A monkeypatch on Object which adds the instance method in?, which is effectively the standard library Array#include? method with the subject and object inverted i.e. so the object you're search for receives the method call.


Add this line to your application's Gemfile:

gem 'object-in'

And then execute:

$ bundle

Or install it yourself as:

$ gem install object-in


This adds to Object, so it will be available on (essentially?) everything. It takes one parameter, the array you want to check for the object's inclusion in.

array = %w{yankee doodle doo}
"yankee".in? array # => true
"da".in? array # => false
yankee.in? array.join(" ") # => raises a TypeError exception
  • It returns true if the array passed in includes the object.
  • It returns false if the array passed in doesn't include the object.
  • It raises a TypeError exception if the passed in object isn't an Array


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