1 files changed, 25 insertions, 2 deletions
diff --git a/actionpack/lib/action_controller/metal/strong_parameters.rb b/actionpack/lib/action_controller/metal/strong_parameters.rb
index a01110d474..64672de57e 100644
--- a/actionpack/lib/action_controller/metal/strong_parameters.rb
+++ b/actionpack/lib/action_controller/metal/strong_parameters.rb
@@ -184,6 +184,13 @@ module ActionController
     # Returns an unsafe, unfiltered
     # <tt>ActiveSupport::HashWithIndifferentAccess</tt> representation of this
     # parameter.
+    #
+    #   params = ActionController::Parameters.new({
+    #     name: 'Senjougahara Hitagi',
+    #     oddity: 'Heavy stone crab'
+    #   })
+    #   params.to_unsafe_h
+    #   # => {"name"=>"Senjougahara Hitagi", "oddity" => "Heavy stone crab"}
     def to_unsafe_h
       convert_parameters_to_hashes(@parameters, :to_unsafe_h)
     end
@@ -430,6 +437,21 @@ module ActionController
       )
     end
 
+    if Hash.method_defined?(:dig)
+      # Extracts the nested parameter from the given +keys+ by calling +dig+
+      # at each step. Returns +nil+ if any intermediate step is +nil+.
+      #
+      # params = ActionController::Parameters.new(foo: { bar: { baz: 1 } })
+      # params.dig(:foo, :bar, :baz) # => 1
+      # params.dig(:foo, :zot, :xyz) # => nil
+      #
+      # params2 = ActionController::Parameters.new(foo: [10, 11, 12])
+      # params2.dig(:foo, 1) # => 11
+      def dig(*keys)
+        convert_value_to_parameters(@parameters.dig(*keys))
+      end
+    end
+
     # Returns a new <tt>ActionController::Parameters</tt> instance that
     # includes only the given +keys+. If the given +keys+
     # don't exist, returns an empty hash.
@@ -799,7 +821,8 @@ module ActionController
   #   end
   #
   # In order to use <tt>accepts_nested_attributes_for</tt> with Strong \Parameters, you
-  # will need to specify which nested attributes should be whitelisted.
+  # will need to specify which nested attributes should be whitelisted. You might want
+  # to allow +:id+ and +:_destroy+, see ActiveRecord::NestedAttributes for more information.
   #
   #   class Person
   #     has_many :pets
@@ -819,7 +842,7 @@ module ActionController
   #         # It's mandatory to specify the nested attributes that should be whitelisted.
   #         # If you use `permit` with just the key that points to the nested attributes hash,
   #         # it will return an empty hash.
-  #         params.require(:person).permit(:name, :age, pets_attributes: [ :name, :category ])
+  #         params.require(:person).permit(:name, :age, pets_attributes: [ :id, :name, :category ])
   #       end
   #   end
   #