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

The following solution refers to the superclass of the eigenclass. As a consequence, it has the side effect of allocating the eigenclass (detectable by ObjectSpace.count_objects[:T_CLASS] in MRI). But since BasicObject#class is only invoked on blank slate objects (i.e. objects that are not kind-of Object, i.e. that are not Objects) the side effect also applies just for blank slate objects. For Objects, the standard Kernel#class is invoked.

class BasicObject
  def class
    (class << self; self end).superclass
  end
end

# tests:
puts RUBY_VERSION               # 1.9.2
class B < BasicObject; end
class X;               end
p BasicObject.new.class             # BasicObject
p B          .new.class             # B
p X          .new.class             # X
p               6.class             # Fixnum
p B.instance_method(:class).owner   # BasicObject
p X.instance_method(:class).owner   # Kernel
p          6.method(:class).owner   # Kernel

Edit - Note: Indeed, there is an issue with ActiveSupport::Duration. This class uses interception (method_missing) for redirecting messages to the :value attribute. As a consequence, it provides false introspection for its instances. To preserve this falsity, it is necessary to use another name for the class map, e.g. the proposed __realclass__. Thus, the modified solution might look like this:

class BasicObject
  def __realclass__; (class << self; self end).superclass end
end
class Object; alias __realclass__ class end

Another way of not invoking class << self on Objects is via Module#===, as suggested by Kelvin on this page.