An example project for reading API3 data feeds on the Polygon testnet

API3 serves three kinds of data feeds:

• Beacon: A single-source data feed, addressed by the hash of its parameters
• Beacon set (not offered yet): Aggregation of multiple Beacons, addressed by the hash of the underlying Beacon IDs
• dAPI: A managed data feed that is pointed to a Beacon or a Beacon set, addressed by its human-readable name

All data feeds that API3 serves on a chain can be read from a single DapiServer contract using the name for dAPIs and the ID for Beacons and Beacon sets. In this repo, we inherit the DapiReader contract to implement an example data feed reader contract that reads from Beacon IDs.

Anyone can read an API3 data feed with an off-chain, static call. However, only contracts allowed by an authorized account are allowed to read on-chain. For production use-cases on mainnet, you will need to pay for contract read access. On Rsk Testnet, there is a contract that you can call to allow your contract to do on-chain reads for free for testing purposes, which we use in this repo.

Beacons and Beacon sets are read using their IDs. You can find the Beacons Ids(known as Datafeed Id) here:

  "RBTC/BTC": "0x4aaf6e2ef7fc8280aa99d321e53ef2e4f111b7805677a262eb5882b1a27b5108",
  "RBTC/USD": "0x5295f30436b2077a67c02001f62e8aabcc6688d87a8ce8db6f2b7a7cad4f0b01",
  "RIF/USD": "0x3c7ba811cb33ad3784389a580af1a657ce0ebd701b1eb415eafabe5a4885e92f",
  "

While using the scripts in this repo, you will need to specify data feed ID as the environment variable DATA_FEED_ID.

• Install dependencies

yarn

• Enter credentials

cp credentials.example.json credentials.json

# ..and populate credentials.json with your mnemonic

Use the scripts below to read the data feeds off-chain. You need to do the static call with a VoidSigner with address 0, see the scripts for details.

DATA_FEED_ID=0x5295f30436b2077a67c02001f62e8aabcc6688d87a8ce8db6f2b7a7cad4f0b01 yarn run:off-chain-read-with-id

• Get RSK Testnet tokens from the faucet

• Deploy DataFeedReaderExample

yarn deploy

First send a transaction to allow the deployed DataFeedReaderExample contract to read the data feed. Note that you only need to do this once, and you can only do this on RSK testnet.

DATA_FEED_ID=0x5295f30436b2077a67c02001f62e8aabcc6688d87a8ce8db6f2b7a7cad4f0b01 yarn run:allow-to-read-with-id

Then, you can use the script below to have the DataFeedReaderExample contract read the data feed.

DATA_FEED_ID=0x5295f30436b2077a67c02001f62e8aabcc6688d87a8ce8db6f2b7a7cad4f0b01 yarn run:read-with-id

You can also omit the timestamp and only read the value.

DATA_FEED_ID=0x5295f30436b2077a67c02001f62e8aabcc6688d87a8ce8db6f2b7a7cad4f0b01 yarn run:read-value-with-id

A MockDapiServer contract is provided for local development and testing. See the tests for its usage, and run the tests with

yarn test