A small library of missing ruby methods for introspection. See Usage.

Build Status Dependencies


Add this line to your application's Gemfile:

gem 'is_a'

And then execute:

$ bundle

Or install it yourself as:

$ gem install is_a



If you got an object via _id2ref or from similar place - do not rush to duck-typing, it may be a BasicObject and not respond to respond_to?. IsA aims in handling such cases.

require 'is_a'

obj =
  puts "Yep, BasicObject will not tell you it's class"
  cls = IsA.class_of(obj)
  puts "But IsA will. It's #{cls}"

IsA.object?(obj) # => false
IsA.object?("anything that is derived from Object") # => true

 #Also on 1.9.2 there's no way of getting object_id of BasicObject, here it is:
id = IsA.id_of(obj) # or alias ObjectSpace._ref2id(obj)
ObjectSpace._id2ref(id) == obj # => true
 #For 1.9.3 use BasicObject#__id__

Fast single line from caller

Ruby's caller is handy, but sometimes you do not need the whole array of strings it allocates generates on each call.

IsA.caller_line (also global caller_line) is a lot faster and does not mess your heap that lot (allocates just the result string, meaning fewer GC):

require 'is_a'
require 'benchmark'
n = 10000 do |x|"caller[1]") { n.times { caller[1] } }"caller_line") { n.times { caller_line(1) } }


                          user     system      total        real
caller[1]             1.760000   0.040000   1.800000 (  1.802799)
caller_line           0.080000   0.000000   0.080000 (  0.089649)


  1. Fork it
  2. Create your feature branch (git checkout -b my-new-feature)
  3. Commit your changes (git commit -am 'Added some feature')
  4. Push to the branch (git push origin my-new-feature)
  5. Create new Pull Request