class ActionDispatch::Cookies::CookieJar

def []=(key, options)

value, or a hash of options as documented above.
Sets the cookie named +name+. The second argument may be the very cookie 
def []=(key, options)
  if options.is_a?(Hash)
    options.symbolize_keys!
    value = options[:value]
  else
    value = options
    options = { :value => value }
  end
  value = super(key.to_s, value)
  handle_options(options)
  @set_cookies[key] = options
  @delete_cookies.delete(key)
  value
end