Represents an HTTP response generated by a controller action. Use it to retrieve the current state of the response, or customize the response. It can either represent a real HTTP response (i.e. one that is meant to be sent back to the web browser) or a TestResponse (i.e. one that is generated from integration tests).
Response is mostly a Ruby on Rails framework implementation detail, and should never be used directly in controllers. Controllers should use the methods defined in ActionController::Base instead. For example, if you want to set the HTTP response's content MIME type, then use ActionControllerBase#headers instead of Response#headers.
Nevertheless, integration tests may want to inspect controller responses in more detail, and that's when Response can be useful for application developers. Integration test methods such as ActionDispatch::Integration::RequestHelpers#get and ActionDispatch::Integration::RequestHelpers#post return objects of type TestResponse (which are of course also of type Response).
For example, the following demo integration test prints the body of the controller response to the console:
class DemoControllerTest < ActionDispatch::IntegrationTest
def test_print_root_path_to_console
get('/')
puts response.body
end
end