Voting Smart Contract

This repository contains code for a voting smart contract that allows users to create a poll and vote on it. The smart contract is written using ink!. ink! smart contracts are written in Rust and are compiled to WebAssembly before being deployed on the blockchain.

Getting Started

Prerequisites

Before you can run the smart contract, you need to install all the prerequisites for running substrate. You can find the detailed instructions for installing the prerequisites here.

In addition to the substrate prerequisites, you also need to install ink! CLI. You can find the detailed instructions here.

For building and running different components, you need to install the just and jql.

Note that just and jql are not required for running the dapp. You can alternatively run the individual commands manually. However, just and jql make it easier to run these commands.

Building

To build all the components, run the following command:

just build

Note that this might take some time if you're building the substrate node for the first time.

Testing

To run the tests for all the components, run the following command:

just test

Running

To run a local substrate node, run the following command:

just run-substrate-node

In a separate terminal, run the following command to deploy the smart contract on the local substrate node:

just deploy-voting-contract

Troubleshooting

If you get an error while deploying the smart contract, try purging the local substrate node before deploying the smart contract:

just purge-substrate-node

Upgrading

Voting smart contract intentionally introduces a bug where it does not compute the winner of a poll. This bug is fixed in the upgraded version of voting smart contract (to demonstrate the upgrade functionality).

To upgrade the smart contract, run the following command:

just upgrade-voting-contract

Once the smart contract is upgraded, it should correctly report the winners of all the future polls.

Usage

After running the node and deploying the smart contract, you can interact with the smart contract using https://contracts-ui.substrate.io/.

To add the smart contract to Contracts UI, select the Add New Contract tab and Use On-Chain Contract Address option on Contracts UI.

Note that Contracts UI, sometimes, does not register keyboard inputs on ID fields (e.g. poll ID, choice ID, etc.). The ID fields can be changed using up and down arrow keys.

Next, copy the deployed contract address from instantiated-voting-contract.json (which is created during deployment).

Finally, paste the contract address in the Contract Address field and follow on-screen instructions. You'll also have to upload contract's ABI which can be found in contracts/voting_contract/target/ink/voting_contract.json.

1. Creating a poll

   To create a new poll, select the createPoll function and enter the poll ID and description and call the contract.

   

   Once the poll is created, you should see the generated event in Transaction log on the UI.

2. Add a choice to poll

   To add choices to a poll, select the addChoice function and enter the poll ID, choice ID and choice description and call the contract.

   

   You can add multiple choices to a poll.

3. Start a poll

   Once all the choices are added to a poll, you can start the poll by selecting the startPoll function and entering the poll ID and calling the contract.

   

4. Vote on a poll

   To vote on a poll, select the vote function and enter the poll ID and choice ID and call the contract.

   

   Multiple users can vote on a poll but one user can only vote once. To add multiple votes, change the Caller on Contracts UI before calling the vote function again.

5. End a poll

   Once all the users have voted on a poll, you can end the poll by selecting the endPoll function and entering the poll ID and calling the contract.

   

6. Get poll results

   To get the results of a poll, select the getReport function and enter the poll ID and calling the contract. The results of the poll will be displayed in the Outcome section of the UI.

   

   Notice that the contract does not report the winner of the poll. This is because the contract has a intentional bug where it skips winner calculation. This bug is fixed in the upgraded version of the contract.

Next, you can follow the steps in Upgrading section of this document to upgrade the smart contract and then repeat the above process. This time, the contract should correctly report the winner of the poll. Note that you'll have to add a new contract to Contracts UI with the same contract address but upgraded version of the contract's ABI which can be found in contracts/upgraded_voting_contract/target/ink/upgraded_voting_contract.json.