From: William Paulson <billpaulson@...>
Date: 2012-06-10T05:40:05+09:00
Subject: Re: Class variables and self

On Jun 9, 2012, at 2:43 PM, Mike Glaz <lists@ruby-forum.com> wrote:

> I'm currently reading The Well-Grounded Rubyist.  In the section about
> class variables, instance variables, and self they have this class as an
> example:
> 
> class Car
>  @@makes = []
>  @@cars = {}
> 
>  attr_reader :make
> 
>  def self.total_count
>    @total_count || 0
>  end
> 
>  def self.total_count=(n)
>    @total_count = n
>  end
> 
>  def self.add_make(make)
>    unless @makes.include?(make)
>      @@makes << make
>      @@cars[make] = 0
>    end
>  end
> 
>  def initialize(make)
>    if @@makes.include?(make)
>      puts "Creating a new #{make}!"
>      @make = make
>      self.class.total_count += 1
>    else
>      raise "No such make: #{make}."
>    end
>  end
> 
>  def make_mates
>    @@cars[self.make]
>  end
> end
> 
> My question is in the initialize method about the line:
> 
>  self.class.total_count += 1
> 
> what is the purpose of the 'class' in that statement?
> 
Since total_count is a method of class Car, inside the initialize method of an instance you can refer to class Car as self.class. It would seem simpler to say Car::total_count in this particular case.