Using rails like mvc pattern in a ruby gem

Question

I am creating a gem that has some model, controller and view components in it. I need to emulate a rails like mvc pattern for it. There are two options that come to my mind and I need to choose one of them. The following code is a simpler extraction of the problem.

Pattern1

project/model.rb

module Application
  module Namespace
    class Model
      def name
        'Mr. Model'
      end
    end
  end
end

project/controller.rb

module Application
  module Namespace
    class Controller
      def action
        Model.new.name
      end
    end
  end
end

project/application.rb

require_relative 'controller'
require_relative 'model'

module Application
  class Runner
    def run
      Namespace::Controller.new.action
    end
  end
end

Pattern2

project/model.rb

class Model
  def name
    'Mr. Model'
  end
end

project/controller.rb

class Controller
  def action
    Model.new.name
  end
end

project/application.rb

module Application
  module Namespace
    module_eval File.read(File.expand_path '../controller.rb', __FILE__)
    module_eval File.read(File.expand_path '../model.rb', __FILE__)
  end

  class Runner
    def run
      Namespace::Controller.new.action
    end
  end
end

irb(main):001:0> require 'project/application' 
=> true
irb(main):002:0> Application::Runner.new.run
=> "Mr. Model"

Both patterns include the models and controllers under a namespace, but with the pattern1 whenever I add new files, I will have to duplicate the ugly modular nesting. The pattern2 creates cleaner models and controllers with some extra magic being done in the application.

I would like some suggestions on these approaches or if there are better solutions to the problem. Questions like why a mvc pattern is needed anyways will be complicated to answer. Lets assume that a mvc pattern is needed and try to answer whats the cleanest way to emulate it.

EDIT:

On further thoughts, Rails uses subclasses. So we have a third pattern now.

Pattern3

project/application_controller.rb

module Application
  module Namespace
    class ApplicationController
    end
  end
end

project/active_model.rb

module Application
  module Namespace
    class ActiveModel
    end
  end
end

project/model.rb

class Model < Application::Namespace::ActiveModel
  def name
    'Mr. Model'
  end
end

project/controller.rb

class Controller < Application::Namespace::ApplicationController
  def action
    Model.new.name
  end
end

project/application.rb

module Application
  require_relative 'active_model'
  require_relative 'application_controller'
  require_relative 'controller'
  require_relative 'model'

  class Runner
    def run
      Controller.new.action
    end
  end
end

Still looking for some brighter ideas.

Not an answer, just two cents: the explicit module nesting per file can be really helpful and makes the code self–documenting. I really value code that explains itself. — piersadrian
– piersadrian, Commented Mar 20, 2013 at 6:36

Sergio Tulentsev · Accepted Answer · 2013-03-20 07:51:39Z

2

FWIW, you can rewrite this

module Application
  module Namespace
    class Model
      def name
        'Mr. Model'
      end
    end
  end
end

into this

# do this once
module Application
  module Namespace
  end
end

class Application::Namespace::Model
  def name
    'Mr. Model'
  end
end

Doesn't it remove subjective "ugliness"?

answered Mar 20, 2013 at 7:51

Sergio Tulentsev

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3 Comments

Alex Over a year ago

That does look better. I am however now more inclined towards pattern3.

Alex Over a year ago

I didn't realize that pattern3 is placing my models under the global namespace. I am going with your answer. I just need one other clarification. Why do all gems have that nested pattern? Does the community in general find it more clearer?

Sergio Tulentsev Over a year ago

@Alex: some of that probably stems from how code is physically organized into files/folders, but yeah, logical grouping with modules does more good than harm.

konyak · Accepted Answer · 2019-11-25 22:43:10Z

0

It may be better to use Rails engines in this case. It will namespace things properly for you.

https://guides.rubyonrails.org/engines.html

answered Nov 25, 2019 at 22:43

konyak

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