Smart Contracts and Dapps Lecture Files

Election_basic.sol

pragma solidity ^0.4.0;

contract Election_basic {
    mapping (string => uint) votes;
    
    function vote (string candidate) public {
        votes[candidate]++;
    }
    
    function getVotes (string candidate) public view returns (uint) {
        return votes[candidate];
    }
}

Election_expires.sol

pragma solidity ^0.4.0;

contract Election_expires {
    mapping (string => uint) votes;
    uint expires;
    
    constructor () public {
        expires = now + 1 minutes;
    }
    
    function vote (string candidate) public {
        require(now < expires);
        votes[candidate]++;
    }
    
    function getVotes (string candidate) public view returns (uint) {
        require(now >= expires);
        return votes[candidate];
    }
}

Election_lecture.sol

pragma solidity ^0.4.0;

// This is the code that was written during the lecture
contract Election {
    mapping (string => uint) votes;
    mapping (address => bool) hasVoted;
    
    function vote (string candidate) {
        require(!hasVoted[msg.sender]);
        hasVoted[msg.sender] = true;
        votes[candidate] += 1;
    }
    
    function getVotes (string candidate) view returns (uint) {
        return votes[candidate];
    }
}

Election_limit_voters.sol

pragma solidity ^0.4.0;

contract Election_limit_voters {
    struct Voter {
        bool hasVoted;
        bool allowedToVote;
    }
    mapping (address => Voter) voters;
    mapping (string => uint) votes;
    address admin;
    
    constructor () public {
        admin = msg.sender;
    }
    
    function vote (string candidate) public {
        require(!voters[msg.sender].hasVoted && voters[msg.sender].allowedToVote);
        voters[msg.sender].hasVoted = true;
        votes[candidate] += 1;
    }
    
    function authorize (address voter) {
        require(msg.sender == admin);
        voters[voter].allowedToVote = true;
    }
    
    function getVotes (string candidate) public view returns (uint) {
        return votes[candidate];
    }
}

Election_limit_votes.sol

pragma solidity ^0.4.0;

contract Election_limit_votes {
    mapping (address => bool) voters;
    mapping (string => uint) votes;
    
    function vote (string candidate) public {
        require(!voters[msg.sender]);
        voters[msg.sender] = true;
        votes[candidate] += 1;
    }
    
    function getVotes (string candidate) public view returns (uint) {
        return votes[candidate];
    }
}