[]

Overview

Use this package to install the Fetch User Contracts and integrate Fetch into your contracts.

Once installed this will allow your contracts to inherit the functions from UsingFetch.

How to Use

Just inherit the UsingFetch contract, passing the Fetch address as a constructor argument:

Here's an example

import "usingfetch/contracts/UsingFetch.sol";

contract PriceContract is UsingFetch {

  // This contract now has access to all functions in UsingFetch
  constructor(address payable _fetchAddress) UsingFetch(_fetchAddress) {}

  function getPrice() public view returns (uint256) {
      bytes32 _plsQueryId = keccak256(abi.encode("SpotPrice", abi.encode("llpls", "usd")));

      uint256 _timestamp;
      bytes memory _value;

      (_value, _timestamp) = getDataBefore(_plsQueryId, block.timestamp);
      return abi.decode(_value,(uint256));
  }
}

Addresses:

Find Fetch contract addresses:

• mainnet: 0x23716E2dCC327429253335E4646dEbaD1Ac0E57c
• testnet: 0x252eC80dEa7F3eD0CC57e0f1112d6f56Ae9523fb

Available Fetch functions:

Children contracts have access to the following functions:

/**
 * @dev Retrieves the next value for the queryId after the specified timestamp
 * @param _queryId is the queryId to look up the value for
 * @param _timestamp after which to search for next value
 * @return _value the value retrieved
 * @return _timestampRetrieved the value's timestamp
 */
function getDataAfter(bytes32 _queryId, uint256 _timestamp)
    public
    view
    returns (bytes memory _value, uint256 _timestampRetrieved);

/**
  * @dev Retrieves the latest value for the queryId before the specified timestamp
  * @param _queryId is the queryId to look up the value for
  * @param _timestamp before which to search for latest value
  * @return _value the value retrieved
  * @return _timestampRetrieved the value's timestamp
  */
function getDataBefore(bytes32 _queryId, uint256 _timestamp)
    public
    view
    returns (bytes memory _value, uint256 _timestampRetrieved);

/**
 * @dev Retrieves next array index of data after the specified timestamp for the queryId
 * @param _queryId is the queryId to look up the index for
 * @param _timestamp is the timestamp after which to search for the next index
 * @return _found whether the index was found
 * @return _index the next index found after the specified timestamp
 */
function getIndexForDataAfter(bytes32 _queryId, uint256 _timestamp)
    public
    view
    returns (bool _found, uint256 _index);

/**
 * @dev Retrieves latest array index of data before the specified timestamp for the queryId
 * @param _queryId is the queryId to look up the index for
 * @param _timestamp is the timestamp before which to search for the latest index
 * @return _found whether the index was found
 * @return _index the latest index found before the specified timestamp
 */
function getIndexForDataBefore(bytes32 _queryId, uint256 _timestamp)
    public
    view
    returns (bool _found, uint256 _index);

/**
 * @dev Retrieves multiple uint256 values before the specified timestamp
 * @param _queryId the unique id of the data query
 * @param _timestamp the timestamp before which to search for values
 * @param _maxAge the maximum number of seconds before the _timestamp to search for values
 * @param _maxCount the maximum number of values to return
 * @return _values the values retrieved, ordered from oldest to newest
 * @return _timestamps the timestamps of the values retrieved
 */
function getMultipleValuesBefore(
  bytes32 _queryId,
  uint256 _timestamp,
  uint256 _maxAge,
  uint256 _maxCount
)
  public
  view
  returns (bytes[] memory _values, uint256[] memory _timestamps);

/**
 * @dev Counts the number of values that have been submitted for the queryId
 * @param _queryId the id to look up
 * @return uint256 count of the number of values received for the queryId
 */
function getNewValueCountbyQueryId(bytes32 _queryId)
  public
  view
  returns (uint256);

/**
 * @dev Returns the address of the reporter who submitted a value for a data ID at a specific time
 * @param _queryId is ID of the specific data feed
 * @param _timestamp is the timestamp to find a corresponding reporter for
 * @return address of the reporter who reported the value for the data ID at the given timestamp
 */
function getReporterByTimestamp(bytes32 _queryId, uint256 _timestamp)
  public
  view
  returns (address);

/**
 * @dev Gets the timestamp for the value based on their index
 * @param _queryId is the id to look up
 * @param _index is the value index to look up
 * @return uint256 timestamp
 */
function getTimestampbyQueryIdandIndex(bytes32 _queryId, uint256 _index)
  public
  view
  returns (uint256);

/**
 * @dev Determines whether a value with a given queryId and timestamp has been disputed
 * @param _queryId is the value id to look up
 * @param _timestamp is the timestamp of the value to look up
 * @return bool true if queryId/timestamp is under dispute
 */
function isInDispute(bytes32 _queryId, uint256 _timestamp)
  public
  view
  returns (bool);

/**
 * @dev Retrieve value from oracle based on queryId/timestamp
 * @param _queryId being requested
 * @param _timestamp to retrieve data/value from
 * @return bytes value for query/timestamp submitted
 */
function retrieveData(bytes32 _queryId, uint256 _timestamp)
  public
  view
  returns (bytes memory);

Fetch Playground:

For ease of use, the UsingFetch repo comes with a version of Fetch Playground for easier integration. This version contains a few helper functions:

/**
 * @dev A mock function to submit a value to be read without miners needed
 * @param _queryId The fetchId to associate the value to
 * @param _value the value for the queryId
 * @param _nonce the current value count for the query id
 * @param _queryData the data used by reporters to fulfill the data query
 */
function submitValue(bytes32 _queryId, bytes calldata _value, uint256 _nonce, bytes memory _queryData) external;

/**
 * @dev A mock function to create a dispute
 * @param _queryId The fetchId to be disputed
 * @param _timestamp the timestamp of the value to be disputed
 */
function beginDispute(bytes32 _queryId, uint256 _timestamp) external;

Test

Open a git bash terminal and run this code:

git clone https://github.com/fetchoracle/usingfetch.git
cd usingfetch
npm i
npm test

Keywords

Decentralized oracle, price oracle, oracle, Fetch, price data, smart contracts.