def tag_name(name, multiple = false, index = nil)
      sanitized_method_name = name.to_s.sub(/\?$/, "")

      case
      when @builder.object_name.empty?
        "#{sanitized_method_name}#{multiple ? "[]" : ""}"
      when index
        "#{@builder.object_name}[#{index}][#{sanitized_method_name}]#{multiple ? "[]" : ""}"
      else
        "#{@builder.object_name}[#{sanitized_method_name}]#{multiple ? "[]" : ""}"
      end
    end
def tag_name(name, multiple = false, index = nil)
      sanitized_method_name = name.to_s.sub(/\?$/, "")

      case
      when @builder.object_name.empty?
        "#{sanitized_method_name}#{multiple ? "[]" : ""}"
      when index
        "#{@builder.object_name}[#{index}][#{sanitized_method_name}]#{multiple ? "[]" : ""}"
      else
        "#{@builder.object_name}[#{sanitized_method_name}]#{multiple ? "[]" : ""}"
      end
    end
https://github.com/rails/rails/blob/master/actionview/lib/action_view/helpers/tags/base.rb#L108