Listing controller filters in Rails 4
While trying to debug some filter/callback weirdness in a Rails 4 app, I tried to work out how to list all the callbacks for an action. I spent a while digging through the code until I found out that you could get the callbacks from the
_process_action_callbacks method. So, popping something like this in your index action will write all the callbacks to the page. Magic.
def index render text: self._process_action_callbacks end
 There’s every chance that this same method works in earlier versions of Rails but I haven’t tried it.