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Intro to APIs

What is an API?

Read through these articles to get a sense of what an api is:

Then, watch this video: https://www.youtube.com/watch?v=s7wmiS2mSXY

APIs

At a very high level, APIs are rules that applications use to communicate with each other.

We are focused on building Web applications, so we are mostly concerned with Web Based APIs. These types of APIs are so common that this is what most people are talking about when referring to an "API". Since web apps communicate in HTTP, an API can be more specifically thought of as the format of HTTP requests an application accepts, and the format of data it returns. You already know about HTTP requests from Mod 2, so let's talk about how an API might return data.

JSON

So far, you have built applications for humans to view, so you've been outputting css and html that a web browser can render in a readable way.

When designing an API, you are building it for other applications to read, so you need a machine-readable way to transmit data. Typically, machine-readable formats have been just that—machine-readable (Think zeros and ones).

JSON is that format. At its core, JSON is an agreed upon format to represent data. It strikes a balance between being machine-readable, but also human-readable. It is frequently used as a language-neutral means to transmit data on the web.

Take a look at some examples. What do you notice?

That's right! It looks just like a hash!

Tip: Installing the chrome extension JSON Formatter is very helpful when viewing JSON in Google Chrome. It will format the JSON in a much more readable way.

APIs in Action

"I want to see some code!" - you, right now

Here you go! Make a new ruby file and paste this code in, replacing <your github username> with your github username.

require 'faraday'
require 'pry'
require 'json'

response = Faraday.get 'https://api.github.com/users/<your github username>'

body = response.body

binding.pry

Run the code. If you get an error that the faraday gem is missing, run gem install faraday. If you get a Bad URI error, double check your github username spelling. It has to be an actual github user.

The Faraday gem allows us to send HTTP requests from our code. We will use it a lot in Mod 3.

When you hit the pry, check out what the response and body variables are holding. Notice that the body contains that JSON format we talked about. What type of object is it?

That's right, it's a string! Wait, didn't we read about JSON being super flexible and easy to work with? A giant string doesn't seem that flexible or easy to work with :(

You're right again. Luckily, Ruby comes with a super handy library called JSON that we can use to parse this data.

Run this code in your pry session:

JSON.parse(body)

BOOM! A hash! Huzzah! We know how to work with hashes! Right? Right.

Give it a try. Using this data:

  • find your number of followers
  • find the date you joined GitHub

Congratulations! You just consumed an API.

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