[Ruby]How to create singleton class ?

標籤：singleton   design pattern   instance   ruby   

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()