Namespaced Routes

Objectives

Understand the use of scope and namespace in routes.rb.
Create a module scoped controller.

Lesson

We're going to explore different ways of routing things in our blog application to help us organize and group certain routes, and controllers, more logically.

Blog Stats

We decide that we want to keep track of some basic blog statistics, things like how many posts and authors we have. We start by creating a stats_controller.rb with an index action, and a corresponding view.

We can't actually browse to it yet, so we need to set up a route. Let's add it to routes.rb:

# config\routes.rb

# ...
get '/stats', to: 'stats#index'

Easy enough, but after thinking about it, /stats isn't something we want to just hang off the root of our blog URL for anyone to see. It's really just for blog admins, and we want to set up a URL scheme to segregate admin things into their own logical space.

We modify our route:

# config\routes.rb

# ...
get '/admin/stats', to: 'stats#index'

Now we can browse to /admin/stats for the stats page, and we can no longer go straight to /stats.

Scoping Routes

Over time, we might decide to add more admin functions, grouping them all together like we did above, until eventually our routes.rb looks something like this:

# config\routes.rb

# ...
get '/admin/stats', to: 'stats#index'
get '/admin/authors/new', to: 'authors#new'
get '/admin/authors/delete', to: 'authors#delete'
get '/admin/authors/create', to: 'authors#create'
get '/admin/comments/moderate', to: 'comments#moderate'

As you can see, even with only a few more actions in our admin section, our routes are getting ugly. Not to mention we're repeating ourselves a lot by typing in /admin/ on all these routes. Yes, even routes should be DRY!

What we need is a way to group all these under /admin without typing /admin all the time. That's where scope comes in.

In routing, scope allows us to prefix a block of routes under one grouping. So let's change our stats route:

# config\routes.rb

# ...
scope '/admin' do
  resources :stats, only: [:index]
end

Now we reload /admin/stats and it still works. Notice our new route is resourced. Now that we don't have to manually prefix /admin we can go back using resourced routes under this scope.

If you run rake routes, you'll see that the new /admin/stats helpers are stats_path and stats_url.

Scoping With Modules

Scoping works nicely to group our URLs together logically, but what happens when we have a bunch of controllers that are handling admin functions? As the application grows, it's going to be harder and harder to keep track of which controllers are for regular blog functions and which are for admin functions.

We want to group all our admin controllers logically to make it easier to maintain and add to the app, so let's add a /admin directory under /controllers where all the admin controllers will go:

mkdir app/controllers/admin

Now let's move our stats_controller.rb into the /admin folder.

When you create a new folder under /controllers, Rails will automatically pick that up as a module, and expect you to namespace the controller accordingly, so we need to modify our admin/stats_controller.rb to look like this:

# controllers/admin/stats_controller.rb

class Admin::StatsController < ApplicationController
  def index
     # ...
  end
end

Now that we have our controller in a module, Rails will expect the views to match, so let's create /app/views/admin/stats/ and move our stats/index.html.erb into it, so that we have an /app/views/admin/stats/index.html.erb.

Top-tip: The views folder for a controller module, in this case /admin, still expects a subfolder structure that matches the names of the controllers, so in this case, /admin/stats.

If we try to reload /admin/stats now, we will get an error, because we need to tell our routes about our new module.

# routes.rb

  scope '/admin', module: 'admin' do
    resources :stats, only: [:index]
  end

We're telling scope that we want to use /admin as a URL prefix, and that all of the included routes will be handled by controllers in the admin module.

If we reload /admin/stats, everything should work just like it did, but now we are logically organizing our controllers.

Namespace

Right now, our route is scoped like this: scope '/admin', module: 'admin', which is fine, but maybe a little less DRY than we'd like.

Fortunately, Rails gives us a shortcut here so that when we want to route with a module and use that module name as the URL prefix, we can use the namespace method instead of scope, module.

# routes.rb

  namespace :admin do
    resources :stats, only: [:index]
  end

If we reload /admin/stats, everything still works, but we've simplified the declaration of the routes. The namespace method makes the assumption that the prefix and the module should match, saving us some typing.

Top-tip: There is one important difference between scope '/admin', module: 'admin' and namespace :admin, and it's in the URL helpers. Remember above that using scope gave us a stats_path helper. But now that we are using namespace, run rake routes again. You'll see that the helper is now prefixed with admin_, so stats_path becomes admin_stats_path. So if you switch from scope to namespace, take care to update any URL helpers you have in use!

Summary

We learned how to organize our URLs by using scope to group them with an /admin prefix, and to further organize our controllers using directories and modules and scope module or namespace in our routes.

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