I have the following controller code:
def create
@admin = Admin.new(params[:admin])
respond_to do |format|
if @admin.save
redirect_to
I started having this issue after a deploy in production, even tough everything was working fine in development.
After some 15 minutes of wasted time, I finally found out that I had forgotten to commit some of the view files (like index.html.erb).
Using tail -f log/production.log on the server revealed: FATAL -- : ActionController::UnknownFormat (SomeController#index is missing a template for this request format and variant.
In development the error didn't happen because, obviously, the view file was present.