RESTful best practices

RESTful best practices Jean-Baptiste Escoyez & Nicolas Jacobeus FOSDEM ’08 Ruby on Rails DevRoom 24 February 2008 Frailers.net

Outline REST REST in Rails REST in Rails: Best practices

REST What is REST? How does REST work? Why REST? REST

What is REST? It’s about communication between computers It’s about designing the architecture of your applications REST » What is REST?

It’s about communication between computers Web services! SOAP / XML-RPC => communication REST => communication + standardisation REST » What is REST?

It’s about architecturing your application esis by Roy Fielding (2000) “Architectural Styles and the Design of Network-based Software Architectures” REST applies some constraints to the architecture of your application e interface is the same for humans and computers (by the way: REST means Representational State Transfer... I think)‫‏‬ REST » What is REST?

How does REST work ? Everything is a “resource” 4 basic requirements for a RESTful system REST » How does REST work?

e concept of resource Resource = thing exposed by the system to the outside world Everything is a resource http://www.frailers.net/users/1 http://www.frailers.net/users/1/memberships Independent from its representation user.html => http://www.frailers.net/users/1 user.jpg => http://www.frailers.net/users/1 REST » How does REST work?

When is a system RESTful ? Addressability Statelessness Connectivity Uniform interface 4 standardized actions: GET - POST - PUT - DELETE Safety (GET) Idempotence (PUT-DELETE) REST » How does REST work?

So, why REST ? Standardisation is good Why use so many diﬀerent functions when you always do the same (CRUD’ing objects) Why separate the logic for computers and humans ? (segregation is evil) Statelessness => scalability and decoupling REST » Why REST?

Enough for this theoretical HTTP stuﬀ! is is a DevRoom about , right ? REST » Why REST?

REST in Rails (Not on Rails !)

REST in Rails Addressability: RESTful routes Representation independence: respond_to Nesting resources Developing REST clients ...and some tasty Rails sugars REST in Rails

Addressability : Routes RESTless RESTful VERB HREF VERB URI POST /users/create POST /users GET /users/1 GET /users/1 POST /users/1/update PUT /users/1 ???? /users/1/delete DELETE /users/1 REST in Rails » Routes

Addressability : Routes map.resources :users Resource Verb Action /users GET index /users POST create /users/1 GET show /users/1 PUT update /users/1 DELETE destroy REST in Rails » Routes

RESTful Rails controller A RESTful controller has 7 standard actions Each controller deals with a resource (user) and its collection (list of users) REST in Rails » Routes

Representation independence: respond_to Based on: HTTP Accept Header Format extension http://www.frailers.net/articles/24/comments/1.html http://www.frailers.net/articles/24/comments/1.js REST in Rails » respond_to

Making REST clients : ActiveResource class Project < ActiveResource::Base self.site = “http://localhost:3000” end projects = Project.find(:all) new_project = Project.new(:name => “My new project”) new_project.save REST in Rails » ActiveResource

Nested resources http://www.frailers.net/articles/24/comments/1 http://www.frailers.net/articles/24/author ActionController::Routing::Routes.draw do |map| map.resources :articles do |article| article.resources :comments article.resource :author end end REST in Rails » Nested resources

More rails sugars Scaﬀolding script/generate scaffold article title:string body:text published:boolean Helpers link_to @article form_for @comment do |f| ... end redirect_to @article Authentication RESTful authentication plugin REST in Rails » Sugars

To sum up... Using REST in Rails is good lightweight controllers API given for free Rails is opinionated implementation of REST is not perfect REST in Rails » Conclusion

Best practices

Best practices Design methodology Real-life examples Best Practices

Disclaimer! Maybe “best” is an overstatement (is sounded great for the call for papers) ere are always diﬀerent solutions Best Practices » Disclaimer

Design methodology Knowing Rails’ resources API is great, but not suﬃcient e big question: what resources do I choose ? Best Practices » Design methodology

Classic beginner’s mistakes strictly mirroring your ActiveRecord data model to choose your resources thinking all 7 actions should be written for each and every resource and, of course, adding custom methods if the standard ones don’t ﬁt Best Practices » Design methodology

Resources are not models Well, to be fair, then can (and usually) represent models But also: Relations States Events (DHH told me so) Best Practices » Design methodology

Nouns are the new verbs Change your way of explaining a scenario, an action Use a noun to describe the action e noun given to your scenario is the resource you’re looking for A user subscribes to a group A subscription is created e project is validated by its owner A project validation is created e user deactivates his account A user account activation is deleted Best Practices » Design methodology

7 is not a strict target Resources can be read-only Sometimes, actions are meaningless: update an “account activation” ? really ? destroy a “page view” ? why ? Best Practices » Design methodology

Don’t be tempted! Rails allows extra, custom methods to be added to controllers, if you really need them But you’ll lose all what you were trying to do in the ﬁrst place (no uniform interface, etc.) I have never needed that (except, maybe...) If you do need that, it’s probable that you’d better rethink your architecture Best Practices » Design methodology

OK, you want real-life examples Adding/removing members from a group Dealing with object workﬂows Multi-step edition wizard Managing a shopping cart Manipulating several resource in one request Best Practices » Real-life examples

Adding / Removing members from a group Best Practices » Real-life examples

Dealing with object workﬂows Consider a CMS with all sorts of documents Each document has a status: draft, reviewed, published, ... Best Practices » Real-life examples

Dealing with object workﬂows Or another way : only “update” the document depending on the business logic, this can be considered overloading Best Practices » Real-life examples

Multi-step edition wizard A complex model needs to be edited in 3 steps, in a precise order Best Practices » Real-life examples

Multi-step edition wizard All these steps are diﬀerent, partial representations of the same resource Just GET the resource and put the step as a parameter Update the resource at each step... and redirect to the next step representation Best Practices » Real-life examples

Multi-step edition wizard Best Practices » Real-life examples

Managing a shopping cart We keep in the database the state of the shopping cart for each user: /users/21/shopping_cart_items Yes, but I don’t want the cart to be persistent Delete from the database when the user logs out Best Practices » Real-life examples

Manipulating two resources simultaneously You’re not manipulating two resources You’re manipulating a couple of things e resource is the couple Create guy, create girl => Create couple Best Practices » Real-life examples

Manipulating two resources simultaneously If you still need to do it in several steps... CREATE a Transaction resource PUT the ﬁrst part PUT the second part commit (PUT “committed”) or revert (DELETE) Best Practices » Real-life examples

ere are still some limitations... I want to choose items to delete from a list with checkboxes DELETE only works for a single resource at a time What you’re doing is updating the parent resource If there’s no parent resource, you’re screwed Best Practices » Real-life examples

ank you! It’s lunch time! Let’s eat! Let’s create some LunchEatings ! POST /lunch_eatings

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