Response.notModified({Map<String, String> headers, Map<String, Object> context})

Constructs a 304 Not Modified response.

This is used to respond to a conditional GET request that provided information used to determine whether the requested resource has changed since the last request. It indicates that the resource has not changed and the old value should be used.

Source 

Response.notModified({Map<String, String> headers,
  Map<String, Object> context})
    : this(304, headers: addHeader(
          headers, 'date', formatHttpDate(new DateTime.now())),
          context: context);