# FtsoV2Interface > Primary interface for interacting with FTSOv2. > For the complete documentation index, see [llms.txt](/llms.txt). Markdown versions of documentation pages are available by appending `.md` to the page URL. Source: https://dev.flare.network/ftso/solidity-reference/FtsoV2Interface Primary interface for interacting with FTSOv2. This is a long-term support (LTS) interface, designed to ensure continuity even as underlying contracts evolve or protocols migrate to new versions. Sourced from `FtsoV2Interface.sol` on [GitHub](https://github.com/flare-foundation/flare-smart-contracts-v2/blob/main/contracts/userInterfaces/LTS/FtsoV2Interface.sol). ## Functions[](#functions "Direct link to Functions") ### getFeedById[](#getfeedbyid "Direct link to getFeedById") Returns stored data of a feed. A fee (calculated by the FeeCalculator contract) may need to be paid. ``` function getFeedById( bytes21 _feedId) external payable returns ( uint256 _value, int8 _decimals, uint64 _timestamp); ``` #### Parameters[](#parameters "Direct link to Parameters") - `_feedId`: The id of the feed. #### Returns[](#returns "Direct link to Returns") - `_value`: The value for the requested feed. - `_decimals`: The decimal places for the requested feed. - `_timestamp`: The timestamp of the last update.

Sample contract usage

Sample contract usage FTSOV2FeedById.sol ``` // SPDX-License-Identifier: MITpragma solidity >=0.8.0 <0.9.0;import {ContractRegistry} from "@flarenetwork/flare-periphery-contracts/coston2/ContractRegistry.sol";/* THIS IS A TEST IMPORT, in production use: import {FtsoV2Interface} from "@flarenetwork/flare-periphery-contracts/coston2/FtsoV2Interface.sol"; */import {TestFtsoV2Interface} from "@flarenetwork/flare-periphery-contracts/coston2/TestFtsoV2Interface.sol";/** * THIS IS AN EXAMPLE CONTRACT. * DO NOT USE THIS CODE IN PRODUCTION. */contract FtsoV2FeedConsumerById { TestFtsoV2Interface internal ftsoV2; // Example Feed ID for FLR/USD bytes21 public feedId = bytes21(0x01464c522f55534400000000000000000000000000); // FLR/USD /** * Get the current value of a specific feed by its ID. * @return _feedValue The latest price value of the feed. * @return _decimals The decimal precision of the feed value. * @return _timestamp The timestamp of the last feed update. */ function getFtsoV2FeedValueById() external payable returns (uint256 _feedValue, int8 _decimals, uint64 _timestamp) { /* THIS IS A TEST METHOD, in production use: ftsoV2 = ContractRegistry.getFtsoV2(); */ ftsoV2 = ContractRegistry.getTestFtsoV2(); /* Retrieves the latest value, decimals, and timestamp for the specified feed ID. */ return ftsoV2.getFeedById(feedId); }} ```

Sample contract usage

Sample contract usage FTSOV2FeedByIdWei.sol ``` // SPDX-License-Identifier: MITpragma solidity >=0.8.0 <0.9.0;import {ContractRegistry} from "@flarenetwork/flare-periphery-contracts/coston2/ContractRegistry.sol";/* THIS IS A TEST IMPORT, in production use: import {FtsoV2Interface} from "@flarenetwork/flare-periphery-contracts/coston2/FtsoV2Interface.sol"; */import {TestFtsoV2Interface} from "@flarenetwork/flare-periphery-contracts/coston2/TestFtsoV2Interface.sol";/** * THIS IS AN EXAMPLE CONTRACT. * DO NOT USE THIS CODE IN PRODUCTION. */contract FtsoV2FeedTracker { TestFtsoV2Interface internal ftsoV2; bytes21 public feedId = bytes21(0x01464c522f55534400000000000000000000000000); // FLR/USD // Event to track feed retrieval event FeedFetched(bytes21 feedId, uint256 valueInWei, uint64 timestamp); /** * Get the current value of a specific feed by its index, in wei. * @return _feedValue The latest price value of the feed in wei. * @return _timestamp The timestamp of the last update for the feed. */ function getFeedValueByIdWei() external payable returns (uint256 _feedValue, uint64 _timestamp) { /* THIS IS A TEST METHOD, in production use: ftsoV2 = ContractRegistry.getFtsoV2(); */ ftsoV2 = ContractRegistry.getTestFtsoV2(); // Retrieve feed value and timestamp from the FtsoV2 contract (_feedValue, _timestamp) = ftsoV2.getFeedByIdInWei(feedId); // Emit an event to log the feed retrieval emit FeedFetched(feedId, _feedValue, _timestamp); }} ```

Sample contract usage

Sample contract usage FTSOV2FeedsById.sol ``` // SPDX-License-Identifier: MITpragma solidity >=0.8.0 <0.9.0;import {ContractRegistry} from "@flarenetwork/flare-periphery-contracts/coston2/ContractRegistry.sol";/* THIS IS A TEST IMPORT, in production use: import {FtsoV2Interface} from "@flarenetwork/flare-periphery-contracts/coston2/FtsoV2Interface.sol"; */import {TestFtsoV2Interface} from "@flarenetwork/flare-periphery-contracts/coston2/TestFtsoV2Interface.sol";/** * THIS IS AN EXAMPLE CONTRACT. * DO NOT USE THIS CODE IN PRODUCTION. */contract FtsoV2FeedConsumer { TestFtsoV2Interface internal ftsoV2; // Feed IDs, see https://dev.flare.network/ftso/feeds for full list bytes21[] public feedIds = [ bytes21(0x01464c522f55534400000000000000000000000000), // FLR/USD bytes21(0x014254432f55534400000000000000000000000000), // BTC/USD bytes21(0x014554482f55534400000000000000000000000000) // ETH/USD ]; /** * Get the current value of the feeds. */ function getFtsoV2CurrentFeedValues() external returns ( uint256[] memory _feedValues, int8[] memory _decimals, uint64 _timestamp ) { /* THIS IS A TEST METHOD, in production use: ftsoV2 = ContractRegistry.getFtsoV2(); */ ftsoV2 = ContractRegistry.getTestFtsoV2(); /* Your custom feed consumption logic. In this example the values are just returned. */ return ftsoV2.getFeedsById(feedIds); }} ```

Sample contract usage

Sample contract usage FTSOV2FeedsByIdWei.sol ``` // SPDX-License-Identifier: MITpragma solidity >=0.8.0 <0.9.0;import {ContractRegistry} from "@flarenetwork/flare-periphery-contracts/coston2/ContractRegistry.sol";/* THIS IS A TEST IMPORT, in production use: import {FtsoV2Interface} from "@flarenetwork/flare-periphery-contracts/coston2/FtsoV2Interface.sol"; */import {TestFtsoV2Interface} from "@flarenetwork/flare-periphery-contracts/coston2/TestFtsoV2Interface.sol";/** * THIS IS AN EXAMPLE CONTRACT. * DO NOT USE THIS CODE IN PRODUCTION. */contract FtsoV2FeedConsumer { // Feed IDs, see https://dev.flare.network/ftso/feeds for full list bytes21[] public feedIds = [ bytes21(0x01464c522f55534400000000000000000000000000), // FLR/USD bytes21(0x014254432f55534400000000000000000000000000), // BTC/USD bytes21(0x014554482f55534400000000000000000000000000) // ETH/USD ]; // Event to log feed values retrieval event FeedValuesRetrieved( bytes21[] indexed feedIds, uint256[] values, uint64 timestamp ); /** * Get the current value of the feeds in wei. * A fee may be required for certain feeds, calculated by the FeeCalculator contract. * @param _feedIds The IDs of the feeds to retrieve values for. * @return _values The list of values for the requested feeds in wei. * @return _timestamp The timestamp of the last update. */ function getFeedsByIdInWei( bytes21[] calldata _feedIds ) external view returns (uint256[] memory _values, uint64 _timestamp) { // Ensure that the length of the feed IDs is non-zero require(_feedIds.length > 0, "No feed IDs provided"); /* THIS IS A TEST METHOD, in production use: ftsoV2 = ContractRegistry.getFtsoV2(); */ TestFtsoV2Interface ftsoV2 = ContractRegistry.getTestFtsoV2(); // Retrieve the feed values and timestamp from the FTSOv2 contract return ftsoV2.getFeedsByIdInWei(_feedIds); }} ```

[Open sample in Remix](https://remix.ethereum.org/#url=https://github.com/flare-foundation/developer-hub/blob/main/examples/developer-hub-solidity/FTSOV2FeedsByIdWei.sol&version=builtin&evmVersion=cancun&optimize=true&runs=200) ### getFtsoProtocolId[](#getftsoprotocolid "Direct link to getFtsoProtocolId") Returns the FTSO protocol id. ``` function getFtsoProtocolId() external view returns (uint256); ``` ### getSupportedFeedIds[](#getsupportedfeedids "Direct link to getSupportedFeedIds") Returns the list of currently supported (active) feed ids. To enumerate every feed id that has ever existed, combine the result with [`getFeedIdChanges`](#getfeedidchanges). ``` function getSupportedFeedIds() external view returns (bytes21[] memory _feedIds); ``` #### Returns[](#returns-4 "Direct link to Returns") - `_feedIds`: The list of supported feed ids. ### getFeedIdChanges[](#getfeedidchanges "Direct link to getFeedIdChanges") Returns the list of feed id changes (old/new pairs). ``` function getFeedIdChanges() external view returns (FeedIdChange[] memory _feedIdChanges); ``` #### Returns[](#returns-5 "Direct link to Returns") - `_feedIdChanges`: The list of changed feed id pairs. ### calculateFeeById[](#calculatefeebyid "Direct link to calculateFeeById") Calculates the fee for fetching a single feed. ``` function calculateFeeById(bytes21 _feedId) external view returns (uint256 _fee); ``` #### Parameters[](#parameters-4 "Direct link to Parameters") - `_feedId`: The id of the feed. #### Returns[](#returns-6 "Direct link to Returns") - `_fee`: The fee for fetching the feed. ### calculateFeeByIds[](#calculatefeebyids "Direct link to calculateFeeByIds") Calculates the fee for fetching multiple feeds at once. ``` function calculateFeeByIds(bytes21[] memory _feedIds) external view returns (uint256 _fee); ``` #### Parameters[](#parameters-5 "Direct link to Parameters") - `_feedIds`: The list of feed ids. #### Returns[](#returns-7 "Direct link to Returns") - `_fee`: The combined fee. ### verifyFeedData[](#verifyfeeddata "Direct link to verifyFeedData") Checks if the feed data is valid (i.e. is part of the confirmed Merkle tree). ``` function verifyFeedData( struct FtsoV2Interface.FeedDataWithProof _feedData) external view returns ( bool); ``` #### Parameters[](#parameters-6 "Direct link to Parameters") - `_feedData`: Structure containing data about the feed (FeedData structure) and Merkle proof. #### Returns[](#returns-8 "Direct link to Returns") - `_0`: true if the feed data is valid.

Sample contract usage

Sample contract usage FTSOV2AnchorConsumer.sol ``` // SPDX-License-Identifier: MITpragma solidity >=0.8.0 <0.9.0;import {FtsoV2Interface} from "@flarenetwork/flare-periphery-contracts/coston2/FtsoV2Interface.sol";import {ContractRegistry} from "@flarenetwork/flare-periphery-contracts/coston2/ContractRegistry.sol";import {TestFtsoV2Interface} from "@flarenetwork/flare-periphery-contracts/coston2/TestFtsoV2Interface.sol";/** * THIS IS AN EXAMPLE CONTRACT. * DO NOT USE THIS CODE IN PRODUCTION. */contract FtsoV2AnchorFeedConsumer { bytes21 private constant FLR_USD_ID = 0x01464c522f55534400000000000000000000000000; bytes21 private constant BTC_USD_ID = 0x014254432f55534400000000000000000000000000; bytes21 private constant ETH_USD_ID = 0x014554482f55534400000000000000000000000000; mapping(uint32 => mapping(bytes21 => TestFtsoV2Interface.FeedData)) public provenFeeds; // Track which feeds have been proven per round for easy enumeration mapping(uint32 => bytes21[]) private _provenFeedIdsByRound; mapping(uint32 => mapping(bytes21 => bool)) private _isProven; event FeedProven( uint32 indexed votingRoundId, bytes21 indexed id, int32 value, uint16 turnoutBIPS, int8 decimals ); function savePrice( TestFtsoV2Interface.FeedDataWithProof calldata data ) external { /* THIS IS A TEST METHOD, in production use: ftsoV2 = ContractRegistry.getFtsoV2(); */ TestFtsoV2Interface ftsoV2 = ContractRegistry.getTestFtsoV2(); // Step 1: Verify the proof require(ftsoV2.verifyFeedData(data), "Invalid proof"); // Step 2: Ensure the proof is for the desired feedId to avoid manipulation require( data.body.id == FLR_USD_ID || data.body.id == BTC_USD_ID || data.body.id == ETH_USD_ID, "Proof is not for desired feedId" ); // Step 3: Use the feed data with app specific logic // Here the feed data is saved uint32 roundId = data.body.votingRoundId; bytes21 id = data.body.id; provenFeeds[roundId][id] = data.body; // Record id for enumeration if first time proven in this round if (!_isProven[roundId][id]) { _isProven[roundId][id] = true; _provenFeedIdsByRound[roundId].push(id); } emit FeedProven( roundId, id, data.body.value, data.body.turnoutBIPS, data.body.decimals ); } // Returns whether a given feed id has been proven for the round function isProven( uint32 votingRoundId, bytes21 id ) external view returns (bool) { return _isProven[votingRoundId][id]; } // Returns all feed ids proven for a voting round function getProvenFeedIds( uint32 votingRoundId ) external view returns (bytes21[] memory) { return _provenFeedIdsByRound[votingRoundId]; } // Returns all proven feeds (full FeedData) for a voting round function getProvenFeeds( uint32 votingRoundId ) external view returns (TestFtsoV2Interface.FeedData[] memory) { bytes21[] memory ids = _provenFeedIdsByRound[votingRoundId]; TestFtsoV2Interface.FeedData[] memory out = new TestFtsoV2Interface.FeedData[](ids.length); for (uint256 i = 0; i < ids.length; i++) { out[i] = provenFeeds[votingRoundId][ids[i]]; } return out; }} ```