for an object -- singleton class

class_self.rb

class MyClass
end

class << MyClass
  puts "self is #{self}"
end


# => self is #<Class:MyClass>

module_self.rb

module MyModule
end

class << MyModule
  puts "self is #{self}"
end

# => self is #<Class:MyModule>

MyClass.rb

class MyClass

  def my_instance_method
    puts "this is an instance method"
  end

  #self here is MyClass
  class << self
    def count_objects
      "counting objects..DONE"
    end
  end
end

#assigning self explicitly
class << MyClass
  def find_average
    "finding average..DONE"
  end
end


p MyClass.count_objects # => "counting objects..DONE"
p MyClass.find_average # => "finding average..DONE"

object_self.rb

class MyClass
end

my_object = MyClass.new

class << my_object
  puts "self is #{self}"
end

# => self is #<Class:#<MyClass:0x0000010086cf58>>