Invoke proxy middleware behavior via public method

How?

##
# Okish.
#
module Plugins
  module CanHaveConnectedSteps
    class Middleware < MethodChainMiddleware
      intended_for :result, entity: :service

      def next(...)
        return chain.next(...) if entity.steps.none?

        entity.steps.each_evaluated_step do |step|
          step.save_outputs_in_organizer!

          # ...
        end

        entity.steps.result
      end
    end
  end
end

##
# Better.
#
module Plugins
  module CanHaveConnectedSteps
    class Middleware < MethodChainMiddleware
      intended_for :result, entity: :service

      def next(...)
        return chain.next(...) if entity.steps.none?

        entity.steps_result(...)
      end
    end
  end
end

module Plugins
  module CanHaveConnectedSteps
    module Concern
      include Support::Concern

      instance_methods do
        def steps_result
          # ...

          steps.each_evaluated_step do |step|
            step.save_outputs_in_organizer!

            # ...
          end

          steps.result
        end

        # ...
      end
    end
  end
end

Why?

• It allows end-users to create middlewares specifically for proxy middleware behavior. For example:

  ##
  # Good.
  #
  class Service
    include ConvenientService::Standard::Config
  
    middlewares :steps_result do
      # ...
    end
  
    # ...
  end

• It decreases the amount of type checks.

  Without the extracted method, the end-user requries to utilize type checks to distinguish return values.

  ##
  # Bad.
  #
  class Middleware < MethodChainMiddleware
    intended_for :result, entity: :service
  
    def next(...)
      result = chain.next(...)
  
      if result.from_step? # Type check.
        some_logic_with(result)
      else
        # ...
      end
    end
  end

  ##
  # Better.
  #
  class Middleware < MethodChainMiddleware
    intended_for :step_result, entity: :service
  
    def next(...)
      result = chain.next(...)
  
      some_logic_with(result)
    end
  end

• It decreases the amount of order-dependent middlewares.

• It simplifies specs. Methods are easier to tests than middlewares.

Why not?

• When proxy middleware behavior is truly private.