Add Hash#transform_keys and Hash#transform_keys! and refactor *_keys methods to use them.

3 files changed, 42 insertions, 18 deletions

diff --git a/activesupport/CHANGELOG.md b/activesupport/CHANGELOG.md
index dace2f81f5..b2bacde799 100644
--- a/activesupport/CHANGELOG.md
+++ b/activesupport/CHANGELOG.md
@@ -1,5 +1,7 @@
 ## Rails 4.0.0 (unreleased) ##
 
+*   Add `Hash#transform_keys` and `Hash#transform_keys!`. *Mark McSpadden*
+
 *   Changed xml type `datetime` to `dateTime` (with upper case letter `T`). *Angelo Capilleri*  
 
 *   Add `:instance_accessor` option for `class_attribute`. *Alexey Vakhov*
diff --git a/activesupport/lib/active_support/core_ext/hash/keys.rb b/activesupport/lib/active_support/core_ext/hash/keys.rb
index be4d611ce7..8b24ef3350 100644
--- a/activesupport/lib/active_support/core_ext/hash/keys.rb
+++ b/activesupport/lib/active_support/core_ext/hash/keys.rb
@@ -1,46 +1,53 @@
 class Hash
-  # Return a new hash with all keys converted to strings.
+  # Return a new hash with all keys converted using the block operation.
   #
-  #   { :name => 'Rob', :years => '28' }.stringify_keys
-  #   #=> { "name" => "Rob", "years" => "28" }
-  def stringify_keys
+  #  { :name => 'Rob', :years => '28' }.transform_keys{ |key| key.to_s.upcase }
+  #  # => { "NAME" => "Rob", "YEARS" => "28" }
+  def transform_keys
     result = {}
     keys.each do |key|
-      result[key.to_s] = self[key]
+      result[yield(key)] = self[key]
     end
     result
   end
 
-  # Destructively convert all keys to strings. Same as
-  # +stringify_keys+, but modifies +self+.
-  def stringify_keys!
+  # Destructively convert all keys using the block operations.
+  # Same as transform_keys but modifies +self+
+  def transform_keys!
     keys.each do |key|
-      self[key.to_s] = delete(key)
+      self[yield(key)] = delete(key)
     end
     self
   end
 
+  # Return a new hash with all keys converted to strings.
+  #
+  #   { :name => 'Rob', :years => '28' }.stringify_keys
+  #   #=> { "name" => "Rob", "years" => "28" }
+  def stringify_keys
+    transform_keys{ |key| key.to_s }
+  end
+
+  # Destructively convert all keys to strings. Same as
+  # +stringify_keys+, but modifies +self+.
+  def stringify_keys!
+    transform_keys!{ |key| key.to_s }
+  end
+
   # Return a new hash with all keys converted to symbols, as long as
   # they respond to +to_sym+.
   #
   #   { 'name' => 'Rob', 'years' => '28' }.symbolize_keys
   #   #=> { :name => "Rob", :years => "28" }
   def symbolize_keys
-    result = {}
-    keys.each do |key|
-      result[(key.to_sym rescue key)] = self[key]
-    end
-    result
+    transform_keys{ |key| key.to_sym rescue key }
   end
   alias_method :to_options,  :symbolize_keys
 
   # Destructively convert all keys to symbols, as long as they respond
   # to +to_sym+. Same as +symbolize_keys+, but modifies +self+.
   def symbolize_keys!
-    keys.each do |key|
-      self[(key.to_sym rescue key)] = delete(key)
-    end
-    self
+    transform_keys!{ |key| key.to_sym rescue key }
   end
   alias_method :to_options!, :symbolize_keys!
 
diff --git a/activesupport/test/core_ext/hash_ext_test.rb b/activesupport/test/core_ext/hash_ext_test.rb
index 0b0e7da4a5..b13ee4c9ff 100644
--- a/activesupport/test/core_ext/hash_ext_test.rb
+++ b/activesupport/test/core_ext/hash_ext_test.rb
@@ -28,10 +28,13 @@ class HashExtTest < ActiveSupport::TestCase
     @mixed   = { :a  => 1, 'b' => 2 }
     @fixnums = {  0  => 1,  1  => 2 }
     @illegal_symbols = { [] => 3 }
+    @upcase_strings = { 'A' => 1, 'B' => 2 }
   end
 
   def test_methods
     h = {}
+    assert_respond_to h, :transform_keys
+    assert_respond_to h, :transform_keys!
     assert_respond_to h, :symbolize_keys
     assert_respond_to h, :symbolize_keys!
     assert_respond_to h, :stringify_keys
@@ -40,6 +43,18 @@ class HashExtTest < ActiveSupport::TestCase
     assert_respond_to h, :to_options!
   end
 
+  def test_transform_keys
+    assert_equal @upcase_strings, @strings.transform_keys{ |key| key.to_s.upcase }
+    assert_equal @upcase_strings, @symbols.transform_keys{ |key| key.to_s.upcase }
+    assert_equal @upcase_strings, @mixed.transform_keys{ |key| key.to_s.upcase }
+  end
+
+  def test_transform_keys!
+    assert_equal @upcase_strings, @symbols.dup.transform_keys!{ |key| key.to_s.upcase }
+    assert_equal @upcase_strings, @strings.dup.transform_keys!{ |key| key.to_s.upcase }
+    assert_equal @upcase_strings, @mixed.dup.transform_keys!{ |key| key.to_s.upcase }
+  end
+
   def test_symbolize_keys
     assert_equal @symbols, @symbols.symbolize_keys
     assert_equal @symbols, @strings.symbolize_keys