class/self Example

gistfile1.rb

module C
  class << self
    def f
    end
  end
end

module D
  def self.f
  end
end

puts "f is a C class method?: #{C.methods.include?('f') ? 'Yes' : 'No' }"
puts "f is a D class method?: #{D.methods.include?('f') ? 'Yes' : 'No' }"
puts

puts "C.singleton_methods = #{C.singleton_methods.join(', ')}"
puts "D.singleton_methods = #{D.singleton_methods.join(', ')}"
puts

s = 'foo'
class << s
  def twice
    self * 2
  end
end

puts "Call twice: #{s.twice}"
puts "s.singleton_methods = #{s.singleton_methods}"


=begin

Output is:

f is a C class method?: Yes
f is a D class method?: Yes

C.singleton_methods = f
D.singleton_methods = f

Call twice: foofoo
s.singleton_methods = twice

=end