Ruby on Rails – Rails Generators for Subscription and Payment Processing

The idea was put up in rails best practices: Replace instance variable with local variable

Basically if you don't use many partials or have a single plain view for each controller method just using the instance variables in the view wouldn't really cause any trouble.

Nevertheless, if you use many partials and therefore have many instance variables declared in your controller..., it might be less confusing if you use the alternative of passing the controller (instance)-variable to the partials explicitly. That way - while working in the partial VIEW - you have one explicit reference to the variable/object you want to work with that is not shared with 'all' partials that are included in the creation of the page.

After all, you can handle this just as you like to handle it, noone will tell you to do it otherwise. My personal view, however, is that I like the idea of having explicitly references in my partials/views that can not be confused with other variables.

You're currently working on the User model within ruby as you look down you code you can see

def function

end

That creates a function that exists within the User class, so in theory from most anywhere else in your application you could do User.some_function, you only use self.some_function from within the class.

There isn't any difference between using User.encrypt and self.encrypt except that its safer, self.function means only look inside the current class.

I think you're probably getting attributes and functions mixed up because you're not seeing the () at the end of function calls, you don't actually use those in ruby unless you passing parameters to the function.

Where you're mentioning username, password, email etc those are fields associated with the database and are attributes.

The concept to understand here is that the User model represents the association with the underlying database, you can(as you have there) add extra functionality to ensure the quality of the data going in for example:

before_create :create_remember_token

That means that if ANYWHERE within you application you create a new user the model calls that function as part of the process of creating the record. Essentially by building functionality into models you can ensure that all data going into the database is treated in the same way.