This is part of the Rails API sequence of talks. Each talk has its own repository with a reference README.
Each talk is designed to walk through the creation of a real Rails API, feature-by-feature, using "error driven development". Developers should have completed the introductory Rails API talk. This sequence ends with Rails API: Behavior-Driven Development, where error-driven-development is replaced by automated testing.
Each talk covers three domains, and therefore, three APIs. The demonstration API, developed by consultants, is followed by a code-along API, in which developers and consultants work together to build the API. Finally, developers are expected to build their own API as part of the laboratory portions of each talk.
These API repositories contain a few important branches:
mastercontains starter code.solutioncontains a feature-complete reference API. History is not canonical.tutorialcontains detailed commit history, and tags for where each talk should end.
By the end of this lesson, students should be able to:
- Follow along in the creation of an API.
- Build a complete server side API in Rails
- Create a model with full CRUD capability
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Follow preparation instructions in Library API
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Follow preparation instructions in Clinic API
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Follow preparation instructions in Cookbook API
This is intended for developers to follow along as I build a library API. You may follow along as I code but I will not slow down or share this code. Later in this training we will have a code along.
Status checks will be frequent. As developers we want to be meticulous and make sure we're getting errors where expected as we build our API.
This is called "error-driven development". The goal is to see an error, and to learn what error to expect. Embrace the errors, and they will tell you what your next task is.
We'll trigger errors by issuing curl requests.
We're making a library API Right? Let's try checking to see if there are any
books by navigating to localhost:4741/books
You should get an error similar to the following:
Routing Error
No route matches [GET] "/books"Whoops! We haven't made any routes yet!
As you learned in the previous lesson, a route indicates which controller action will be triggered when a particular type of HTTP request arrives at a given URL.
In order for our API to respond to GET requests at the /books URL, we'll need
to create a Route that specifies what to do when that type of request comes in.
Add the following code to config/routes.rb:
get '/books', to: 'books#index'This tells Rails, "When you receive a GET request at the URL path /books,
invoke the index method specified in the BooksController class."
We changed a small bit of code, let's see if anything has changed.
It looks like our error has changed to:
>> uninitialized constant BooksControllerWe haven't defined a BooksController class yet, so if we try to access
localhost:4741/books, we'll get another error:
The purpose of a controller is to handle requests of some particular type. In
this case, we want to create a new controller called BooksController for
responding to requests about a resource called 'Books'.
Rails has a number of generator tools for creating boilerplate files very
quickly. To spin up a new controller, we can just run rails g controller books --skip-template-engine.
This will automatically create a new file in app/controllers called
books_controller.rb, with the following content:
class BooksController < ApplicationController
endNot all controllers handle CRUD, but those that do tend to follow the following convention for their routes and controller actions:
| Action | What It Does | HTTP Verb | URL |
|---|---|---|---|
| index | Return a list of all resource instances. | GET | /books |
| create | Create a new instance of a resource. | POST | /books |
| show | Return a single instance of a resource. | GET | /books/:id |
| update | Update a single instance of a resource. | PATCH | /books/:id |
| destroy | Destroy a single instance of a resource. | DELETE | /books/:id |
Let's add an index method to BooksController.
class BooksController < ApplicationController
def index
@books = Book.all
render json: @books
end
endLet's make a request and see if our error message has changed.
It seems we have an uninitialized constant! This is because we have yet to
tell rails what a book is, it doesn't know how to model the data.
Let's generate a model by entering bin/rails generate model Book title:string author:string
Never blindly accept generated code. Always inspect it.
Let's check out server and see if our error message has changed.
It seems we have to migrate, let's do that.
Run bin/rake db:migrate in the root of this books directory.
Let's see if our error has changed.
We can see what appears to be JSON, but there are no books! That's because we have not added any.
First let's enter our rails console so we can make use of our models. This
lets us interact with Rails from the command line.
We're going to create a single book:
Book.create([{ title: 'Less Funny Than Jason', author: 'Lauren Fazah'}])We can even use other methods such as .new and .save.
Now navigate to localhost:4741/books and see if anything has changed.
If want to use Active Record for seeing what is in our data store we can do so by looking for a speific field.
Book.find_by(author: 'Lauren Fazah')
# returns the first author
Book.where(author: 'Lauren Fazah')
# returns all results where author == 'Lauren Fazah'
Book.last
# returns the last book in the collectionThere are more ways to read and organize the data using Active Record. I would encourge you to look up more in your off time.
Let's update one of our books using Active record
book = Book.find_by(title: 'Less Funny Than Jason')
book.update(title: 'Less overall cool factor than Jason: The Sequel')
# You could also string this together
Book.find_by(title: 'Less overall cool factor than Jason: The Sequel').update(title: 'JASON IS AWESOME THE TRILOGY')Now navigate to localhost:4741/books and see if anything has changed.
Finally, if we want to remove a book with Active Record we simply do:
Book.find_by(author: 'Jason Weeks').destroyNote: find_by will only destroy one book. If we want to destroy all the
books by Jason, we have to use where.
Now navigate to localhost:4741/books and see if anything has changed.
Let's load example data by running bin/rake db:examples. It's a good idea to
write example data so you can test your own APIs.
- Be meticulous, did you check your pluralization? is your spelling correct?
Did you miss and
end? - Test frequently, check for errors in your browser and server.
- Follow your errors, they typically give you a line number, be patient. You should be able to identity the exact line of your bug before you ask for assistance.
- Remember to use the generators to your advantage. They can save you valuable time.
Developers should run these often!
bin/rake routeslists the endpoints available in your API.bin/rake testruns automated tests.bin/rails consoleopens a REPL that pre-loads the API.bin/rails dbopens your database client and loads the correct database.bin/rails serverstarts the API.scripts/*.shrun variouscurlcommands to test the API. See below.
- All content is licensed under a CCBYNCSA 4.0 license.
- All software code is licensed under GNU GPLv3. For commercial use or alternative licensing, please contact legal@ga.co.