Ruby Arrays don’t always have the correct datatypes for your application to execute correctly. The following method will confirm all your array :symbols will come out as strings. def array_to_s(array) array.map(&:to_s) end   >> array_to_s([:flexible, :moderate, "strict"]) => ["flexible", "moderate", "strict"] :)

This has been written about with the release of Rails 4, but this example might help those who are reading here and haven’t encountered the issue yet. Using strong parameters in Rails 4 if you have nested parameters the following syntax will help whitelist your params. def post_params params.require(:activity).permit( :source, :user_id, :body, content: [:title, :image_url, :excerpt] ) end :)