Add 'Hash#deep_transform_values', and 'Hash#deep_transform_values!'

2 files changed, 53 insertions, 0 deletions

diff --git a/activesupport/lib/active_support/core_ext/hash.rb b/activesupport/lib/active_support/core_ext/hash.rb
index c4b9e5f1a0..2f0901d853 100644
--- a/activesupport/lib/active_support/core_ext/hash.rb
+++ b/activesupport/lib/active_support/core_ext/hash.rb
@@ -2,6 +2,7 @@
 
 require "active_support/core_ext/hash/conversions"
 require "active_support/core_ext/hash/deep_merge"
+require "active_support/core_ext/hash/deep_transform_values"
 require "active_support/core_ext/hash/except"
 require "active_support/core_ext/hash/indifferent_access"
 require "active_support/core_ext/hash/keys"
diff --git a/activesupport/lib/active_support/core_ext/hash/deep_transform_values.rb b/activesupport/lib/active_support/core_ext/hash/deep_transform_values.rb
new file mode 100644
index 0000000000..ab68c34309
--- /dev/null
+++ b/activesupport/lib/active_support/core_ext/hash/deep_transform_values.rb
@@ -0,0 +1,52 @@
+# frozen_string_literal: true
+
+class Hash
+  # Returns a new hash with all keys converted by the block operation.
+  # This includes the keys from the root hash and from all
+  # nested hashes and arrays.
+  #
+  #  hash = { person: { name: 'Rob', age: '28' } }
+  #
+  #  hash.deep_transform_values{ |value| value.to_s.upcase }
+  #  # => {person: {name: "ROB", age: "28"}}
+  def deep_transform_values(&block)
+    _deep_transform_values_in_object(self, &block)
+  end
+
+  # Destructively converts all values by using the block operation.
+  # This includes the values from the root hash and from all
+  # nested hashes and arrays.
+  def deep_transform_values!(&block)
+    _deep_transform_values_in_object!(self, &block)
+  end
+
+  private
+    # support methods for deep transforming nested hashes and arrays
+    def _deep_transform_values_in_object(object, &block)
+      case object
+      when Hash
+        object.each_with_object({}) do |(key, value), result|
+          result[key] = _deep_transform_values_in_object(value, &block)
+        end
+      when Array
+        object.map { |e| _deep_transform_values_in_object(e, &block) }
+      else
+        yield(object)
+      end
+    end
+
+    def _deep_transform_values_in_object!(object, &block)
+      case object
+      when Hash
+        object.keys.each do |key|
+          value = object.delete(key)
+          object[key] = _deep_transform_values_in_object!(value, &block)
+        end
+        object
+      when Array
+        object.map! { |e| _deep_transform_values_in_object!(e, &block) }
+      else
+        yield(object)
+      end
+    end
+end