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 classes redefine the #class instance method, so I had to find another way to get the actual class; Let's say it's stored in variable "klass", and klass === object is true.
In Ruby 1.8 I could do this, assuming Object wasn't monkeypatched:
Object.instance_method(:class).bind(object).call
This worked for ActiveSupport::Duration instances:
# Ruby 1.8
# (tries to trick us)
20.seconds.class
=> Fixnum
# don't try to trick us, we can tell
Object.instance_method(:class).bind(20.seconds).call
=> ActiveSupport::Duration
But, in Ruby 1.9 this no longer works:
# Ruby 1.9
# we are not smart...
Object.instance_method(:class).bind(20.seconds).call
TypeError: bind argument must be an instance of Object
from (irb):53:in `bind'
from (irb):53
from /Users/user/.rvm/rubies/ruby-1.9.2-p0/bin/irb:17:in `<main>'
It turns out that ActiveSupport::Duration subclasses ActiveSupport::BasicObject. The latter is made to subclass ::BasicObject in Ruby 1.9, so Object is excluded from the inheritance chain. This doesn't, and can't, happen in Ruby 1.8, so ActiveSupport::BasicObject is a subclass of Object.
I haven't found any way to detect the actual class of a Ruby 1.9 object that isn't an instance of Object. BasicObject in 1.9 is really bare-bones:
BasicObject.instance_methods
=> [:==, :equal?, :!, :!=, :instance_eval, :instance_exec, :__send__]
Ideas?
UPDATE:
Since ruby 1.9 reached end-of-life, I'm changing my accept to @indirect's answer. The mentions of ruby 1.9 above are merely for historical purposes, to show that the change from 1.8 to 1.9 was the original cause of my problem.
If you can upgrade to Ruby 2.0, you don't need to implement anything at all:
>> Kernel.instance_method(:class).bind(BasicObject.new).call
=> BasicObject