pull_request_template.md

======= Instructions =======

The site uses Gray Matter for simple post markdown. Your post must comply to the markdown format. An example is below.

1. Create a new file in the _posts folder. Each file is a new post rendered on the website.
2. Test it locally :)
3. Submit a PR with only the new file in the _posts directory.

For valid examples, look at the files in this directory: https://github.com/bryanjowers/usechainlinkfunctions/tree/main/_posts

======= Everything below this line is a valid example for a new post =======

---

title: 'Price data from multiple sources' summary: 'Retrieve the price of an asset from multiple API sources. Assets could be practially anything, incuding equities, crypto, or commodities. This example pulles from multiple different data providers (APIs) and derrives the median to return on chain via Chainlink Functions.' date: '2023-03-02' author: name: Justin K

// https://github.com/justinkaseman/hardhat-starter-kit/blob/feat/ocr2dr-billing-tooling/on-demand-request-source.js

const coinMarketCapCoinId = args[0]; const coinGeckoCoinId = args[1]; const coinPaprikaCoinId = args[2]; const badApiCoinId = args[3];

const scalingFactor = parseInt(args[4]);

if (!secrets.apiKey) { throw Error('API_KEY environment variable not set for CoinMarketCap API. Get a free key from https://coinmarketcap.com/api/') }

// OCR2DR.makeHttpRequest function parameters: // - url // - method (optional, defaults to 'GET') // - headers: headers supplied as an object (optional) // - params: URL query parameters supplied as an object (optional) // - data: request body supplied as an object (optional) // - timeout: maximum request duration in ms (optional, defaults to 10000ms) // - responseType: expected response type (optional, defaults to 'json')

// Use multiple APIs & aggregate the results to enhance decentralization const coinMarketCapResponse = await OCR2DR.makeHttpRequest({ url: https://pro-api.coinmarketcap.com/v1/cryptocurrency/quotes/latest?convert=USD&id=${coinMarketCapCoinId}, // Get a free API key from https://coinmarketcap.com/api/ headers: { 'X-CMC_PRO_API_KEY': secrets.apiKey } }); const coinGeckoResponse = await OCR2DR.makeHttpRequest({ url: https://api.coingecko.com/api/v3/simple/price?ids=${coinGeckoCoinId}&vs_currencies=usd, }); const coinPaprikaResponse = await OCR2DR.makeHttpRequest({ url: https://api.coinpaprika.com/v1/tickers/${coinPaprikaCoinId} }); const badApiResponse = await OCR2DR.makeHttpRequest({ url: https://badapi.com/price/symbol/${badApiCoinId} });

const prices = [];

if (!coinMarketCapResponse.error) { prices.push(coinMarketCapResponse.data.data[coinMarketCapCoinId].quote.USD.price); } else { console.log('CoinMarketCap Error'); console.log({ ...coinMarketCapResponse }); } if (!coinGeckoResponse.error) { prices.push(coinGeckoResponse.data[coinGeckoCoinId].usd); } else { console.log('CoinGecko Error'); console.log({ ...coinGeckoResponse }); } if (!coinPaprikaResponse.error) { prices.push(coinPaprikaResponse.data.quotes.USD.price); } else { console.log('CoinPaprika Error'); console.log({ ...coinPaprikaResponse }); }

// A single failed API request does not cause the whole request to fail if (!badApiResponse.error) { prices.push(httpResponses[3].data.price.usd); } else { console.log('Bad API request failed. (This message is expected and just for demonstration purposes.)') }

// At least 3 prices are needed to aggregate the median price if (prices.length < 3) { // If an error is thrown, it will be returned back to the smart contract throw Error('More than 1 API failed'); }

const medianPrice = prices.sort((a, b) => a - b)[Math.round(prices.length / 2)]; console.log(Median Bitcoin price: $${medianPrice.toFixed(2)});

// Use the following functions to encode a single value: // - OCR2DR.encodeUint256 // - OCR2DR.encodeInt256 // - OCR2DR.encodeString // Or return a Buffer for a custom byte encoding return OCR2DR.encodeUint256(Math.round(medianPrice * 100));