Solidity voting contract example

Example of basic implementation for a votind contract developed in Solidiy and running over the Ethereum blockchain

The voting contract has this functionalities:

• The voting has only 6 fixed options: “0” or “1” or “2” or “3” or “4” or “5”. Each nonzero option corresponds to 1 candidate (i.e., in total, there are 5 candidates). The zero option (“0”) denotes a blank vote and, thus, it cannot be associated with any candidate.

• The voting process is kept open (i.e., voting is permitted) during a certain time frame which is specified by the creator of the contract.

• The votes can come only from addresses that are marked as “authorized”. The creator of the contract must mark all permitted addresses as “authorized” before the voting can begin (write a function that would help the creator to mark an address as “authorized”).

• To prevent cheating, each verified address can vote only once - after voting, the address is marked as “unauthorized” and thus can't vote again.

• Write a function that returns the winner. In order to have a winner, two conditions should be satisfied as follows: (i) The winner should have at least the 60% of votes, and (ii) When (i) holds, the percentage of blank votes should be less or equal to 15%. Otherwise, there is no winner.

• The contract should not accept any funds sent to it. Any funds sent to the contract (e.g., by accident) should be returned to the sender.

Project structure and dependencies

1. 'contracts': Holds three contracts with different complexity level, denoted with number prefix in file name.
2. 'scripts': Holds two scripts to deploy a contract. It is explained below.
3. 'tests': Contains one test file for 'Ballot' contract with unit tests in Solidity.

Using the contract

1. Deploying the contract

2. Operate the contract