Singleton is one design pattern in the software engineering. Ruby has its own special feature to declare singleton class. I will demonstrate two examples as below:
class Logger def initialize @log = File.open("log.txt", "a") end @@instance = Logger.new def self.instance return @@instance end def log(msg) @log.puts(msg) end private_class_method :newend Logger.instance.log('message 1')require "singleton"class Test include Singleton def idea puts "this is test" end def self.good puts "good idea" end endputs Test.good()puts Test.instance.idea()