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webmachine for Ruby

Gem Version Build Status

webmachine-ruby is a port of Webmachine, which is written in Erlang. The goal of both projects is to expose interesting parts of the HTTP protocol to your application in a declarative way. This means that you are less concerned with the procedures involved in handling requests directly and more with describing facts about the resources that make up your application. Webmachine is not a web framework per se, but more of a toolkit for building HTTP-friendly applications. For example, it does not provide a templating engine or a persistence layer; those choices are up to you.


  • Handles the hard parts of content negotiation, conditional requests, and response codes for you.
  • Provides a base resource with points of extension to let you describe what is relevant about your particular resource.
  • Supports WEBrick and a Rack shim. Other host servers are being investigated.
  • Streaming/chunked response bodies are permitted as Enumerables, Procs, or Fibers!
  • Unlike the Erlang original, it does real Language negotiation.
  • Includes a visual debugger so you can look through the decision graph to determine how your resources are behaving.

Documentation & Finding Help

Getting Started

Below we go through some examples of how to do basic things with webmachine-ruby.

The first example defines a simple resource that doesn't demo the true power of Webmachine but perhaps gives a feel for how a Webmachine resource might look. is available to provide for quick prototyping and development. In a real application you will want to configure what path a resource is served from. See the Router section in the README for more details on how to do that.

There are many other HTTP features exposed to a resource through {Webmachine::Resource::Callbacks}. A callback can alter the outcome of the decision tree Webmachine implements, and the decision tree is what makes Webmachine unique and powerful.

A simple static HTML resource

require 'webmachine'

class MyResource < Webmachine::Resource
  def to_html
    "<html><body>Hello, world!</body></html>"

# Start a web server to serve requests via localhost

A simple dynamic JSON Resource

require 'webmachine'
require 'widget'

class MyResource < Webmachine::Resource

  # GET and HEAD are allowed by default, but are shown here for clarity.
  def allowed_methods

  def content_types_provided
    [['application/json', :to_json]]

  # Return a Truthy or Falsey value
  def resource_exists?

  def widget
    @widget ||= Widget.find(request.path_info[:id])

  def to_json


The router is used to map a resource to a given path. To map the class MyResource to the path /myresource you would write something along the lines of:

Webmachine.application.routes do
  add ['myresource'], MyResource

# Start a web server to serve requests via localhost

When the resource needs to be mapped with variables that will be passed into the resource, use symbols to identify which path components are variables.

Webmachine.application.routes do
  add ['myresource', :id], MyResource

To add more components to the URL mapping, simply add them to the array.

Webmachine.application.routes do
  add ['myparentresource', :parent_id, 'myresource', :id], MyResource

Read more about routing here.


There is a configurator that allows you to set what IP address and port a web server should bind to as well as what web server should serve a webmachine resource. Learn how to configure your application here.


Webmachine provides adapters for many popular webservers. Learn more here.

Visual debugger

It can be hard to understand all of the decisions that Webmachine makes when servicing a request to your resource, which is why we have the "visual debugger". Learn how to configure it here.

Related libraries


webmachine-ruby is licensed under the Apache v2.0 license. See LICENSE for details.