Advanced Routing in Rails

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?
• In what case should you use Nested Resources?

Warm Up

How confident are you that you can create all 8 prefixes, http-verbs, URI-patterns, and controller actions that Rails gives you when you have the following?

# config/routes.rb

resources :cats

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

Resource Routes Recap:

Let’s add some resource routes to our routes.rb for cats.

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
	scope :admin do
	 resources :cats
	end

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

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

	scope :admin, module: :admin do
	 resources :cats
	end

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

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

	scope :admin, module: :admin, as: :admin do
	 resources :cats
	end

Let’s run rake routes once again!

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!

	namespace :admin do
	 resources :cats
	end

vs

	scope :admin, module: :admin, as: :admin do
	 resources :cats
	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.

Nested Resources

Imagine we have these relationships:

	class Owner < ActiveRecord::Base
	 has_many :cats
	end

	class Cat < ActiveRecord::Base
	 belongs_to :owner
	end

Let’s set up our resource routes as follows:

resources :owners do
 resources :cats
end

Run rake routes now. Why might we want this setup for our routes?

Recap

Turn and talk to your neighbor and discuss:

• What are differences between using namespace and nested resources?
• What are use cases for one or the other? Could you think of use cases for both?

Closing

Can you answer these questions?

• Why do we namespace things?
• What is the difference between namespacing and scoping?
• When would we use one over the other?
• When should you use nested resources?