Question

In the Michael Hartl tutorial, chapter 8, we set up the sign in page and create a new column in the database to hold a base 64 string. In the tutorial it’s called a remember_token. In the user.rb:

  private

    def create_remember_token
        self.remember_token = SecureRandom.urlsafe_base64
    end

self has a property called remember_token? Is this already built in or did it get created elsewhere? Maybe I’m just not understanding this very well.

He writes:

Because of the way Active Record synthesizes attributes based on
database columns, without self the assignment would create a local
variable called remember_token, which isn’t what we want at all. Using
self ensures that assignment sets the user’s remember_token so that it
will be written to the database along with the other attributes when
the user is saved.

I’m confused, how did the user get a remember token? How does it know to write this to the database in that particular column?

In the user.rb you have the following code:

attr_accessible :name, :email, :password, :password_confirmation

There’s nothing about remember_token there. How does it know to include this at User.save?

Answer 1

In this context, self is a User object, and it has a remember_token attribute because of the database column created by the migration in Section 8.2.1 of the Ruby on Rails Tutorial. (Prepending self is necessary to assign to the attribute; without self, Ruby would just create a local variable called remember_token.)