How to use Chainlink AggregatorV3Interface with UUPSUpgradeable?

Question

Will Chainlink's AggregatorV3Interface.sol work with an OpenZeppelin upgradable contract? Do I place the

"priceFeed = AggregatorV3Interface(0x9326BFA02ADD2366b30bacB125260Af641031331);"

inside the "initializer{}"?

I would like the address "0x9326BFA02ADD2366b30bacB125260Af641031331" to be upgradable in the next version of the smart contract.

Is there already a way to do so?

Thank you!

Motivation & Justification
I hope that it makes sense to want to "getLatestPrice()" within the smart contract of a new token. Before deployment, there is no way of knowing the new token's address. I would like to change the address using the OpenZeppelin upgradable contract under the UUPS proxy pattern.

Is there any example online to update

priceFeed = AggregatorV3Interface(0x9326BFA02ADD2366b30bacB125260Af641031331); // Kovan Testnet

on version 2 of the smart contract?

Thank you!

Important Links:
OpenZeppelin Contracts Wizard
get-the-latest-price using Chainlink's AggregatorV3Interface
Deploying an UUPS Upgradable Contract

I have no idea how to work on version 2 of an UUPS Upgradable Contract.

This is where I got stuck using Chainlink's AggregatorV3Interface.sol with every feature selected on OpenZeppelin Contracts Wizard:

// SPDX-License-Identifier: MIT pragma solidity ^0.8.4;

import "./@openzeppelin/contracts-upgradeable/token/ERC20/ERC20Upgradeable.sol"; import "./@openzeppelin/contracts- upgradeable/token/ERC20/extensions/ERC20BurnableUpgradeable.sol"; import "./@openzeppelin/contracts- upgradeable/token/ERC20/extensions/ERC20SnapshotUpgradeable.sol"; import "./@openzeppelin/contracts-upgradeable/access/OwnableUpgradeable.sol"; import "./@openzeppelin/contracts-upgradeable/security/PausableUpgradeable.sol"; import "./@openzeppelin/contracts-upgradeable/token/ERC20/extensions/draft- ERC20PermitUpgradeable.sol"; import "./@openzeppelin/contracts- upgradeable/token/ERC20/extensions/ERC20VotesUpgradeable.sol"; import "./@openzeppelin/contracts- upgradeable/token/ERC20/extensions/ERC20FlashMintUpgradeable.sol"; import "./@openzeppelin/contracts-upgradeable/proxy/utils/Initializable.sol"; import "./@openzeppelin/contracts-upgradeable/proxy/utils/UUPSUpgradeable.sol";

import "@chainlink/contracts/src/v0.8/interfaces/AggregatorV3Interface.sol";

contract UpToken is Initializable, ERC20Upgradeable, ERC20BurnableUpgradeable, ERC20SnapshotUpgradeable, OwnableUpgradeable, PausableUpgradeable, ERC20PermitUpgradeable, ERC20VotesUpgradeable, ERC20FlashMintUpgradeable, UUPSUpgradeable { /// @custom:oz-upgrades-unsafe-allow constructor AggregatorV3Interface internal priceFeed; constructor() initializer {

priceFeed = AggregatorV3Interface(0x9326BFA02ADD2366b30bacB125260Af641031331); //

Kovan Testnet }

function initialize() initializer public { __ERC20_init("UpToken", "UPT"); __ERC20Burnable_init(); __ERC20Snapshot_init(); __Ownable_init(); __Pausable_init(); __ERC20Permit_init("UpToken"); __ERC20FlashMint_init(); __UUPSUpgradeable_init(); }

function snapshot() public onlyOwner { _snapshot(); }

function pause() public onlyOwner { _pause(); }

function unpause() public onlyOwner { _unpause(); }

function mint(address to, uint256 amount) public onlyOwner { _mint(to, amount); }

function _beforeTokenTransfer(address from, address to, uint256 amount) internal whenNotPaused override(ERC20Upgradeable, ERC20SnapshotUpgradeable) { super._beforeTokenTransfer(from, to, amount); }

function _authorizeUpgrade(address newImplementation) internal onlyOwner override {}

// The following functions are overrides required by Solidity.

function _afterTokenTransfer(address from, address to, uint256 amount) internal override(ERC20Upgradeable, ERC20VotesUpgradeable) { super._afterTokenTransfer(from, to, amount); }

function _mint(address to, uint256 amount) internal override(ERC20Upgradeable, ERC20VotesUpgradeable) { super._mint(to, amount); }

function _burn(address account, uint256 amount) internal override(ERC20Upgradeable, ERC20VotesUpgradeable) { super._burn(account, amount); }

function getLatestPrice() public view returns (int) { ( /uint80 roundID/, int price, /uint startedAt/, /uint timeStamp/, /uint80 answeredInRound/ ) = priceFeed.latestRoundData(); return price; }

}

Answer 1

Recommend you use hardhat with the upgrades plugin (https://docs.openzeppelin.com/contracts/4.x/upgradeable) to achieve this. When you deploy it the first time using hardhat, it will deploy the proxy, the implementation contract (i.e. your token contract) and an admin contract.

See 20:23 onwards in this video: https://www.youtube.com/watch?v=bdXJmWajZRY&t=15s . In fact maybe watch that entire video to get a sense of how to use hardhat with OZ upgradeable contracts.

Then when you get your token contract address, update the token contract as V2, add the contract address as a state variable and (optionally) add a setter function that gives you the ability to update that state variable in future, and deploy V2. You can see how to deploy V2 in that same video I linked above, at [24:30] or so.