smartcontractkit / truffle-starter-kit

An example smart contract utilizing Chainlink

• Chainlink Truffle Starter Kit
• Getting Started
• It's recommended that you've gone through the Truffle getting started documentation before proceeding here.
  • Requirements
  • Quickstart
• Usage
  • Deploying Contracts
  • Run a Local Network
  • Using a Testnet or Live Network (like Mainnet or Polygon)
    • Sepolia Ethereum Testnet Setup
• Test
• Interacting with Deployed Contracts
  • Chainlink Price Feeds
  • Request & Receive Data
  • VRF Get a random number
  • Keepers
  • Verify on Etherscan
• Contributing
• Thank You!
  • Resources

Chainlink Truffle Starter Kit

Implementation of the following 4 Chainlink features using the Truffle development environment:

• Chainlink Price Feeds
• Chainlink VRF
• Chainlink Keepers
• Request & Receive data

Getting Started

It's recommended that you've gone through the Truffle getting started documentation before proceeding here.

Requirements

• 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 --versionand 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

If you're familiar with npx and npm instead of yarn, you can use npx for execution and npm for installing dependencies.

Quickstart

1. Clone and install dependencies

After installing all the requirements, run the following:

git clone https://github.com/smartcontractkit/truffle-starter-kit/
cd truffle-starter-kit

Then:

yarn

or

npm i

2. You can now do stuff!

Run truffle test

This will run your JavaScript, TypeScript, and Solidity tests underneath the ./test folder. If the development network is not specified in your truffle-config, truffle test will automatically bring up and tear down a local network on localhost:8545.

Usage

If you run truffle --help you'll get an output of all the tasks you can run.

Deploying Contracts

In your truffle-config.js you'll see section like:

  networks: {

This section of the file is where you define which networks you want to interact with. You can read more about that whole file in the Truffle documentation.. To deploy a contract, you would call:

truffle migrate --network <NETWORK>

This will deploy your contracts to the network you specify. If you do not specify network, by default truffle migrate will deploy to the development network if it is defined in your truffle-config.

If you'd like to interact with your deployed contracts, skip down to Interacting with Deployed Contracts.

Run a Local Network

One of the best ways to test and interact with smart contracts is with a local network. To start a local network with all your contracts in it, run the following:

ganache -d

This will start ganache, a local blockchain with private keys, pre-funded wallets, and an endpoint to potentially add to an EVM wallet. -d specifies a deterministic wallet. You can see all other ways you can configure Ganache here.

In our truffle-config, we've defined the local ganache network. To migrate, simply call:

truffle migrate --network ganache

Using a Testnet or Live Network (like Mainnet or Polygon)

To interact with a live or test network, you will need ETH and LINK token by following these steps:

1. Get some Sepolia Testnet ETH and LINK

Head over to the Chainlink faucets and get some ETH and LINK. Please follow the chainlink documentation if unfamiliar.

4. Create VRF V2 subscription

Head over to VRF Subscription Page and create the new subscription. Save your subscription ID and place it in your helper-truffle-config.js under subId.

Truffle Dashboard

This is our recommended way of deploying your contracts. With Truffle dashboard, you can deploy contracts and sign transactions through MetaMask - so you never exposing your private key! To do so, run:

truffle dashboard

This should bring up the dashboard on localhost:24012, where you can connect your wallet to the network of your choice. Note that if you want to deploy to a testnet or mainnet, you'll need ETH to pay the gas fees. Then, if you want to migrate your contracts, simply call:

truffle migrate --network dashboard

You should then see prompts to sign the transactions on the dashboard view. Check out this video on how to use it with Truffle and HardHat here.

Environment configuration

In some cases, you might want your transactions to be automatically signed. In which case, you will need to provide your wallet's private key

1. An RPC URL
2. A private key
3. ETH & LINK token (either testnet or real)

Let's look at an example of setting these up using the Sepolia testnet.

Sepolia Ethereum Testnet Setup

First, we will need to set environment variables. We can do so by setting them in our .env file (create it if it's not there). You can also read more about environment variables from the linked twilio blog. You'll find a sample of what this file will look like in .env.example

IMPORTANT: MAKE SURE YOU'D DONT EXPOSE THE KEYS YOU PUT IN THIS .env FILE. By that, I mean don't push them to a public repo, and please try to keep them keys you use in development not associated with any real funds.

1. Set your SEPOLIA_RPC_URL environment variable.

You can get one for free from Infura, Alchemy, or Moralis. This is your connection to the blockchain.

2. Set your PRIVATE_KEY environment variable.

This is your private key from your wallet, ie MetaMask. This is needed for deploying contracts to public networks.

WARNING

When developing, it's best practice to use a Metamask that isn't associated with any real money. A good way to do this is to use Truffle Dashboard. Alternatively, make a new browser profile (on Chrome, Brave, Firefox, etc) and install Metamask on that brower, and never send this wallet money.

Don't commit and push any changes to .env files that may contain sensitive information, such as a private key! If this information reaches a public GitHub repository, someone can use it to check if you have any Mainnet funds in that wallet address, and steal them!

.env example:

SEPOLIA_RPC_URL='https://sepolia.infura.io/v3/asdfasdfasdfasdf'
PRIVATE_KEY='abcdef'

bash example

export SEPOLIA_RPC_URL='https://sepolia.infura.io/v3/asdfasdfasdfasdf'
export PRIVATE_KEY='abcdef'

For other networks like mainnet and polygon, you can use different environment variables for your RPC URL and your private key. See the truffle-config.js to learn more.

Uncomment the sepolia network in your truffle-config. You should now be all setup! You can run any command and just pass the --network sepolia now!

To deploy all contracts:

truffle migrate --network sepolia

Test

Tests are located in the test directory, and are split between unit tests and staging/testnet tests. Unit tests should only be run on local environments, and staging tests should only run on live environments.

To run unit tests:

truffle test

Interacting with Deployed Contracts

After deploying your contracts, the deployment output will give you the contract addresses as they are deployed. You can then use these contract addresses in conjunction with Truffle scripts to perform operations on each contract. Alternatively, if you want to interact with contracts on the fly, you can read about how to use truffle console or truffle develop here.

Chainlink Price Feeds

The Price Feeds consumer contract has one script, to read the latest price of a specified price feed contract.

You can deploy just the price feed consumer with:

truffle migrate --f 3 --to 3 --network <NETWORK>

After deployment, run the following:

truffle exec scripts/readPriceConsumer.js --network <NETWORK>

Request & Receive Data

The API Consumer contract has one script, to request data from the API and wait for a response.

You can deploy just the API Consumer with:

truffle migrate --f 4 --to 4 --network <NETWORK>

After deployment, run the following:

yarn truffle exec scripts/requestAndReadAPI.js --network <NETWORK>

VRF Get a random number

The VRF Consumer contract has one script, to request a random number and wait for a response.

You can deploy just the VRF Consumer with:

truffle deploy --f 5 --to 5 --network <NETWORK>

After deployment, you'll need to add your contract address to your subscription. Head over to vrf.chain.link and add your consumer.

Then, run the following:

truffle exec scripts/requestAndReadRandomNumber.js --network <NETWORK>

Keepers

The Keepers Consumer contract has one script, to check the upkeep. After deployment, run the following:

truffle exec scripts/checkUpkeep.js --network <NETWORK>

To see everything in action, you'll want to set up a consumer at keepers.chain.link.

Verify on Etherscan

You'll need an ETHERSCAN_API_KEY environment variable. You can get one from the Etherscan API site.. If you have it set, your deploy script will try to verify them by default, but if you want to verify any manually, you can run:

truffle run verify <CONTRACT> --network <NETWORK>

example:

truffle run verify PriceConsumerV3 --network sepolia

Contributing

Contributions are always welcome! Open a PR or an issue!

Thank You!

Resources

• Chainlink Documentation
• Truffle Documentation