Let’s see what happens with the POST request without specifying the response.
Rails happily returns with 204: No content response in this case.
This means users get the feel that nothing happened in the browser. Because Rails
returned with no content and browser happily accepted it.
But in reality, the user record was created in the database.
what happens with the GET request
in Rails 5.
Instead of 204: No Content, we get ActionController::UnknownFormat exception.
Rails is being extra smart here and hinting that we are probably missing
corresponding template for this controller action. It is smart enough to show us
this message as we requested this page via browser via a GET request.
But if the same request is made
via Ajax or through an API call or a POST request, Rails will return 204: No Content response as seen before.
In general, this change can trip us in the development phase, as we are used
to incremental steps like adding a route, then the controller action and then
the template or response. Getting 204 response can give a feel of nothing happening
where things have actually happened in the background. So don’t forget to respond properly
from your controller actions.