Sets the format by string extension, which can be used to force custom formats that are not controlled by the extension. Example:

class ApplicationController < ActionController::Base
  before_filter :adjust_format_for_iphone

  private
    def adjust_format_for_iphone
      request.format = :iphone if request.env["HTTP_USER_AGENT"][/iPhone/]
    end
end

Source Code

# File action_controller/request.rb, line 114
def format=(extension)
  parameters[:format] = extension.to_s
  @format = Mime::Type.lookup_by_extension(parameters[:format])
end