1 files changed, 22 insertions, 26 deletions

diff --git a/actionpack/lib/action_controller/metal/strong_parameters.rb b/actionpack/lib/action_controller/metal/strong_parameters.rb
index 4c979ad4ec..06d625e4d5 100644
--- a/actionpack/lib/action_controller/metal/strong_parameters.rb
+++ b/actionpack/lib/action_controller/metal/strong_parameters.rb
@@ -540,6 +540,10 @@ module ActionController
         @permitted = new_permitted
       end
 
+      def fields_for_style?
+        @parameters.all? { |k, v| k =~ /\A-?\d+\z/ && v.is_a?(Hash) }
+      end
+
     private
       def new_instance_with_inherited_permitted_status(hash)
         self.class.new(hash).tap do |new_instance|
@@ -566,22 +570,20 @@ module ActionController
       end
 
       def each_element(object)
-        if object.is_a?(Array)
-          object.map { |el| yield el }.compact
-        elsif fields_for_style?(object)
-          hash = object.class.new
-          object.each { |k,v| hash[k] = yield v }
-          hash
-        else
-          yield object
+        case object
+        when Array
+          object.grep(Parameters).map { |el| yield el }.compact
+        when Parameters
+          if object.fields_for_style?
+            hash = object.class.new
+            object.each { |k,v| hash[k] = yield v }
+            hash
+          else
+            yield object
+          end
         end
       end
 
-      def fields_for_style?(object)
-        (object.is_a?(Hash) || object.is_a?(Parameters)) &&
-          object.to_unsafe_h.all? { |k, v| k =~ /\A-?\d+\z/ && v.is_a?(Hash) }
-      end
-
       def unpermitted_parameters!(params)
         unpermitted_keys = unpermitted_keys(params)
         if unpermitted_keys.any?
@@ -643,14 +645,8 @@ module ActionController
       end
 
       def array_of_permitted_scalars?(value)
-        if value.is_a?(Array)
-          value.all? {|element| permitted_scalar?(element)}
-        end
-      end
-
-      def array_of_permitted_scalars_filter(params, key)
-        if has_key?(key) && array_of_permitted_scalars?(self[key])
-          params[key] = self[key]
+        if value.is_a?(Array) && value.all? {|element| permitted_scalar?(element)}
+          yield value
         end
       end
 
@@ -661,17 +657,17 @@ module ActionController
         # Slicing filters out non-declared keys.
         slice(*filter.keys).each do |key, value|
           next unless value
+          next unless has_key? key
 
           if filter[key] == EMPTY_ARRAY
             # Declaration { comment_ids: [] }.
-            array_of_permitted_scalars_filter(params, key)
+            array_of_permitted_scalars?(self[key]) do |val|
+              params[key] = val
+            end
           else
             # Declaration { user: :name } or { user: [:name, :age, { address: ... }] }.
             params[key] = each_element(value) do |element|
-              if element.is_a?(Hash) || element.is_a?(Parameters)
-                element = self.class.new(element) unless element.respond_to?(:permit)
-                element.permit(*Array.wrap(filter[key]))
-              end
+              element.permit(*Array.wrap(filter[key]))
             end
           end
         end