When using Rails 4, I had this strange error in
ActionMailer where the parameters being passed to one of the mailer methods became a string called
_process_action_callbacks. There was zero Google result, and it took me a while to figure this out.
It turns out that I was naming one of the ActionMailer methods as
send is a special method in Ruby, and I was overwriting it. But I didn’t see this immediately because the error string
_process_action_callbacks was being generated somewhere from
AbstractController. I also compmletely forgot that mailer methods should be nouns and not verbs.
Side Note on Sidekiq
I also got stuck because I was passing symbols to a Sidekiq worker. Sidekiq converts symbols into strings:
Hope this helps someone. Happy coding!