variables in ruby

ruby_vars.rb

class A

  @@class_var = 'aclassvar'
  @class_instance_var = 'aclassinstancevar'

  def initialize
    @instance_var = 'ainstance_var'
  end
  
  def A.class_method
    puts "value of @@class_var: #{@@class_var}"
    puts "value of @class_instance_var: #{@class_instance_var}"
    puts "value of @instance_var: #{@instance_var}"
  end

  def a_method
    puts "value of @@class_var: #{@@class_var}"
    puts "value of @class_instance_var: #{@class_instance_var}"
    puts "value of @instance_var: #{@instance_var}"
  end
end

puts "\n\nNo instances of A - call class_method...\n\n"
A.class_method
a = A.new
puts "\n\n1 instancesof A - call a_method...\n\n"
a.a_method


class B < A

  @@class_var = 'bclassvar'
  @class_instance_var = 'bclassinstancevar'

  def initialize
    @instance_var = 'binstance_var'
  end
  
  def B.class_method
    puts "value of @@class_var: #{@@class_var}"
    puts "value of @class_instance_var: #{@class_instance_var}"
    puts "value of @instance_var: #{@instance_var}"
  end

  def b_method
    puts "value of @@class_var: #{@@class_var}"
    puts "value of @class_instance_var: #{@class_instance_var}"
    puts "value of @instance_var: #{@instance_var}"
  end
end

puts "\n\nNo instances of B - call class_method..\n\n."
B.class_method
b = B.new
puts "\n\n1 instancesof B - call b_method...\n\n"
b.b_method


puts "\n\nCalling A.class_method again, see how the class variable is shared accross the inheritance heirachy but the class instance variable is truly static per class...\n\n"
A.class_method