adds some details to the rationale of converted_arrays [ci skip]

1 files changed, 4 insertions, 0 deletions

diff --git a/actionpack/lib/action_controller/metal/strong_parameters.rb b/actionpack/lib/action_controller/metal/strong_parameters.rb
index 55954d0f37..c3c3e4c4f1 100644
--- a/actionpack/lib/action_controller/metal/strong_parameters.rb
+++ b/actionpack/lib/action_controller/metal/strong_parameters.rb
@@ -129,6 +129,10 @@ module ActionController
     # Attribute that keeps track of converted arrays, if any, to avoid double
     # looping in the common use case permit + mass-assignment. Defined in a
     # method to instantiate it only if needed.
+    #
+    # Testing membership still loops, but it's going to be faster than our own
+    # loop that converts values. Also, we are not going to build a new array
+    # object per fetch.
     def converted_arrays
       @converted_arrays ||= Set.new
     end