Add Enumerable#without

activesupport/CHANGELOG.md

+*   Added `#without` on `Enumerable` and `Array` to return a copy of an
+    enumerable without the specified elements.
+
+    *Todd Bealmear*
+
 *   Fixed a problem where String#truncate_words would get stuck with a complex
     string.
 

activesupport/lib/active_support/core_ext/array/grouping.rb

@@ -113,4 +113,16 @@ def split(value = nil)
       results
     end
   end
+
+  # Returns a copy of the Array without the specified elements.
+  #
+  #   people = ["David", "Rafael", "Aaron", "Todd"]
+  #   people.without "Aaron", "Todd"
+  #     => ["David", "Rafael"]
+  #
+  # Note: This is an optimization of `Enumerable#without` that uses `Array#-`
+  # instead of `Array#reject` for performance reasons.
+  def without(*elements)
+    self - elements
+  end
 end

activesupport/lib/active_support/core_ext/enumerable.rb

@@ -60,6 +60,17 @@ def many?
   def exclude?(object)
     !include?(object)
   end
+
+  # Returns a copy of the enumerable without the specified elements.
+  #
+  #   ["David", "Rafael", "Aaron", "Todd"].without "Aaron", "Todd"
+  #     => ["David", "Rafael"]
+  #
+  #   {foo: 1, bar: 2, baz: 3}.without :bar
+  #     => {foo: 1, baz: 3}
+  def without(*elements)
+    reject { |element| element.in?(elements) }
+  end
 end
 
 class Range #:nodoc:

activesupport/test/core_ext/enumerable_test.rb

@@ -103,4 +103,11 @@ def test_exclude?
     assert_equal true,  GenericEnumerable.new([ 1 ]).exclude?(2)
     assert_equal false, GenericEnumerable.new([ 1 ]).exclude?(1)
   end
+
+  def test_without
+    assert_equal [1, 2, 4], GenericEnumerable.new((1..5).to_a).without(3, 5)
+    assert_equal [1, 2, 4], (1..5).to_a.without(3, 5)
+    assert_equal [1, 2, 4], (1..5).to_set.without(3, 5)
+    assert_equal({foo: 1, baz: 3}, {foo: 1, bar: 2, baz: 3}.without(:bar))
+  end
 end

guides/source/active_support_core_extensions.md

@@ -2182,6 +2182,17 @@ to_visit << node if visited.exclude?(node)
 
 NOTE: Defined in `active_support/core_ext/enumerable.rb`.
 
+### `without`
+
+The method `without` returns a copy of an enumerable with the specified elements
+removed:
+
+```ruby
+people.without("Aaron", "Todd")
+```
+
+NOTE: Defined in `active_support/core_ext/enumerable.rb`.
+
 Extensions to `Array`
 ---------------------