Wrest 1.4.3

© Copyright 2009-2011 Sidu Ponnappa. All Rights Reserved.

Wrest is a ruby REST/HTTP client library which

  • Allows you to use Net::HTTP or libCurl

  • Allows you to pick your Ruby: use 1.8.7, 1.9.2, JRuby and Rubinius (Continuous Integration server)

  • Supports RFC 2616 based caching

  • Alpha

    Allows you to go async: use Threads or EventMachine

  • Allows you to quickly build object oriented wrappers around any web service

  • Is designed to be used as a library, not just a command line REST client (fewer class/static methods, more object oriented)

  • Is spec driven, strongly favours immutable objects and avoids class methods and setters making it better suited for use as a library, especially in multi-threaded environments

  • Provides convenient HTTP wrappers, redirect handling, serialisation, deserialisation and xpath based lookup

To receive notifications whenever new features are added to Wrest, please subscribe to my twitter feed.


For Facebook, Twitter, Delicious, GitHub and other API examples, see github.com/kaiwren/wrest/tree/master/examples

Basic Http Calls


  • Basic API calls

    'http://twitter.com/statuses/public_timeline.json'.to_uri.get.deserialise  # works with json and xml out of the box
    'http://twitter.com/statuses/public_timeline.xml'.to_uri.get.deserialise   # see lib/wrest/components/translators to add other formats
  • Timeout support

    'http://twitter.com/statuses/public_timeline.json'.to_uri.get(:timeout => 5).body
  • Redirect support

    'http://google.com'.to_uri(:follow_redirects => false).get
    'http://google.com'.to_uri(:follow_redirects_limit => 1).get

    :follow_redirects_limit defaults to 5 if not specified.

  • Deserialise with XPath filtering

    ActiveSupport::XmlMini.backend = 'REXML'
                                                  :xpath => '//user/name/text()'
  • More complex request with parameters and a custom deserialiser

                  :appid  => 'YahooDemo', 
                  :output => 'xml',
                  :query  => 'India',
                  :results=> '3',
                  :start  => '1'
  • Basic HTTP auth and URI extensions using Wrest::Uri#[]

    base_uri = 'https://api.del.icio.us/v1'.to_uri(:username => 'kaiwren', :password => 'fupupp1es')
    bookmarks = base_uri['/posts/get'].get.deserialise


  • Regular, vanilla Post with a body and headers

    'http://my.api.com'.to_uri.post('YAML encoded body', 'Content-Type' => 'text/x-yaml')
  • Form encoded post

             :username => 'kaiwren', :password => 'fupupp1es'
             :url => 'http://blog.sidu.in/search/label/ruby',
             :description => 'The Ruby related posts on my blog!',
             :extended => "All posts tagged with 'ruby'",
             :tags => 'ruby hacking'
  • Multipart posts

      :image => UploadIO.new(File.open(file_path), "image/png", file_path), 
      :key => imgur_key


To delete a resource:

                                             :username => 'kaiwren',
                                             :password => 'fupupp1es'
                                             :url => 'http://c2.com'


Wrest supports caching with pluggable back-ends.

Wrest::Caching.default_to_hash!     # Hash should NEVER be used in a production environment. It is unbounded and will keep increasing in size.
c42 = "http://c42.in".to_uri.get

A Memcached based caching back-end is available in Wrest. You can get instructions on how to install Memcached on your system here. The Dalli gem is used by Wrest to interface with Memcached. Install dalli using 'gem install dalli'.

Use the following method to enable caching for all requests, and set Memcached as the default back-end.


For fine-grained control over the cache store (or to use multiple cache stores in the same codebase), you can use this API:

r1 = "http://c42.in".to_uri.using_memcached.get
r2 = "http://c42.in".to_uri.using_hash.get

A detailed writeup regarding caching as defined by RFC 2616, and how Wrest implements caching is at Wrest Caching Doc

You can create your own back-ends for Wrest caching by implementing the interface implemented in github.com/kaiwren/wrest/blob/master/lib/wrest/components/cache_store/memcached.rb

To explicitly disable caching for specific requests:



Uri level callbacks

You can define a set of callbacks that are invoked based on the http codes of the responses to any requests on a given uri.

"http://google.com".to_uri(:callback => {
            200      => lambda {|response| Wrest.logger.info "Ok." },
            400..499 => lambda {|response| Wrest.logger.error "Invalid. #{response.body}"},
            300..302 => lambda {|response| Wrest.logger.debug "Redirected. #{response.message}" }

Per request callbacks

You can also define callbacks that are invoked based on the http code of the response to a particular request.

"http://google.com".to_uri.get do |callback|
  callback.on_ok do |response|
    Wrest.logger.info "Ok."

  callback.on(202) do |response|
    Wrest.logger.info "Accepted."

  callback.on(200..206) do |response|
    Wrest.logger.info "Successful."

Please note that Wrest is a synchronous library. All requests are blocking, and will not return till the request is completed and appropriate callbacks executed.

Asynchronous requests

Asynchronous requests are non-blocking. They do not return a response and the request is executed on a separate thread. The only way to access the response while using asynchronous request is through callbacks.

Asynchronous requests support pluggable backends. The default backend used for asynchronous requests is ruby threads.

"http://c42.in".to_uri.get_async do |callback|
  callback.on_ok do |response|
    Wrest.logger.info "Ok."

sleep 1 # Causes thread created by get_async to execute

You can change the default to eventmachine.


You can also override the default on Uri objects.

"http://c42.in".to_uri.using_em.get_async do |callback|
  callback.on_ok do |response|
    Wrest.logger.info "Ok."

Note: The current implementation of asynchronous requests is currently in alpha and should not be used in production.

Other useful stuff

Allows any class to hold an attributes hash, somewhat like ActiveResource. It also supports several extensions to this base fuctionality such as support for typecasting attribute values. See examples/twitter.rb and examples/wow_realm_status.rb for more samples.


class Demon
  include Wrest::Components::Container

  always_has       :id
  typecast         :age          =>  as_integer,
                   :chi          =>  lambda{|chi| Chi.new(chi)}

  alias_accessors  :chi => :energy                  

kai_wren = Demon.new('id' => '1', 'age' => '1500', 'chi' => '1024', 'teacher' => 'Viss')
kai_wren.id       # => '1'
kai_wren.age      # => 1500
kai_wren.chi      # => #<Chi:0x113af8c @count="1024">
kai_wren.energy   # => #<Chi:0x113af8c @count="1024">
kai_wren.teacher  # => 'Viss'


The Wrest logger can be set and accessed through Wrest.logger and is configured by default to log to STDOUT. If you're using Wrest in a Rails application, you can configure logging by adding a config/initializers/wrest.rb file with the following contents :

Wrest.logger = Rails.logger


Standard options are available and can be listed using rake -T. Use rake:rcov for coverage and rake:rdoc to generate documentation. The link to the continuous integration build is over at the C42 Engineering open source page.


Wrest RDocs can be found at wrest.rubyforge.org


Features that are planned, in progress or already implemented are documented in the CHANGELOG starting from version 0.0.8.


The source is available at git://github.com/kaiwren/wrest.git

To install the Wrest gem, do (sudo) gem install wrest.

Wrest is currently available as a gem for for Ruby and JRuby.


You can launch the interactive Wrest shell by running bin/wrest if you have the source or invoking wrest from your prompt if you've installed the gem.

$ wrest
>> y 'http://twitter.com/statuses/public_timeline.json'.to_uri(:timeout => 5).get.deserialise


Start the Sinatra test server for functional test.

rake -f spec/sample_app/Rakefile  # runs on port 3000

Start a memcached daemon/process on port 11211


Run the tests in a different terminal:

# Run the normal test suite.

# Runs the functional test suite.
rake rspec:functional