Add support for the HTTP OPTIONS method to a Sinatra application.

add_support_for_HTTP_OPTIONS.rb

# The HTTP OPTIONS method allows for cross-site HTTP requests.
# For more information see https://developer.mozilla.org/en/HTTP_access_control
# and, of course, the HTTP spec (section 9.2) at http://www.w3.org/Protocols/rfc2616/rfc2616-sec9.html

# In this example, we plan to use it in development mode only
configure :development do
  # Open the Sinatra::Base class and add the method. We can't
  # use 'options' as the method name because there is already
  # an options method on the class.
  class << Sinatra::Base
    def http_options path, opts={}, &block
      route 'OPTIONS', path, opts, &block
    end
  end

  # This line is necessary if you are using Sinatra in the
  # classic (DSL) mode.
  Sinatra::Delegator.delegate :http_options

  # Finally, set up a route that matches any path and answer
  # back that we will allow cross-site requests from any host.
  # You obviously wouldn't do this in a production application,
  # that would be a huge security risk.
  http_options /.+/ do
    content_type = 'text/plain'
    response['Access-Control-Allow-Origin'] = '*'
    response['Access-Control-Allow-Credentials'] = 'true'
    response['Access-Control-Max-Age'] = (60 * 60 * 24 * 20).to_s # 20 days, in seconds
    ''
  end
end