How do I get the class of a BasicObject instance?

Question

I have a script that iterates using ObjectSpace#each_object with no args. Then it prints how many instances exist for each class.

I realized that some

Answer 1

This is my modification of @paon's answer:

Reasoning behind the changes:

• Method name doesn't clash with existing libs, e.g. the ActiveSupport::Duration instance behavior 2.seconds.class remains Fixnum.
• Since Object doesn't have its own __realclass__ method, we want to avoid allocating the eigenclass for those instances. @paon's original answer did this inherently by defining the class method name.

---

class BasicObject
  def __realclass__
    ::Object === self ?
      # Note: to be paranoid about Object instances, we could 
      # use Object.instance_method(:class).bind(s).call.
      self.class :
      (class << self; self end).superclass
  end
end

# test
require 'active_support/core_ext/integer'
require 'active_support/core_ext/numeric'

duration = 2.seconds
string = 'hello world'
p duration.class  # => Fixnum
p string.class    # => String
GC.start
p ObjectSpace.count_objects[:T_CLASS]  # => 566

# creates the eigenclass
p duration.__realclass__  # => ActiveSupport::Duration
p ObjectSpace.count_objects[:T_CLASS]  # => 567

# doesn't create the eigenclass
p string.__realclass__  # => String
p ObjectSpace.count_objects[:T_CLASS]  # => 567