📥 Query Examples

This section provides practical examples of how to query the QIE Oracle from both JavaScript (frontend/backend using ethers.js) and Solidity (on-chain smart contracts). These examples help developers easily integrate the oracle into dApps and smart contracts.

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🟨 Solidity Example

Use this example to read the latest price from the oracle inside a smart contract.

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

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

contract PriceConsumer {
    AggregatorV3Interface public priceFeed;

    constructor(address oracleAddress) {
        priceFeed = AggregatorV3Interface(oracleAddress);
    }

    function getLatestPrice() public view returns (int256) {
        (
            , // roundId
            int256 price,
            , // startedAt
            , // updatedAt
            // answeredInRound
        ) = priceFeed.latestRoundData();

        return price;
    }
}

Replace oracleAddress with the deployed address of the QIE Oracle contract on your network.

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🟦 JavaScript Example (ethers.js)

Use this example in your frontend or backend to query the oracle using ethers.js.

const { ethers } = require("ethers");

const provider = new ethers.JsonRpcProvider("<rpc_url>");

//  Price Feed contract address (example: BNB/USD on QIE Mainnet)
const priceFeedAddress = "0xYourOracleAddress"; // BNB/USD (8 decimals)

// ABI fragment to read latestRoundData
const aggregatorV3InterfaceABI = [
  {
    "inputs": [],
    "name": "latestRoundData",
    "outputs": [
      { "internalType": "uint80", "name": "roundId", "type": "uint80" },
      { "internalType": "int256", "name": "answer", "type": "int256" },
      { "internalType": "uint256", "name": "startedAt", "type": "uint256" },
      { "internalType": "uint256", "name": "updatedAt", "type": "uint256" },
      { "internalType": "uint80", "name": "answeredInRound", "type": "uint80" }
    ],
    "stateMutability": "view",
    "type": "function"
  }
];

async function getPrice() {
  const priceFeed = new ethers.Contract(priceFeedAddress, aggregatorV3InterfaceABI, provider);
  
  const roundData = await priceFeed.latestRoundData();
  const price = roundData.answer;

  // Normalize 8 decimals
  const normalizedPrice = Number(price) / 1e8;

  console.log(`BNB/USD Price: $${normalizedPrice}`);
}

getPrice().catch(console.error);

⚠️ Don’t forget to replace 0xYourOracleAddress and your_rpc_url with the correct values for your deployment.

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📌 Additional Query: Get Historical Data

You can also query a specific round by ID to fetch past data.

Solidity:

function getHistoricalPrice(uint80 roundId) public view returns (int256) {
    (
        , 
        int256 price,
        , 
        , 
    ) = priceFeed.getRoundData(roundId);
    return price;
}

JavaScript:

async function fetchHistoricalPrice(roundId) {
  const [ , price ] = await priceFeed.getRoundData(roundId);
  const decimals = await priceFeed.decimals();

  const normalizedPrice = Number(price) / (10 ** decimals);
  console.log(`Price at round ${roundId}: ${normalizedPrice}`);
}

🧪 Tip: Mocking in Local Development

For local testing, you can deploy your own instance of the AggregatorV3 contract and call updateAnswer(int256) to simulate real-world updates.