Building and Using External Adapters – Chainlink Engineering Tutorials

Chainlink is an infrastructure designed to be unlimited in how customizable it can be. External adapters are open sourced packages that allows Chainlink nodes to transform and receive data however they like. With external adapters you can do:
1. API Authentication (keep private API password keys private)
2. Private, low latency, and/or high throughput off-chain computation to save gas.
3. Write data to other blockchains (interoperability).
4. Any desired functionality that isn’t covered with the core adapters
This allows your solidity smart contracts to have access to data that they never would have before.

This video goes over:
1. What an external adapter is
2. How to build one
3. Who should host it
4. How to use one

Blog post: https://blog.chain.link/build-and-use-external-adapters/

Chainlink is a decentralized oracle network that enables smart contracts to securely access off-chain data feeds, web APIs, and traditional bank payments. Chainlink is critical to connecting the blockchain ecosystem to the rest of the world.

Code setup:
Install Yarn: https://classic.yarnpkg.com/en/docs/install/
Install nodejs: https://nodejs.org/en/download/
Nodejs External Adapter Template: https://github.com/PatrickAlphaC/CL-EA-NodeJS-Template
Nodejs External Adapter Template with the completed weather API code: https://github.com/PatrickAlphaC/openweathermap_cl_ea
External adapter documentation: https://docs.chain.link/docs/external-adapters
Learn more about Environment Variables: https://www.twilio.com/blog/2017/01/how-to-set-environment-variables.html

Remix (kovan) from ending:
https://remix.ethereum.org/#version=soljson-v0.6.6+commit.6c089d02.js&optimize=false&gist=f856530b20943e92ed6cc69c1285cdfe&evmVersion=null

Important Commands/APIs:
curl -X POST -H “content-type:application/json” “http://localhost:8080/” –data ‘{ “id”: 0, “data”: { “from”: “ETH”, “to”: “USD” } }’

API:
https://min-api.cryptocompare.com/data/price?fsym=ETH&tsyms=USD

Node Listing Service:
Market.link: https://market.link/

APIs used:
OpenWeatherMap: https://openweathermap.org/
Alpha Vantage: https://www.alphavantage.co/
CryptoCompare: https://www.cryptocompare.com/

Learn more about Chainlink :
Documentation: https://docs.chain.link/docs/getting-started
Discord: https://discordapp.com/invite/aSK4zew – Very active and developer focused!
Website https://chain.link
Building DeFi Applications: https://defi.chain.link/
Twitter https://twitter.com/chainlink
Telegram https://t.me/chainlinkofficial