Ruby class instance methods and instance methods with instance variables example (irc).

example.rb

class MyApp
  class << self
    attr_accessor :version
  end

  attr_accessor :version
end

MyApp.version

app = MyApp.new
app.version

MyApp.version = 'class 0.0.0'
MyApp.version

app.version
app.version = 'instance 1.1.1'
app.version

MyApp.version

class MyApp
  VERSION = '1.2.3'.freeze

  def version
    VERSION
  end
end

MyApp::VERSION
app = MyApp.new
app.version