First thing's first, you're probably asking yourself - "Why the ridiculous name?". It's simple, really - RocketPants is memorable, and sounds completely bad ass. - everything a library needs.
At its core, RocketPants is a set of tools (built around existing toolsets such as ActionPack) to make it easier to build well-designed APIs in Ruby and more importantly, along side Rails. You can think of it like Grape, a fantastic library which RocketPants was originally inspired by but with deeper Rails and ActionPack integration.
Why use RocketPants over alternatives like Grape or normal Rails? The reasons we built it come down to a couple of simple things:
- It's opinionated (like Grape) - In this case, we dictate a certain JSON structure we've found nice to work with (after having worked with and investigated a large number of other apis), it makes it simple to add metadata along side requests and the like.
- Simple and Often Automatic Response Metadata - RocketPants automatically takes care of sending metadata about paginated responses and arrays where possible. This means as a user, you only need to worry about writing
expose object_or_presenter
in your controller and RocketPants will do it's best to send as much information back to the user. - Extended Error Support - RocketPants has a built in framework to manage errors it knows how to handle (in the forms of mapping exceptions to a well defined JSON structure) as well as tools to make it simple to hook up to Airbrake and do things such as including an error identifier in the response.
- It's built on ActionPack - One of the key differentiators to Grape is that RocketPants embraces ActionPack and uses the modular components included from Rails 3.0 onwards to provide things you're familiar with already such as filters.
- Semi-efficient Caching Support - Thanks to a combination of Rails middleware and collection vs. resource distinctions, RocketPants makes it relatively easy to implement "Efficient Validation" (See here). As a developer, this means you get even more benefits of http caching where possible, without the need to generate full requests when etags are present.
- Simple tools to consume RocketPants apis - RocketPants includes the
RocketPants::Client
class which builds upon APISmith to make it easier to build clients e.g. automatically converting paginated responses back.
Learn better by reading code? There is also have an example app mixing models and api clients over at Sutto/transperth-api that is built using RocketPants.
Say, for example, you have a basic Food model:
class Food < ActiveRecord::Base
include RocketPants::Cacheable
end
class FoodsController < RocketPants::Base
version 1
# The list of foods is paginated for 5 minutes, the food itself is cached
# until it's modified (using Efficient Validation)
caches :index, :show, :caches_for => 5.minutes
def index
expose Food.paginate(:page => params[:page])
end
def show
expose Food.find(params[:id])
end
end
And in the router we'd just use the normal REST-like routes in Rails:
api :version => 1 do
resources :foods, :only => [:index, :show]
end
And then, using this example, hitting GET http://localhost:3000/1/foods
would result in:
{
"response": [{
"id": 1,
"name": "Delicious Food"
}, {
"id": 2,
"name": "More Delicious Food"
}],
"count": 2,
"pagination": {
"previous": nil,
"next": nil,
"current": 1,
"per_page": 10,
"count": 2,
"pages": 1
}
}
with the Cache-Control
header set whilst hitting GET http://localhost:3000/1/foods/1
would return:
{
"response": {
"id": 1,
"name": "Delicious Food"
}
}
with the Etag
header set.
Using the example above, we could then use the following to write a client:
class FoodsClient < RocketPants::Client
version 1
base_uri 'http://localhost:3000'
class Food < APISmith::Smash
property :id
property :name
end
def foods
get 'foods', :transformer => Food
end
def food(id)
get "foods/#{id}", :transformer => Food
end
end
RocketPants builds upon the mixin-based approach to ActionController-based rails applications that Rails 3 made possible. Instead of including everything like Rails does in ActionController::Base
, RocketPants only includes the bare minimum to make apis. In the near future, it may be modified to work with ActionController::Base
for the purposes of better compatibility with other gems.
Out of the box, we use the following ActionController components:
ActionController::HideActions
- Lets you hide methods from actions.ActionController::UrlFor
-url_for
helpers / tweaks by Rails to make integration with routes work better.ActionController::Redirecting
- Allows you to useredirect_to
.ActionController::ConditionalGet
- Adds support for Rails caching controls, e.g.fresh_when
andexpires_in
.ActionController::RackDelegation
- Lets you reset the session and set the response body.ActionController::RecordIdentifier
- Givesdom_class
anddom_id
methods, used for polymorphic routing.ActionController::HttpAuthentication
Mixins - Gives Token, Digest and Basic authentication.AbstractController::Callbacks
- Adds support for callbacks / filters.ActionController::Rescue
- Lets you userescue_from
.
And added our own:
RocketPants::UrlFor
- Automatically includes the current version when generating URLs from the controller.RocketPants::Respondable
- The core of RocketPants, the code that handles converting objects to the different container types.RocketPants::Versioning
- Allows versioning requirements on the controller to ensure it is only callable with a specific api version.RocketPants::Instrumentation
- Adds Instrumentation notifications making it easy to use and hook into with Rails.RocketPants::Caching
- Implements time-based caching for index actions and etag-based efficient validation for singular resources.RocketPants::ErrorHandling
- Short hand to create errors as well as simplifications to catch and render a standardised error representation.RocketPants::Rescuable
- Allows you to hook in to rescuing exceptions and to make it easy to post notifications to tools such as AirBrake.
To use RocketPants, instead of inheriting from ActionController::Base
, just inherit from RocketPants::Base
.
Likewise, in Rails applications RocketPants also adds RocketPants::CacheMiddleware
before the controller endpoints to implement "Efficient Validation".
Installing RocketPants is a simple matter of adding:
gem 'rocket_pants', '~> 1.0'
To your Gemfile
and running bundle install
. Next, instead of inherited from ActionController::Base
, simply inherit from RocketPants::Base
instead. If you're working with an API-only application, I typically change this in ApplicationController
and inherit from ApplicationController
as usual. Otherwise, I generate a new ApiController
base controller along side ApplicationController
which instead inherits from RocketPants::Base
and place all my logic there.
Setting up RocketPants in your rails application is pretty simple and requires a minimal amount of effort. Inside your environment configuration, RocketPants offers the following options to control how it's configured (and their expanded alternatives):
config.rocket_pants.use_caching
- Defaulting to true for production environments and false elsewhere, defines whether RocketPants caching setup as described below is used.config.rocket_pants.cache
- AMoneta::Store
instance used as the RocketPants cache, defaulting to a moneta memory instance. Change for proper caching. (See here for more information on Moneta.)
The current preferred way of dealing with version APIs in RocketPants is to do it using routes in the form of /:version/:endpoint
- e.g. GET /1/users/324
. RocketPants has support in the router and controller level for enforcing and controlling this. In the controller, it's a matter of specifying the required API versions:
class UsersController < RocketPants::Base
version 1 # A single version
# or...
version 2..3 # 2-3 support this controller
end
And in the case of multiple versions, I strongly encourage namespaces the controllers inside modules. If the version param (as specified) by the URL does not match, then the specified controller will return an :invalid_version
error as shown below.
Next, in your config/routes.rb
file, you can also declare versions using the following syntax and it will automatically set up the routes for you:
api :version => 1 do
get 'x', :to => 'test#item'
end
Which will route GET /1/x
to TestController#item
.
Likewise, you can specify a route for multiple versions by:
api :versions => 1..3 do
get 'x', :to => 'test#item'
end
When using RocketPants, you write your controllers the same as how you would with normal ActionController, the only thing that changes is how you handle data. head
and redirect_to
still work exactly the same as in Rails, but instead of using respond_with
and render
you instead use RocketPant's exposes
methods (and it's kind). Namely:
expose
/exposes
- The core of all type conversion, will check the type of data and automatically convert it to the correct time (for either a singular, collection or paginated resource).paginated
- Render an object as a paginated collection of data.collection
- Renders a collection of objects - e.g. an array of users.resource
- Renders a single object.
Along side the above that wrap data, it also provides:
responds
- Renders JSON, normalizing the object first (unwrapped).render_json
- Renders an object as JSON.
Singular resources will be converted to JSON via serializable_hash
, passing through any objects
and then wrapped in an object as the response
key:
{
"response": {
"your": "serialized-object"
}
}
Similar to singular resources, but also include extra data about the count of items.
{
"response": [{
"name": "object-one"
}, {
"name": "object-two"
}],
"count": 2
}
The final type, similar to collection objects but it includes details about the paginated data:
{
"response": [
{"name": "object-one"},
{"name": "object-two"},
{"name": "object-three"},
{"name": "object-four"},
{"name": "object-five"}
],
"count": 5,
"pagination": {
"previous": 1,
"next": 3,
"current": 2,
"per_page": 5,
"count": 23,
"pages": 5
}
}
One of the built in features of RocketPants is the ability to handle rescuing / controlling exceptions and more importantly to handle mapping exceptions to names, messages and error codes.
This comes in useful when you wish to automatically convert exceptions such as ActiveRecord::RecordNotFound
to a structured bit of data in the response. Namely, it makes it trivial to generate objects that follow the JSON structure of:
{
"error": "standard_error_name",
"error_description": "A translated error message describing what happened."
}
It also adds a facilities to make it easy to add extra information to the response.
RocketPants will also attempt to convert all errors in the controller, defaulting to the "system"
exception name and message as the error description. We also provide a registry to allow throwing exception from their symbolic name like so:
error! :not_found
In the controller.
Out of the box, the following exceptions come pre-registered and setup:
:throttled
- The user has hit an api throttled error.:unauthenticated
- The user doesn't have valid authentication details.:invalid_version
- An invalid API version was specified.:not_implemented
- The specified endpoint is not yet implemented.:not_found
- The given resource could not be found.
One of the core design principles built into RocketPants is simple support for "Efficient Validation" as described in the Rack::Cache FAQ - Namely, it adds simple support for object-level caching using etags with fast verification thanks to the RocketPants::CacheMiddleware
cache middleware.
To do this, it uses RocketPants.cache
, by default any Moneta-based store, to keep a mapping of object -> current cache key. RocketPants will then generate the etag when caching is enabled in the controller for singular-responses, generating an etag that can be quickly validated.
For example, you'd add the following to your model:
class User < ActiveRecord::Base
include RocketPants::Cacheable
end
And then in your controller, you'd have something like:
class UsersController < RocketPants::Base
version 1
# Time based, e.g. collections, will be cached for 5 minutes - whilst singular
# items e.g. show will use etag-based caching:
caches :show, :index, :caches_for => 5.minutes
def index
expose User.all
end
def show
expose User.find(params[:id])
end
end
When the user hits the index endpoint, it will generate an expiry-based caching header that caches the result for up to 5 minutes. When the user instead hits the show endpoint, it will generate a special etag that contains and object identifier portion and an object cache key. Inside RocketPants.cache
, we store the mapping and then inside RocketPants::CacheMiddleware
, we simply check if the given cache key matches the specified object identifier. If it does, we return a not modified response otherwise we pass it through to controller - giving the advantage of efficient caching without having to hit the full database on every request.
When testing controllers written using RocketPants, your normal rails approach should work.
The only difference one needs to take into the account is the need to specify the :version
parameter on any http requests, e.g:
get :index, :version => 1
Otherwise it will raise an exception.
RocketPants includes a set of helpers to make testing controllers built on RocketPants::Base
simpler.
be_singular_resource
- Checks the response is a single resource - e.g.response.should be_siingular_resource
.be_collection_resource
- Checks the response is collection of resources - e.g.response.should be_collection_resource
.be_paginated_response
- Checks the response is paginated - e.g.response.should be_paginated_response
.be_api_error(type = any)
- Checks it returned an error for the specified exception (or check the response is an error without any argument) - e.g.response.should be_api_error RocketPants::NotFound
.have_exposed(data, options = {})
- Given an object and conversion options, lets you check the output exposed the same object. e.g:response.should have_exposed user
Likewise, it adds the following helper methods:
parsed_body
- A parsed-JSON representation of the response.decoded_body
- AHashie::Mash
of the response body.
To set up the integration, in your spec/spec_helper.rb
add:
config.include RocketPants::TestHelper, :type => :controller
config.include RocketPants::RSpecMatchers, :type => :controller
Inside the RSpec.configure do |config|
block.
- Darcy Laycock - Main developer, current maintainer.
- Steve Webb - Helped with original work at The Frontier Group, inc. original design.
- Fred Wu - README fixes.
- Levi Buzolic - README fixes.
We encourage all community contributions. Keeping this in mind, please follow these general guidelines when contributing:
- Fork the project
- Create a topic branch for what you’re working on (git checkout -b awesome_feature)
- Commit away, push that up (git push your_remote awesome_feature)
- Create a new GitHub Issue with the commit, asking for review. Alternatively, send a pull request with details of what you added.
- Once it’s accepted, if you want access to the core repository feel free to ask! Otherwise, you can continue to hack away in your own fork.
Other than that, our guidelines very closely match the GemCutter guidelines here.
(Thanks to GemCutter for the contribution guide)
RocketPants is released under the MIT License (see the license file) and is copyright Filter Squad, 2012.