weary

A framework and DSL for building RESTful web service clients

477

Ruby

Weary

Weary is a framework and DSL for building clients for (preferably RESTful) web service APIs.

At its most minimal, Weary is simply some nice syntactic sugar around Net/HTTP.

If you dig a bit deeper, it’s a suite of tools built around the Rack ecosystem. As you build a client, remember that just about every class in Weary is a piece of Rack middleware or a Rack application underneath the covers.

It features:

Full Rack integration:

There are points in the stack to hook in Rack middleware and just about every class in Weary is a Rack application in its own right.
Asynchronous:

Weary::Request#perform, the thing that performs the request, returns a future and only blocks when accessed.

It takes its inspiration from HTTParty and Faraday.

Quick Start

# http://developer.github.com/v3/repos/
class GithubRepo < Weary::Client
  domain "https://api.github.com"

  use Rack::Lint

  get :list_user_repos, "/users/{user}/repos" do |resource|
    resource.optional :type
  end

  get :get, "/repos/{user}/{repo}"
end

client = GithubRepo.new
client.list_user_repos(:user => "mwunsch").perform do |response|
  puts response.body if response.success?
end

This is a basic example of a client you will build using the Weary framework. If you’re coming from a previous version of Weary, you would have created a subclass of Weary::Base. That’s one of the many changes in the big rewrite.

Weary::Client

Inherit from Weary::Client for a set of class methods that craft “Resources” (more on that later).

class MyClass < Weary::Client
  get :resource, "http://host.com/path/to/resource" do |resource|
    resource.optional :optional_parameter
  end
end

The DSL provides methods for all of the HTTP verbs (See Weary::Client::REQUEST_METHODS). When you instantiate this class, the object will have an instance method named “resource” that will return a Weary::Request object set up to perform a “GET” request on “http://host.com/path/to/resource”.

You can pass a block to these methods for access to the Weary::Resource.

Further methods in the DSL include:

domain   - This will be prepended to every path when resources are defined
             (Particularly useful when using Client's Rack integration, discussed below).
optional - See Resource section below.
required - See Resource section below.
defaults - See Resource section below.
headers  - See Resource section below.
use      - A Rack::Middleware to place in the Request stack.
             (See Rack integration further down)

Weary::Resource

The resource is a building block used in Client to describe the requirements of a request.

optional    - A group of keys for parameters that the request expects.
required    - Keys that the request needs in order to be performed.
defaults    - Default parameters to be sent in every request.
headers     - Headers to send in the request.
user_agent  - A convenience method to set the User Agent header.
basic_auth! - Prepare the request to accept a username and password for basic authentication.
oauth!      - Prepare the request to accept the consumer key and access token in the request.

Finally, the request method of the Resource takes a set of parameters to verify that requirements are met and returns a Weary::Request object. It should all look something like this once all is said and done.

# https://dev.twitter.com/docs/api/1/post/statuses/update
post :update, "http://api.twitter.com/1/statuses/update.json" do |resource|
  resource.required :status
  resource.optional :in_reply_to_status_id, :lat, :long, :place_id,
                    :display_coordinates, :trim_user, :include_entities
  resource.oauth!
end

# After instantiating the client:
# (This calls the "update" resource's `request` method)
client.update :status       => "I'm tweeting from Weary",
              :consumer_key => "an_oauth_consumer_key",
              :token        => "my_oauth_access_token"

If a required parameter is missing, a Weary::Resource::UnmetRequirementsError exception is raised.

URL’s for these methods can also be dynamic. If we alter the above example:

post :update, "http://api.twitter.com/1/statuses/update.{format}" do |resource|

Then a key :format will be expected to be passed with the other parameters.

The method that the Client defines (in the above example, the client.update method), can take an optional block that allows you to manipulate the underlying Weary::Request object.

Weary::Request

No matter how you get there, you’ll end up with a Weary::Request object. Call the perform method to actually make the request and get back a Weary::Response. That’s not entirely true… Weary::Request#perform is asynchronous and non-blocking. It returns a future and will only block once you call a method on the response. You can optionally pass a block that’s executed once the response has returned.

By default, the request is performed through Net::HTTP. This is done through Weary::Adapter::NetHttp. A Weary::Adapter is just a special kind of Rack application. Request#adapter allows you to hook up your own. Weary also includes adapters for Typhoeus and Excon.

Requestable

Client, Resource, and Request include a Module named Requestable. Using this module, it’s easy to cascade certain pieces of configuration down from the stack.

For example, you can call Client#adapter to change the adapter for all of the resources of that client. Or you can call Resource#adapter to change the adapter for requests built for that resource. OR you can call Request#adapter to change the adapter for just that request.

Rack

To maximize the utility of Weary, it’s important to remember that driving everything is Rack. Almost every class is built to provide a Rack interface.

Every class that inherits from Weary::Client is a Rack application.

A Weary::Request is a Rack application. When you call Request#call it creates its own special Rack environment. In order to preserve your Rack middleware, you can add your middleware to the stack using Request#use.

When using Weary::Client the use method will add the passed middleware to every Request stack.

Authentication, by default is done by either Weary::Middleware::BasicAuth or Weary::Middleware::OAuth. Both are just Rack middleware, and can be used in any Rack stack.

The point is, it’s just Rack.

Weary needs your help.

At this point, I need your help to further Weary along. I’d love to see more examples that utilize the Rackness of Weary: using Devise, Warden, or mounted in a Rails application.

Examples

Gilt is a Ruby client to the Gilt public API. Notice how much of the code is dedicated to the Gilt domain model, and very little to actually interacting with the web service. That’s the idea.