Building an API

Overview

• API Basics
• Review of New Tools
• Tutorial
• Share

Warmup

Take 5 minutes to use the internet to answer the following questions.

• What is an API in the context of web development?
• Why would we want to expose information in a database we control through an API?

API Basics

What is an API

• A way for applications to communicate with each other
• Code that governs the access points to the server
• Writing and Retrieving data are handled through HTTP requests to a server and don’t require a frontend.

Why create an API

• Single Page Applications - avoid full-page refresh
• Allow other developers to use our service
• Break our application into smaller applications

JSON

Review the examples linked in the lesson with a partner.

• Share your observations

Big Idea

• JSON is a machine/human readable way to transmit data.
• String representation of data.
• Most languages have libraries to create/parse JSON (basically langauge neutral).
• Rarely work with JSON directly. Instead, use familiar datatypes (hashes) and then encode as JSON.

New Tools

Creating and Parsing

• JSON.generate(some_ruby_hash)
• JSON.parse(some_json_string)

Creating a new application

• rails new my_api --api

• Configures your application to start with a more limited set of middleware than normal.
• ApplicationController inherit from ActionController::API instead of ActionController::Base.
• Configure the generators to skip generating views, helpers and assets.

Take 5 minutes to use the internet to answer the following questions.

• What areas of our codebase do we need to test in an API?
• How will our tests be different from feature tests we have implemented in the past?

Testing

• get 'api/v1/items'
• response
• JSON.parse(response)

Controller

• render
• json: Item.all

Versioning APIs

• APIs will need to be updated and improved over time
• We version APIs by namespacing the API endpoints (routes)

• For consumers the api endpoint has minimal changes and they have time to change their code to handle the new response.

• get 'api/v1/items', to: 'items#index'
• get 'api/v2/items', to: 'items#index'

Try It!

Questions?

Checks for Understanding

• What are some reasons you’d want to create an API?
• At its core, what is JSON?
• What are the main differences between creating a traditional Rails application and creating an API?