request_method_overer.rb

# This rack app overrides http method by __method=xxx query.
#
# Example
#
#   link_to 'Destroy', post_path(@post, :__method => :delete)
class RequestMethodOverrider
  HTTP_METHODS = %w(GET HEAD PUT POST DELETE OPTIONS)
  HTTP_METHOD_OVERRIDE_KEY = "__method".freeze

  def initialize(app)
    @app = app
  end

  def call(env)
    method = Rack::Utils.parse_query(env["QUERY_STRING"])[HTTP_METHOD_OVERRIDE_KEY].try(:upcase)
    env["REQUEST_METHOD"] = method if HTTP_METHODS.include?(method)
    @app.call(env)
  end
end