_.voted) { |
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// If the delegate already 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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// directly add to the number of votes |
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@ -97,7 +135,7 @@ contract Ballot { |
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* @dev Give your vote (including votes delegated to you) to proposal 'proposals[proposal].name'. |
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* @dev Give your vote (including votes delegated to you) to proposal 'proposals[proposal].name'. |
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* @param proposal index of proposal in the proposals array |
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* @param proposal index of proposal in the proposals array |
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*/ |
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*/ |
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function vote(uint proposal) public { |
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function vote(uint proposal) external { |
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Voter storage sender = voters[msg.sender]; |
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Voter storage sender = voters[msg.sender]; |
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require(sender.weight != 0, "Has no right to vote"); |
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require(sender.weight != 0, "Has no right to vote"); |
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require(!sender.voted, "Already voted."); |
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require(!sender.voted, "Already voted."); |
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@ -130,7 +168,7 @@ contract Ballot { |
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* @dev Calls winningProposal() function to get the index of the winner contained in the proposals array and then |
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* @dev Calls winningProposal() function to get the index of the winner contained in the proposals array and then |
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* @return winnerName_ the name of the winner |
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* @return winnerName_ the name of the winner |
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*/ |
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*/ |
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function winnerName() public view |
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function winnerName() external view |
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returns (bytes32 winnerName_) |
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returns (bytes32 winnerName_) |
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{ |
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{ |
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winnerName_ = proposals[winningProposal()].name; |
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winnerName_ = proposals[winningProposal()].name; |
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