Merge pull request #5287 from nashby/hash-slice-extract

refactor Hash#slice and Hash#extract!

activesupport/lib/active_support/core_ext/hash/slice.rb

@@ -13,17 +13,15 @@ class Hash
   #   valid_keys = [:mass, :velocity, :time]
   #   search(options.slice(*valid_keys))
   def slice(*keys)
-    keys = keys.map! { |key| convert_key(key) } if respond_to?(:convert_key)
-    hash = self.class.new
-    keys.each { |k| hash[k] = self[k] if has_key?(k) }
-    hash
+    keys.map! { |key| convert_key(key) } if respond_to?(:convert_key)
+    keys.each_with_object(self.class.new) { |k, hash| hash[k] = self[k] if has_key?(k) }
   end
 
   # Replaces the hash with only the given keys.
   # Returns a hash contained the removed key/value pairs
   #   {:a => 1, :b => 2, :c => 3, :d => 4}.slice!(:a, :b) # => {:c => 3, :d => 4}
   def slice!(*keys)
-    keys = keys.map! { |key| convert_key(key) } if respond_to?(:convert_key)
+    keys.map! { |key| convert_key(key) } if respond_to?(:convert_key)
     omit = slice(*self.keys - keys)
     hash = slice(*keys)
     replace(hash)
@@ -33,8 +31,6 @@ class Hash
   # Removes and returns the key/value pairs matching the given keys.
   #   {:a => 1, :b => 2, :c => 3, :d => 4}.extract!(:a, :b) # => {:a => 1, :b => 2}
   def extract!(*keys)
-    result = {}
-    keys.each {|key| result[key] = delete(key) }
-    result
+    keys.each_with_object({}) {|key, result| result[key] = delete(key) }
   end
 end

activesupport/test/core_ext/hash_ext_test.rb

@@ -486,6 +486,13 @@ class HashExtTest < ActiveSupport::TestCase
     assert_equal 'bender', slice['login']
   end
 
+  def test_extract
+    original = {:a => 1, :b => 2, :c => 3, :d => 4}
+    expected = {:a => 1, :b => 2}
+
+    assert_equal expected, {:a => 1, :b => 2, :c => 3, :d => 4}.extract!(:a, :b)
+  end
+
   def test_except
     original = { :a => 'x', :b => 'y', :c => 10 }
     expected = { :a => 'x', :b => 'y' }