Anybody knows why Chainlink's PriceFeed return price value with "int" type while price should always = 0?

Question

The code for get latest price in PriceFeed is:


pragma solidity ^0.6.7;

import "@chainlink/contracts/src/v0.6/interfaces/AggregatorV3Interface.sol";

contract PriceConsumerV3 {

    AggregatorV3Interface internal priceFeed;

    /**
     * Network: Kovan
     * Aggregator: ETH/USD
     * Address: 0x9326BFA02ADD2366b30bacB125260Af641031331
     */
    constructor() public {
        priceFeed = AggregatorV3Interface(0x9326BFA02ADD2366b30bacB125260Af641031331);
    }

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

Note that within function getThePrice, the line int price, why Chainlink use int type on price? Why not just uint type? And is it possible to get negative price from Chainlink PriceFeed?

user_11969592 · Answer

The Chainlink Data Feeds use int instead of uint because some prices can be negative, like when oil futures dropped below 0.

Anybody knows why Chainlink's PriceFeed return price value with "int" type while price should always >= 0?

1 Answers