📝 Reading Beacon in Contract

This tutorial will guide you in having a contract read data from an active Nodary Beacon.

• We will inherit DapiReader.sol in our contract in order to be able to call the needed functions to read data from a Nodary Beacon.

• Import DapiReader.sol and inherit.

// SPDX-License-Identifier: MIT
pragma solidity 0.8.9;

import "@api3/airnode-protocol-v1/contracts/dapis/DapiReader.sol";

contract BeaconReaderExample is DapiReader {...}

• We add _dapiServer in constructor since this is where the Beacons reside.

// SPDX-License-Identifier: MIT
pragma solidity 0.8.9;

import "@api3/airnode-protocol-v1/contracts/dapis/DapiReader.sol";

contract BeaconReaderExample is DapiReader {
    constructor(address _dapiServer) DapiReader(_dapiServer) {}
    
    ...
}

• Finally, add the functions readBeaconWithId, readBeaconValueWithId and beaconIdToReaderToWhitelistStatus.

// SPDX-License-Identifier: MIT
pragma solidity 0.8.9;

import "@api3/airnode-protocol-v1/contracts/dapis/DapiReader.sol";

contract BeaconReaderExample is DapiReader {
    constructor(address _dapiServer) DapiReader(_dapiServer) {}

    function readBeaconWithId(bytes32 beaconId)
        external
        view
        returns (int224 value, uint256 timestamp)
    {
        (value, timestamp) = IDapiServer(dapiServer).readDataFeedWithId(
            beaconId
        );
    }

    function readBeaconValueWithId(bytes32 beaconId)
        external
        view
        returns (int224 value)
    {
        value = IDapiServer(dapiServer).readDataFeedValueWithId(beaconId);
    }

    function beaconIdToReaderToWhitelistStatus(
        bytes32 beaconId,
        address reader
    )
        external
        view
        returns (uint64 expirationTimestamp, uint192 indefiniteWhitelistCount)
    {
        return
            IDapiServer(dapiServer).dataFeedIdToReaderToWhitelistStatus(
                beaconId,
                reader
            );
    }

}

Function Name	What is returns
readBeaconWithId	Returns latest value and timestamp of the Beacon.
readBeaconValueWithId	Returns only the latest value of the Beacon.
beaconIdToReaderToWhitelistStatus	Returns the whitelist status of the reader address.

• Now you can do anything you want with the value you read from beacon.

...

function doSomething() {
    int224 value = readBeaconValueWithId(beaconId);
    ...
}

...

caution

Make sure to whitelist your contract after deploying it. DapiServer addresses can be found here. You can use this guide to whitelist your contract.