to_prepare (ActionController::Dispatcher)

    # File lib/action_controller/dispatcher.rb, line 34
          def to_prepare(identifier = nil, &block)
            # Already registered: update the existing callback
            if identifier
              if callback = callbacks[:prepare].assoc(identifier)
                callback[1] = block
              else
                callbacks[:prepare] << [identifier, block]
              end
            else
              callbacks[:prepare] << block
            end
          end