voting period
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// SPDX-License-Identifier: GPL-3.0
// SPDX-License-Identifier: GPL-3.0
pragma solidity >=0.7.0 <0.9.0;
pragma solidity >=0.7.0 <0.9.0;
/// @title Voting with delegation.
/// @title Voting with delegation.
contract Ballot {
contract Ballot {
// This declares a new complex type which will
// This declares a new complex type which will
// be used for variables later.
// be used for variables later.
// It will represent a single voter.
// It will represent a single voter.
struct Voter {
struct Voter {
uint weight; // weight is accumulated by delegation
uint weight; // weight is accumulated by delegation
bool voted; // if true, that person already voted
bool voted; // if true, that person already voted
address delegate; // person delegated to
address delegate; // person delegated to
uint vote; // index of the voted proposal
uint vote; // index of the voted proposal
}
}
// This is a type for a single proposal.
// This is a type for a single proposal.
struct Proposal {
struct Proposal {
bytes32 name; // short name (up to 32 bytes)
bytes32 name; // short name (up to 32 bytes)
uint voteCount; // number of accumulated votes
uint voteCount; // number of accumulated votes
}
}
address public chairperson;
address public chairperson;
uint256 public startTime;
// This declares a state variable that
// This declares a state variable that
// stores a `Voter` struct for each possible address.
// stores a `Voter` struct for each possible address.
mapping(address => Voter) public voters;
mapping(address => Voter) public voters;
// A dynamically-sized array of `Proposal` structs.
// A dynamically-sized array of `Proposal` structs.
Proposal[] public proposals;
Proposal[] public proposals;
/// Create a new ballot to choose one of `proposalNames`.
/// Create a new ballot to choose one of `proposalNames`.
constructor(bytes32[] memory proposalNames) {
constructor(bytes32[] memory proposalNames) {
chairperson = msg.sender;
chairperson = msg.sender;
voters[chairperson].weight = 1;
voters[chairperson].weight = 1;
// For each of the provided proposal names,
// For each of the provided proposal names,
// create a new proposal object and add it
// create a new proposal object and add it
// to the end of the array.
// to the end of the array.
for (uint i = 0; i < proposalNames.length; i++) {
for (uint i = 0; i < proposalNames.length; i++) {
// `Proposal({...})` creates a temporary
// `Proposal({...})` creates a temporary
// Proposal object and `proposals.push(...)`
// Proposal object and `proposals.push(...)`
// appends it to the end of `proposals`.
// appends it to the end of `proposals`.
proposals.push(Proposal({
proposals.push(Proposal({
name: proposalNames[i],
name: proposalNames[i],
voteCount: 0
voteCount: 0
}));
}));
}
}
}
}
modifier voteEnded {
require(block.timestamp < startTime + 5 minutes, "Voting period ended");
_;
}
// Give `voter` the right to vote on this ballot.
// Give `voter` the right to vote on this ballot.
// May only be called by `chairperson`.
// May only be called by `chairperson`.
function giveRightToVote(address voter) external {
function giveRightToVote(address voter) external {
// If the first argument of `require` evaluates
// If the first argument of `require` evaluates
// to `false`, execution terminates and all
// to `false`, execution terminates and all
// changes to the state and to Ether balances
// changes to the state and to Ether balances
// are reverted.
// are reverted.
// This used to consume all gas in old EVM versions, but
// This used to consume all gas in old EVM versions, but
// not anymore.
// not anymore.
// It is often a good idea to use `require` to check if
// It is often a good idea to use `require` to check if
// functions are called correctly.
// functions are called correctly.
// As a second argument, you can also provide an
// As a second argument, you can also provide an
// explanation about what went wrong.
// explanation about what went wrong.
require(
require(
msg.sender == chairperson,
msg.sender == chairperson,
"Only chairperson can give right to vote."
"Only chairperson can give right to vote."
);
);
require(
require(
!voters[voter].voted,
!voters[voter].voted,
"The voter already voted."
"The voter already voted."
);
);
require(voters[voter].weight == 0);
require(voters[voter].weight == 0);
voters[voter].weight = 1;
voters[voter].weight = 1;
}
}
/// Delegate your vote to the voter `to`.
/// Delegate your vote to the voter `to`.
function delegate(address to) external {
function delegate(address to) external {
// assigns reference
// assigns reference
Voter storage sender = voters[msg.sender];
Voter storage sender = voters[msg.sender];
require(!sender.voted, "You already voted.");
require(!sender.voted, "You already voted.");
require(to != msg.sender, "Self-delegation is disallowed.");
require(to != msg.sender, "Self-delegation is disallowed.");
// Forward the delegation as long as
// Forward the delegation as long as
// `to` also delegated.
// `to` also delegated.
// In general, such loops are very dangerous,
// In general, such loops are very dangerous,
// because if they run too long, they might
// because if they run too long, they might
// need more gas than is available in a block.
// need more gas than is available in a block.
// In this case, the delegation will not be executed,
// In this case, the delegation will not be executed,
// but in other situations, such loops might
// but in other situations, such loops might
// cause a contract to get "stuck" completely.
// cause a contract to get "stuck" completely.
while (voters[to].delegate != address(0)) {
while (voters[to].delegate != address(0)) {
to = voters[to].delegate;
to = voters[to].delegate;
// We found a loop in the delegation, not allowed.
// We found a loop in the delegation, not allowed.
require(to != msg.sender, "Found loop in delegation.");
require(to != msg.sender, "Found loop in delegation.");
}
}
// Since `sender` is a reference, this
// Since `sender` is a reference, this
// modifies `voters[msg.sender].voted`
// modifies `voters[msg.sender].voted`
sender.voted = true;
sender.voted = true;
sender.delegate = to;
sender.delegate = to;
Voter storage delegate_ = voters[to];
Voter storage delegate_ = voters[to];
if (delegate_.voted) {
if (delegate_.voted) {
// If the delegate already voted,
// If the delegate already voted,
// directly add to the number of votes
// directly add to the number of votes
proposals[delegate_.vote].voteCount += sender.weight;
proposals[delegate_.vote].voteCount += sender.weight;
} else {
} else {
// If the delegate did not vote yet,
// If the delegate did not vote yet,
// add to her weight.
// add to her weight.
delegate_.weight += sender.weight;
delegate_.weight += sender.weight;
}
}
}
}
/// Give your vote (including votes delegated to you)
/// Give your vote (including votes delegated to you)
/// to proposal `proposals[proposal].name`.
/// to proposal `proposals[proposal].name`.
function vote(uint proposal) external {
function vote(uint proposal) external voteEnded {
Voter storage sender = voters[msg.sender];
Voter storage sender = voters[msg.sender];
require(sender.weight != 0, "Has no right to vote");
require(sender.weight != 0, "Has no right to vote");
require(!sender.voted, "Already voted.");
require(!sender.voted, "Already voted.");
sender.voted = true;
sender.voted = true;
sender.vote = proposal;
sender.vote = proposal;
// If `proposal` is out of the range of the array,
// If `proposal` is out of the range of the array,
// this will throw automatically and revert all
// this will throw automatically and revert all
// changes.
// changes.
proposals[proposal].voteCount += sender.weight;
proposals[proposal].voteCount += sender.weight;
}
}
/// @dev Computes the winning proposal taking all
/// @dev Computes the winning proposal taking all
/// previous votes into account.
/// previous votes into account.
function winningProposal() public view
function winningProposal() public view
returns (uint winningProposal_)
returns (uint winningProposal_)
{
{
uint winningVoteCount = 0;
uint winningVoteCount = 0;
for (uint p = 0; p < proposals.length; p++) {
for (uint p = 0; p < proposals.length; p++) {
if (proposals[p].voteCount > winningVoteCount) {
if (proposals[p].voteCount > winningVoteCount) {
winningVoteCount = proposals[p].voteCount;
winningVoteCount = proposals[p].voteCount;
winningProposal_ = p;
winningProposal_ = p;
}
}
}
}
}
}
// Calls winningProposal() function to get the index
// Calls winningProposal() function to get the index
// of the winner contained in the proposals array and then
// of the winner contained in the proposals array and then
// returns the name of the winner
// returns the name of the winner
function winnerName() external view
function winnerName() external view
returns (bytes32 winnerName_)
returns (bytes32 winnerName_)
{
{
winnerName_ = proposals[winningProposal()].name;
winnerName_ = proposals[winningProposal()].name;
}
}
}
}