OpenZeppelin + Chainlink Upgradeable Contracts

pricefeedtrackerv1.sol

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.0;

import "@chainlink/contracts/src/v0.8/interfaces/AggregatorV3Interface.sol";
import "@openzeppelin/contracts-upgradeable/proxy/utils/Initializable.sol";

contract PriceFeedTracker is Initializable {
    address private admin;

    function initialize(address _admin) public initializer {
        admin = _admin;
    }

    function getAdmin() public view returns (address) {
        return admin;
    }

    /**
     * Network: Goerli
     * Aggregator: ETH/USD
     * Address: 0xD4a33860578De61DBAbDc8BFdb98FD742fA7028e
     */
    function retrievePrice() public view returns (int) {
        AggregatorV3Interface aggregator = AggregatorV3Interface(
            0xD4a33860578De61DBAbDc8BFdb98FD742fA7028e
        );
        (
            ,
            /*uint80 roundID*/
            int price, /*uint startedAt*/ /*uint timeStamp*/ /*uint80 answeredInRound*/
            ,
            ,

        ) = aggregator.latestRoundData();

        return price;
    }
}

pricefeedtrackerv2.sol

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.0;

import "@chainlink/contracts/src/v0.8/interfaces/AggregatorV3Interface.sol";
import "@openzeppelin/contracts-upgradeable/proxy/utils/Initializable.sol";

contract PriceFeedTrackerV2 is Initializable {
    address private admin;
    int public price; // TODO new storage slot

    // Emitted when the price is retrieved changes
    event PriceRetrievedFrom(address feed, int price);

    function initialize(address _admin) public initializer {
        admin = _admin;
    }

    function getAdmin() public view returns (address) {
        return admin;
    }

    // Fetches the price from the feed.
    // Note that the function is no longer a view function as it emits an event.
    function retrievePrice(address feed) public {
        require(
            feed != address(0x0),
            "PriceFeedTrackerV2: Pricefeed address must not be zero address."
        );

        AggregatorV3Interface aggregator = AggregatorV3Interface(feed);
        (
            ,
            /*uint80 roundID*/
            int _price, /*uint startedAt*/ /*uint timeStamp*/ /*uint80 answeredInRound*/
            ,
            ,

        ) = aggregator.latestRoundData();

        emit PriceRetrievedFrom(feed, _price);

        price = _price;
    }
}