Added Object#present_in to simplify value whitelisting

3 files changed, 29 insertions, 0 deletions

diff --git a/activesupport/CHANGELOG.md b/activesupport/CHANGELOG.md
index f25172c15c..f4c8a4dd72 100644
--- a/activesupport/CHANGELOG.md
+++ b/activesupport/CHANGELOG.md
@@ -2,6 +2,18 @@
 
     *Xavier Noria*
 
+*   Added Object#present_in to simplify value whitelisting.
+
+    Before:
+    
+      params[:bucket_type].in?(%w( project calendar )) ? params[:bucket_type] : nil
+      
+    After:
+    
+      params[:bucket_type].present_in %w( project calendar )
+    
+    *DHH*
+
 *   Fix the implementation of Multibyte::Unicode.tidy_bytes for JRuby
 
     The existing implementation caused JRuby to raise the error:
diff --git a/activesupport/lib/active_support/core_ext/object/inclusion.rb b/activesupport/lib/active_support/core_ext/object/inclusion.rb
index b5671f66d0..141f19e7b3 100644
--- a/activesupport/lib/active_support/core_ext/object/inclusion.rb
+++ b/activesupport/lib/active_support/core_ext/object/inclusion.rb
@@ -12,4 +12,16 @@ class Object
   rescue NoMethodError
     raise ArgumentError.new("The parameter passed to #in? must respond to #include?")
   end
+
+  # Returns the receiver if it's included in the argument otherwise returns +nil+.
+  # Argument must be any object which responds to +#include?+. Usage:
+  #
+  #   params[:bucket_type].present_in %w( project calendar )
+  #
+  # This will throw an ArgumentError if the argument doesn't respond to +#include?+.
+  #
+  # @return [Object]
+  def present_in(another_object)
+    self.in?(another_object) ? self : nil
+  end
 end
diff --git a/activesupport/test/core_ext/object/inclusion_test.rb b/activesupport/test/core_ext/object/inclusion_test.rb
index 478706eeae..33f40b60b1 100644
--- a/activesupport/test/core_ext/object/inclusion_test.rb
+++ b/activesupport/test/core_ext/object/inclusion_test.rb
@@ -47,4 +47,9 @@ class InTest < ActiveSupport::TestCase
   def test_no_method_catching
     assert_raise(ArgumentError) { 1.in?(1) }
   end
+  
+  def test_present_in
+    assert_equal "stuff", "stuff".present_in(%w( lots of stuff ))
+    assert_not "stuff".present_in(%w( lots of crap ))
+  end
 end