Namespacing

Learning Goals

• Why/when do we namespace our routes?
• What is the difference between Namespacing and Scoping?
• When would we use one over the other?

Exercise

Background

Read this section of the Rails docs about namespacing in Rails.

At a high level, namespacing a route in Rails does three things:

1. Allows us to put the controller for a resource into a directory inside of our controllers directory.
2. Changes the route that a user would visit.
3. Changes the prefix that we would use as a path helper.

Rails also allows us to do each of these three things independently:

1. module allows us to put the controller into a sub-directory.
2. scope changes the route that a user would visit.
3. as allows us to change the prefix we use as a path helper.

Let’s explore this functionality in a new project, first individually, then all together as a namespace.

Setup

Let’s create an app for CRUDding some cats. Yes, it sounds weird. Yes, it is weird. Weird is good.

rails new cats -T -d="postgresql" --skip-spring --skip-turbolinks

Routes Recap:

Let’s add some routes to our routes.rb for cats that will show all cats, show one cat, delete a cat, and edit a cat.

    get '/cats', to: 'cats#index'
    get '/cats/:id', to: 'cats#show'
    patch '/cats', to: 'cats#update'
    get '/cats/edit', to: 'cats#edit'
    delete '/cats/:id', to: 'cats#destroy'

At this point, when we run rake routes, we get the following:

   Prefix Verb   URI Pattern          Controller#Action
     cats GET    /cats(.:format)      cats#index
          GET    /cats/:id(.:format)  cats#show
          PATCH  /cats(.:format)      cats#update
cats_edit GET    /cats/edit(.:format) cats#edit
          DELETE /cats/:id(.:format)  cats#destroy

Distinguishing Routes

Let’s say we have:

• cats
• administrators

We want a way to distinguish your routes so an admin has additional functionality/control over your application.

For example, say we want http://localhost:3000/admin/cats to show edit/delete buttons for each individual cat and only admins can get here.

We also want http://localhost:3000/cats to show a list of cats (and anyone visiting our application can get here).

What can we do?

Scope

	# config/routes.rb
        get '/cats', to: 'cats#index'
        get '/cats/:id', to: 'cats#show'
	scope :admin do
	      patch '/cats', to: 'cats#update'
   	      get '/cats/edit', to: 'cats#edit'
    	      delete '/cats/:id', to: 'cats#destroy'
	end

Adding scope to our routes gives us the following when we run rake routes:

   Prefix Verb   URI Pattern                Controller#Action
     cats GET    /cats(.:format)            cats#index
          GET    /cats/:id(.:format)        cats#show
          PATCH  /admin/cats(.:format)      cats#update
cats_edit GET    /admin/cats/edit(.:format) cats#edit
          DELETE /admin/cats/:id(.:format)  cats#destroy

Potential Problems with scope

We’re going to need a way to differentiate our controllers. We want what we already have (the url prefix) AND a separate controller to encapsulate the different functionality.

We want both /admin/cats and /cats to be handled by our controllers in different ways.

Scope and Module

	get '/cats', to: 'cats#index'
        get '/cats/:id', to: 'cats#show'
	scope :admin, module: :admin do
	 patch '/cats', to: 'cats#update'
   	 get '/cats/edit', to: 'cats#edit'
    	 delete '/cats/:id', to: 'cats#destroy'
	end

If we have scope with module in our routes, we will get the following rake routes output:

     cats GET    /cats(.:format)            cats#index
          GET    /cats/:id(.:format)        cats#show
          PATCH  /admin/cats(.:format)      admin/cats#update
cats_edit GET    /admin/cats/edit(.:format) admin/cats#edit
          DELETE /admin/cats/:id(.:format)  admin/cats#destroy

By using module, Rails looks for our controller in a different place.

	# When we hit "http://localhost3000/admin/cats"

	# app/controllers/admin/cats_controller.rb
	class Admin::CatsController < ApplicationController
 	 def index
	  @cats = Cat.all
	 end
	end

What does that :: (scope resolution operator) remind us of?

Note: Where do you think Rails will look for this view template? It will look in the views/admin/cats folder.

Recap

• What have we done so far to our routes?
• What did module change for us?
• Do you notice anything missing when you run rake routes?

As you may have noticed, we don’t have any path helpers that are specific to this “special” admin prefix. Again, Rails can help us out with this.

scope, module and as

	get '/cats', to: 'cats#index'
    	get '/cats/:id', to: 'cats#show'
	scope :admin, module: :admin, as: :admin do
         patch '/cats', to: 'cats#update'
   	 get '/cats/edit', to: 'cats#edit'
    	 delete '/cats/:id', to: 'cats#destroy'
	end

Let’s run rake routes once again!

         Prefix Verb   URI Pattern                Controller#Action
           cats GET    /cats(.:format)            cats#index
                GET    /cats/:id(.:format)        cats#show
     admin_cats PATCH  /admin/cats(.:format)      admin/cats#update
admin_cats_edit GET    /admin/cats/edit(.:format) admin/cats#edit
          admin DELETE /admin/cats/:id(.:format)  admin/cats#destroy

So what does using scope, module, and as provide for us?

• path helpers via the prefix (admin_cats_path)
• controller prefix (Admin::CatsController) for more organization
• url prefix for user’s to see in their browser (http://localhost:3000/admin/cats)

As you may have expected, this seems like a lot of work for something that’s used quite often. Rails actually makes this even easier for us.

Namespace

namespace = scope + module + as

Rad!

Update the routes file to the following:

	get '/cats', to: 'cats#index'
    	get '/cats/:id', to: 'cats#show'
	namespace :admin do
	 patch '/cats', to: 'cats#update'
   	 get '/cats/edit', to: 'cats#edit'
    	 delete '/cats/:id', to: 'cats#destroy'
	end

vs

        get '/cats', to: 'cats#index'
    	get '/cats/:id', to: 'cats#show'
	scope :admin, module: :admin, as: :admin do
	 patch '/cats', to: 'cats#update'
   	 get '/cats/edit', to: 'cats#edit'
    	 delete '/cats/:id', to: 'cats#destroy'
	end

Why should we use namespace, scope, module, or as?

• readability
• organization
• specificity

Can you imagine what happens when you have 400 lines in your routes file?! You’ll be thankful these route blocks exist for organization alone.

Test Your Understanding

By the end of this work period have a written response to each of the following questions.

• Describe what each of the following things does in the context of our routes file:
  • scope
  • module
  • as
  • namespace
• Why might it be beneficial to have two controllers for Songs (one in controllers/admin and one just in controllers)? Would it have any downsides?
• What about different routes? Would we ever want to have /admin/songs and /songs? Why or why not?