Chainlink reference data contracts are on-chain reference points for external data that can be widely relied on across a smart contract network. These contracts are updated on a regular basis by multiple Chainlink nodes. This page will teach you how to make use of them.
In order to make it easy to use the reference data contracts, you can import Chainlink NPM package into your Solidity project.
Also see Create a Chainlinked Project for additional ways to use Chainlink contracts in your project.
Import the AggregatorInterface.sol contract into the source of the contract you want to consume reference data.
import "chainlink/contracts/interfaces/AggregatorInterface.sol";Set the address of the reference contract that contains the reference data you wish to consume.
AggregatorInterface ethReference;
function setReferenceContract(address _aggregator)
public
onlyOwner()
{
ethReference = AggregatorInterface(_aggregator);
}AggregatorInterface ethReference;
constructor(address _aggregator) public {
ethReference = AggregatorInterface(_aggregator);
}Now that your contract is pointing towards a reference contract, you're ready to consume the data.
function getLatestEthPrice() public view returns (int256) {
return ethReference.currentAnswer();
}You can also check the block height at which the reference data was last updated.
function getLatestUpdateHeight() public view returns (uint256) {
return ethReference.updatedHeight();
}Below is a brief but complete example of a consuming contract of Chainlink reference data.
pragma solidity 0.4.24;
import "chainlink/contracts/interfaces/AggregatorInterface.sol";
import "openzeppelin-solidity/contracts/ownership/Ownable.sol";
contract ReferenceConsumer is Ownable {
AggregatorInterface ethReference;
constructor(address _aggregator) public {
ethReference = AggregatorInterface(_aggregator);
}
function getLatestEthPrice() public view returns (int256) {
return ethReference.currentAnswer();
}
function getLatestUpdateHeight() public view returns (uint256) {
return ethReference.updatedHeight();
}
}Below are the available reference data contracts by their pairing and the address which the data is available. You can point the AggregatorInterface to any address below in order to retrieve the latest reference data on Ethereum mainnet.
ETH/USD
0x79fEbF6B9F76853EDBcBc913e6aAE8232cFB9De9