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lib | ||
test | ||
.gitignore | ||
.travis.yml | ||
CHANGELOG.md | ||
Gemfile | ||
MIT-LICENSE | ||
README.md | ||
Rakefile | ||
rabl-rails.gemspec |
README.md
RABL for Rails
RABL (Ruby API Builder Language) is a ruby templating system for rendering resources in different format (JSON, XML, BSON, ...). You can find documentation here.
rabl-rails is faster and uses less memory than the standard rabl gem while letting you access the same features. There are some slight changes to do on your templates to get this gem to work but it should't take you more than 5 minutes.
rabl-rails only targets Rails 3+ application and is compatible with mri 1.9.3, jRuby and rubinius.
Installation
Install as a gem :
gem install rabl-rails
or add directly to your Gemfile
gem 'rabl-rails'
And that's it !
Overview
Once you have installed rabl-rails, you can directly used RABL-rails templates to render your resources without changing anything to you controller. As example,
assuming you have a Post
model filled with blog posts, and a PostController
that look like this :
class PostController < ApplicationController
respond_to :html, :json, :xml
def index
@posts = Post.order('created_at DESC')
respond_with(@posts)
end
end
You can create the following RABL-rails template to express the API output of @posts
# app/views/post/index.rabl
collection :@posts
attributes :id, :title, :subject
child(:user) { attributes :full_name }
node(:read) { |post| post.read_by?(@user) }
This would output the following JSON when visiting http://localhost:3000/posts.json
[{
"id" : 5, title: "...", subject: "...",
"user" : { full_name : "..." },
"read" : true
}]
That's a basic overview but there is a lot more to see such as partials, inheritance or fragment caching.
How it works
As opposed to standard RABL gem, this gem separate compiling (a.k.a transforming a RABL-rails template into a Ruby hash) and the actual rendering of the object or collection. This allow to only compile the template once and only Ruby hashes.
The fact of compiling the template outside of any rendering context prevent us to use any instances variables (with the exception of node) in the template because they are rendering objects. So instead, you'll have to use symbols of these variables.For example, to render the collection @posts
inside your PostController
, you need to use :@posts
inside of the template.
The only places where you can actually used instance variables are into Proc (or lambda) or into custom node (because they are treated as Proc).
# We reference the @posts varibles that will be used at rendering time
collection :@posts
# Here you can use directly the instance variable because it
# will be evaluated when rendering the object
node(:read) { |post| post.read_by?(@user) }
The same rule applies for view helpers such as current_user
After the template is compiled into a hash, Rabl-rails will use a renderer to do the actual output. Actually, only JSON and XML formats are supported.
Configuration
RablRails works out of the box, with default options and fastest engine available (oj, libxml). But depending on your needs, you might want to change that or how your output looks like. You can set global configuration in your application:
# config/initializers/rabl_rails.rb
RablRails.configure do |config|
# These are the default
# config.cache_templates = true
# config.include_json_root = true
# config.json_engine = :oj
# config.xml_engine = 'LibXML'
# config.use_custom_responder = false
# config.default_responder_template = 'show'
end
Usage
Data declaration
To declare data to use in the template, you can use either object
or collection
with the symbol name or your data.
# app/views/users/show.json.rabl
object :@user
# app/views/users/index.json.rabl
collection :@users
You can specify root label for the collection using hash or :root
option
collection :@posts, root: :articles
#is equivalent to
collection :@posts => :articles
# => { "articles" : [{...}, {...}] }
There are rares cases when the template doesn't map directly to any object. In these cases, you can set data to false or skip data declaration altogether.
object false
node(:some_count) { |_| @user.posts.count }
child(:@user) { attribute :name }
If you use gem like decent_exposure or focused_controller, you can use your variable directly without the leading @
object :object_exposed
You can even skip data declaration at all. If you used respond_with
, rabl-rails will render the data you passed to it.
As there is no name, you can set a root via the root
macro. This allow you to use your template without caring about variables passed to it.
# in controller
respond_with(@post)
# in rabl-rails template
root :article
attribute :title
Attributes / Methods
Basic usage is to declared attributes to include in the response. These can be database attributes or any instance method.
attributes :id, :title, :to_s
You can aliases these attributes in your response
attributes title: :foo, to_s: :bar
# => { "foo" : <title value>, "bar" : <to_s value> }
Child nodes
You can include nested information from data associated with the parent model. You can also alias these associations.
For example if you have a Post
model that belongs to a User
object :@post
child(user: :author) do
attributes :name
end
# => { "post" : { "author" : { "name" : "John D." } } }
You can also use arbitrary data source with child nodes
child(:@users) do
attributes :id, :name
end
Custom nodes
You can create custom node in your response, based on the result of the given block
object :@user
node(:full_name) { |u| u.first_name + " " + u.last_name }
# => { "user" : { "full_name" : "John Doe" } }
You can add the node only if a condition is true
node(:email, if: -> { |u| u.valid_email? }) do |u|
u.email
end
Nodes are evaluated at the rendering time, so you can use any instance variables or view helpers inside them
node(:url) { |post| post_url(post) }
Custom nodes are really usefull to create flexible representations of your resources.
Extends & Partials
Often objects have a basic representation that is shared accross different views and enriched according to it. To avoid code redundancy you can extend your template from any other RABL template.
# app/views/users/base.json.rabl
attributes :id, :name
# app/views/users/private.json.rabl
extends 'users/base'
attributes :super_secret_attribute
You can also extends template in child nodes using partial
option (this is the same as using extends
in the child block)
collection @posts
attribute :title
child(:user, partial: 'users/base')
Partials can also be used inside custom nodes. When using partial this way, you MUST declare the object associated to the partial
node(:location) do |user|
{ city: user.city, address: partial('users/address', object: m.address) }
end
Nesting
Rabl allow you to define easily your templates, even with hierarchy of 2 or 3 levels. Let's suppose your have a thread
model that has many posts
and that each post has many comments
. We can display a full thread in a few lines
object :@thread
attribute :caption
child :posts do
attribute :title
child :comments do
extends 'comments/base'
end
end
Render object directly
There are cases when you want to render object outside Rails view context. For instance to render objects in the console or to create message queue payloads. For these situations, you can use RablRails.render
as show below:
Rabl.render(object, template, :view_path => 'app/views', :format => :json) #=> "{...}"
You can find more informations about how to use this method in the wiki
Other features
You can find more informations about other features (caching, custom_responder, ...) in the WIKI
Performance
Benchmarks have been made using this application, with rabl 0.7.6 and rabl-rails 0.3.0
Overall, Rabl-rails is 20% faster and use 10% less memory, even twice faster when using extends.
You can see full tests on test application repository.
Authors and contributors
- Christopher Cocchi-Perrier - Creator of the project
Want to add another format to Rabl-rails ? Checkout JSON renderer for reference Want to make another change ? Just fork and contribute, any help is very much appreciated. If you found a bug, you can report it via the Github issues.
Original idea
- RABL Standart RABL gem. I used it a lot but I needed to improve my API response time, and since most of the time was spent in view rendering, I decided to implement a faster rabl gem.
Copyright
Copyright © 2011-2012 Christopher Cocchi-Perrier. See MIT-LICENSE for details.