Newbie question - self.var OR @var in ActiveRecord

I started learning rails by following the agile way. It comes to the
point where it puzzles me.

class Puzzle < ActiveRecord::Base

  # virtual var, not existing in the database
  def var
    @var
  end

  def var=(foo)
    @var= foo
    @var_in_database = @var + 1 # var_in_database exists in database
  end

end

Then when I do a save of this model it does nothing. I know that if I
instead put self.var_in_database it would work perfectly, but from my
limited knowledge of ruby @var should be working like self.var in most
cases. Now it is the rare case but I can't find the reason why this
doesn't work.

Please solve my puzzle, thank you.

The answer is easy - @var and self.var are not the same. All
variables in Ruby (it's a Ruby question, not Rails) are private and
you can never make them public directly. What is usually done is
creating getters and seters with the same name. Like this

class Foo
  def var
    @var
  end

  def var=(v)
    @var = v
  end
end

or like this (which does he same for you):

class Foo
  attr_acessor :var
end

So when you are talking about ActiveRecord objects, you must use
self.var, to call the magic methods created for you by ActiveRecord.

Cheers,
Yuri

All variables in Ruby (it's a Ruby question, not Rails) are private

I meant all object variables here