📂 dApp Developers

# Getting Started

Table of Contents

The DapiServer.sol (opens new window) contract serves data feeds to contracts with read access. All the related contracts can be imported from the @api3/airnode-protocol-v1 (opens new window) npm package.

# Starter Project

The starter project data-feed-reader-example (opens new window) is an example GitHub project that reads from a dAPI on the Polygon Mumbai testnet. Be sure to read through the README.md (opens new window) and some of the example code such as the DataFeedReaderExample.sol (opens new window) contract. Read through this entire page before running the starter project to better understand some of the terms and concepts mentioned. Finally follow the instruction in the README to get acquainted with reading data feeds.

# Coverage Policies

DapiServer.sol will check that the requester has a coverage policy for each dAPI it may attempt to read. See available dAPIs on the API3 Market (opens new window). During the preview period, all dAPIs on production networks have free access (limited time offer). Please go to the Request Data (opens new window) page to request dAPI access on production networks. See Chains and Contracts, which includes supported networks.

On the Polygon Mumbai testnet, developers can self-enable the use of any dAPI. During the deployment flow of your smart contract that reads a data feed, add code that self-enables the desired dAPI. The following scripts from the Starter Project detail how this is done. Please be sure to explore the starter project in its entirety.

# dAPI Names

A dAPI is a live data point associated with human readable dapiName. dAPI definitions simplify access and can return aggregated Beacon values or a single Beacon value. This is suitable where the more recent data point (meaning its set of Beacons could change as needed) is always more favorable, e.g., in the context of an asset price data feed.

Pass a dapiName, as an encoded bytes32 value, to the desired DapiServer.sol reader function that uses dapiName as its parameter. This is done to save gas when your smart contract calls a "readByName" function on DapiServer.sol.

The example below generates the encoded bytes32 value of AVAX/USD. Try encoding AVAX/USD in the ethers playground (opens new window).

// Encode the dapiName (such as AVAX/USD) to bytes32
// Yields: 0x415641582f555344000000000000000000000000000000000000000000000000

Then pass the encoded value to the functions mentioned above.

// Calling readDataFeedWithDapiName() using the DapiServer contract
(value, timestamp) =

# DapiServer Functions

# Optionally, use Beacon IDs

It is possible (as an option) to use a Beacon ID or Beacon set ID by calling readDataFeedId() and readDataFeedValueById(). Doing so is considered an advanced user flow. In practice reading with a name and reading with an ID are very different things. When you read with a name, you benefit from what the name maps to and how its value is aggregated from sourced Beacons. API3 manages dAPI name mappings to provide the best possible responses. When you read with an ID, you will always read a value directly from a Beacon or Beacon set. Also see dAPI Composition.

Last Updated: 12/20/2022, 7:23:07 AM