Class variables vs class level instance variables

Question

Consider this code:

class Polygon
  @sides=1
  @@sides = 10
  class << self; attr_accessor :sides end
  def self.sides
    @@sides
  end
end

If I print sides:

p Polygon.sides

I get 10. If I change the order of class and self.sides, I will get 1. What is the cause of this behaviour? How can I call the @@sides or @sides independently of the order of the methods?

edit

I found this excellent post that discuss the difference between class variables, class instance variables and instance variables.

steenslag · Accepted Answer · 2015-03-08 21:21:11Z

0

class << self; attr_accessor :sides end

is equivalent to:

def self.sides
  @sides
end

def self.sides=(arg)
  @sides = arg
end

This sidesmethod then gets overwritten. Use two methods (with different names) to access both variables (or put them in an array and return that in a method).

edited Mar 8, 2015 at 21:21

answered Mar 8, 2015 at 16:22

steenslag

80.2k16 gold badges144 silver badges174 bronze badges

Sign up to request clarification or add additional context in comments.

Collectives™ on Stack Overflow

Class variables vs class level instance variables

1 Answer 1

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

Comments

Your Answer

Sign up or log in

Post as a guest

Related