Question

I’m reading a book about Ruby/Rails and have a question about something simple. In the method “turn” below, the author uses “self,” which refers to the class. However, what is the difference (in terms of what you can and cannot do), if any, if he left off “self” and just did

direction = new_direction

Code

class Car << ActiveRecord::Base

  validates :direction, :presence => true 
  validates :speed, :presence => true

  def turn(new_direction) 

    self.direction = new_direction

  end

end

Answer 1

ActiveRecord (persisted) vars must be accessed with self because of AR’s implementation.

Here, the self distinguishes a column (DB) variable from a “normal”, un-persisted instance property. The difference would be that the value wouldn’t be saved in the database on a save or update.