Adds `not_in?` onto Object

2 files changed, 16 insertions, 0 deletions

diff --git a/activesupport/lib/active_support/core_ext/object.rb b/activesupport/lib/active_support/core_ext/object.rb
index f4f9152d6a..a2c5a472f5 100644
--- a/activesupport/lib/active_support/core_ext/object.rb
+++ b/activesupport/lib/active_support/core_ext/object.rb
@@ -4,6 +4,7 @@ require 'active_support/core_ext/object/duplicable'
 require 'active_support/core_ext/object/deep_dup'
 require 'active_support/core_ext/object/try'
 require 'active_support/core_ext/object/inclusion'
+require 'active_support/core_ext/object/exclusion'
 
 require 'active_support/core_ext/object/conversions'
 require 'active_support/core_ext/object/instance_variables'
diff --git a/activesupport/lib/active_support/core_ext/object/exclusion.rb b/activesupport/lib/active_support/core_ext/object/exclusion.rb
new file mode 100644
index 0000000000..58dfb649e5
--- /dev/null
+++ b/activesupport/lib/active_support/core_ext/object/exclusion.rb
@@ -0,0 +1,15 @@
+class Object
+  # Returns true if this object is excluded in the argument. Argument must be
+  # any object which responds to +#include?+. Usage:
+  #
+  #   characters = ["Konata", "Kagami", "Tsukasa"]
+  #   "MoshiMoshi".not_in?(characters) # => true
+  #
+  # This will throw an +ArgumentError+ if the argument doesn't respond
+  # to +#include?+.
+  def not_in?(another_object)
+    !another_object.include?(self)
+  rescue NoMethodError
+    raise ArgumentError.new("The parameter passed to #not_in? must respond to #include?")
+  end
+end
\ No newline at end of file