basic null object

null_object.rb

# from http://avdi.org/talks/confident-code-rubymidwest-2011/confident-code.html

class NullObject
  def method_missing(*)
    self
  end

  def nil?
    true
  end
end

def Maybe(value)
  value.nil? ? NullObject.new : value
end

class SomeClass
  def initialize(logger = NullObject.new)
    @logger = logger
  end
end

The basic idea is nil is over used. It means error or missing data or flag for default behavior or uninitialized variable or default return value for some methods.