This is a section of the Javascript Blockchain/Smart Contract FreeCodeCamp Course.

⌨️ (13:41:02) Lesson 9: Hardhat Smart Contract Lottery

Full Repo

• Hardhat Smartcontract Lottery (Raffle) FCC
• Getting Started
  • Requirements
  • Quickstart
  • Typescript
• Useage
  • Testing
    • Test Coverage
• Deployment to a testnet or mainnet
  • Estimate gas cost in USD
  • Verify on etherscan
    • Typescript differences
• Linting
• Thank you!

This project is apart of the Hardhat FreeCodeCamp video.

Video coming soon...

• git
  • You'll know you did it right if you can run git --version and you see a response like git version x.x.x
• Nodejs
  • You'll know you've installed nodejs right if you can run:
    • node --version and get an ouput like: vx.x.x
• Yarn instead of npm
  • You'll know you've installed yarn right if you can run:
    • yarn --version and get an output like: x.x.x
    • You might need to install it with npm or corepack

git clone https://github.com/PatrickAlphaC/hardhat-smartcontract-lottery-fcc
cd hardhat-smartcontract-lottery-fcc
yarn

If you want to get to typescript and you cloned the javascript version, just run:

git checkout typescript
yarn 

Deploy:

yarn hardhat deploy

yarn hardhat test

yarn hardhat coverage

1. Setup environment variabltes

You'll want to set your RINKEBY_RPC_URL and PRIVATE_KEY as environment variables. You can add them to a .env file, similar to what you see in .env.example.

• PRIVATE_KEY: The private key of your account (like from metamask). NOTE: FOR DEVELOPMENT, PLEASE USE A KEY THAT DOESN'T HAVE ANY REAL FUNDS ASSOCIATED WITH IT.
  • You can learn how to export it here.
• RINKEBY_RPC_URL: This is url of the rinkeby testnet node you're working with. You can get setup with one for free from Alchemy

2. Get testnet ETH

Head over to faucets.chain.link and get some tesnet ETH & LINK. You should see the ETH and LINK show up in your metamask. You can read more on setting up your wallet with LINK.

3. Setup a Chainlink VRF Subscription ID

Head over to vrf.chain.link and setup a new subscription, and get a subscriptionId. You can reuse an old subscription if you already have one.

You can follow the instructions if you get lost. You should leave this step with:

1. A subscription ID

2. Your subscription should be funded with LINK

3. Deploy

In your helper-hardhat-config.js add your subscriptionId under the section of the chainId you're using (aka, if you're deploying to rinkeby, add your subscriptionId in the subscriptionId field under the 4 section.)

Then run:

yarn hardhat deploy --network rinkeby

And copy / remember the contract address.

4. Add your contract address as a Chainlink VRF Consumer

Go back to vrf.chain.link and under your subscription add Add consumer and add your contract address. You should also fund the contract with a minimum of 1 LINK.

5. Register a Chainlink Keepers Upkeep

You can follow the documentation if you get lost.

Go to keepers.chain.link and register a new upkeep. Your UI will look something like this once completed:

6. Enter your raffle!

You're contract is now setup to be a tamper proof autonomous verifiably random lottery. Enter the lottery by running:

yarn hardhat run scripts/enter.js --network rinkeby

To get a USD estimation of gas cost, you'll need a COINMARKETCAP_API_KEY environment variable. You can get one for free from CoinMarketCap.

Then, uncomment the line coinmarketcap: COINMARKETCAP_API_KEY, in hardhat.config.js to get the USD estimation. Just note, everytime you run your tests it will use an API call, so it might make sense to have using coinmarketcap disabled until you need it. You can disable it by just commenting the line back out.

If you deploy to a testnet or mainnet, you can verify it if you get an API Key from Etherscan and set it as an environemnt variable named ETHERSCAN_API_KEY. You can pop it into your .env file as seen in the .env.example.

In it's current state, if you have your api key set, it will auto verify kovan contracts!

However, you can manual verify with:

yarn hardhat verify --constructor-args arguments.js DEPLOYED_CONTRACT_ADDRESS

1. .js files are now .ts
2. We added a bunch of typescript and typing packages to our package.json. They can be installed with:
   1. yarn add @typechain/ethers-v5 @typechain/hardhat @types/chai @types/node ts-node typechain typescript
3. The biggest one being typechain
   1. This gives your contracts static typing, meaning you'll always know exactly what functions a contract can call.
   2. This gives us factories that are specific to the contracts they are factories of. See the tests folder for a version of how this is implemented.
4. We use imports instead of require. Confusing to you? Watch this video
5. Add tsconfig.json

To check linting / code formatting:

yarn lint

or, to fix:

yarn lint:fix

If you appreciated this, feel free to follow me or donate!

ETH/Polygon/Avalanche/etc Address: 0x9680201d9c93d65a3603d2088d125e955c73BD65