Reading Data

Connecting to the Oracle

To use Tellor data, import usingTellor, our helper contract for any network, connect it to the Oracle, and read a value on your queryId. This quickstart uses the BTC/USD SpotPrice as an example query.

Installation

npm install usingtellor

Importing

Just import the UsingTellor contract into your solidity file passing the desired Tellor address (see references page) as a parameter.

pragma solidity >=0.8.0;

import "usingtellor/contracts/UsingTellor.sol";

contract MyContract is UsingTellor {

  constructor(address payable _tellorAddress) UsingTellor(_tellorAddress) public {

  }

  // ...

}

Line 7: Your constructor needs to specify the Tellor contract address (see references page for the address). For testing, use a TellorPlayground address. In production, use the Oracle address on your chosen network.

Reading data

Once we've created a queryId , we're ready to add our Tellor data feed to our contract code. The best-practice for reading Tellor data is to use the function getDataBefore . We use this function to leave time for disputes. In the example below, we'll add to the snippet above a function getBtcSpotPrice() that reads the btc/usd price feed from the Oracle.

// SPDX-License-Identifier: MIT
pragma solidity 0.8.3;

import "usingtellor/contracts/UsingTellor.sol";

contract ExampleContract is UsingTellor {

    ...

    function getBtcSpotPrice() external view returns(uint256) {
    
      bytes memory _queryData = abi.encode("SpotPrice", abi.encode("btc", "usd"));
      bytes32 _queryId = keccak256(_queryData);
      
      (bool ifRetrieve, bytes memory _value, ) =
          getDataBefore(_queryId, block.timestamp - 1 hours);
      if (!ifRetrieve) return 0;
      return abi.decode(_value, (uint256));
    }

Line 16: Use usingtellor's getDataBefore(bytes32 _queryId, uint256 _timestamp) function with a buffer time (1 hour for example) to allow time for a bad value to be disputed

Addendum: Tellor Playground

Tellor Playground aims to help anyone building on Tellor to quickly bootstrap, implement, and test a Tellor integration. See the reference page for deployed addresses on various test networks.

The Playground is a simplified (and not a real oracle) Tellor, containing only the small bits that developers need to worry about: getting data, adding tips, reading events and so forth.

How to implement

Implementing the Playground is as simple as pointing the UsingTellor constructor to the Playground on your network. See the reference page for deployed addresses on various test networks.

When finished testing with the Playground, switching back to the real Tellor only requires updating the oracle address in your UsingTellor implementation.