Paul Bernhard

How come the mail and inbound_mail objects are available to all instance methods?

This question is not only related to ActionMailbox, but i will still post it here as i never saw a similar use of "local variables" before your episode on ActionMailbox, altough i am not sure if those are actually "local variables".

In your replies_mailbox.rb you have the following code:

class RepliesMailbox < ApplicationMailbox
  def process
    return if user.nil?
  end

  def user
    @user =|| User.find_by(email: mail.from)
        # the mail object is available here
  end

# …
end

Somehow the mail and the inbound_mail objects seem to be available to all instance methods of RepliesMailbox. This is an interesting functionality because you don't have to define all methods like def user(mail), def discussion(mail), def discussion_id(mail), if they all refer to the same mail object anyway.

I am not sure if the mail and inbound_mail are actually "local variables" and maybe i am missing out on a fundamental knowledge of variable scope. But how come you can access those objects throughout all methods? Can this way of "reusing" variables be used in all Ruby / Rails code?