Ryan Bigg

A while after completing work at SeaLink, Tom asked me about my forum hobby project and why it wasn’t working. This led to me working on it for a few days and getting it all up to scratch again, and this involved moving it over to Rails 2.0 (that’s how long I hadn’t worked on it for), and using the awesomeness that is namespacing.

Namespacing is where you have some controllers in a separate area of your site. In my example, I have an admin folder in app/controllers which contains all the controllers for the administration section of my site, and all the relevant actions. Just inside the app/controllers directory, I have the other controllers which do all the basic stuff such as showing forums, basically anything a standard user can do.

It seems to be a fairly common question asked in places, so I figured if I sat down and wrote this, I would have something to send to people, much like my Restful Routes tutorial, which ideally should’ve covered namespacing too.

First of all we’re going to create our namespace. To do that, we open up config/routes.rb and specify our namespace:

map.namespace(:admin) do |admin|
admin.resources :forums, :topics, :posts
end

Now what this does is defines some routes for us. If you’ve seen map.resources you’ll know that this defines routes for us, for example doing map.resources :forums will define methods such as forums_path which is the same as { :controller => “forums”, :action => “index” } and forum_path(@forum) which is the same as { :controller => “forums”, :action => “show”, :id => @forum.id }. These methods really are lifesavers and save you a hell of a lot of typing. The routes defined by this namespace method however are prefixed with whatever argument you pass it, in this case we’ve passed it :admin so it’s going to give us routes like admin_forums_path, which is the same as { :controller = > “admin/forums”, :action => “index” }, and as you can see again saves us a lot of typing.

Now that we have our namespace, we can create our subfolders. These subfolders are placed in app/controllers and app/views and are given the same name as the namespace, admin. So go ahead and do that now. In app/controllers/admin is where we place our controllers. As an example, here’s what my forums controller’s edit and update actions look like:

class Admin::ForumsController < Admin::ApplicationController
  before_filter :store_location, :only => [:index, :show]
  def edit
    @forum = Forum.find(params[:id]) 
    @forums = Forum.find(:all, :order => "title") - [@forum] - @forum.descendants
  end

  def update 
    @forum = Forum.find(params[:id])
    if @forum.update_attributes(params[:forum])
      flash[:notice] = "Forum has been updated."
      redirect
    else
      flash[:notice] = "Forum has not been updated."
      render :action => "edit"
    end
  end
end

What I really want to show you in here is only the first line the class is defined as Admin::ForumsController, which shows that we’re namespacing it. We don’t have to define the Admin prefix anywhere. What we do have to define however is our non-existant Admin::ApplicationController. In my code, I’ve defined my own Admin::ApplicationController as a means of calling methods that should be called before all admin actions, such as my non_admin_redirect method, which is defined in lib/authenticated_system.rb and goes something like this:

  def non_admin_redirect
    if !is_admin?
      flash[:notice] = "You need to be an admin to do that."
      redirect_back_or_default(:controller => "/accounts", :action => "login")
    end
  end

To define your Admin::ApplicationController, make a file in app/controllers/admin called application_controller.rb. Even though the main application controller is defined as application.rb in app/controllers, that file is automatically loaded by Rails. If we named our application_controller to just application.rb, it would not be automatically loaded because Rails only looks for application.rb and files ending in _controller.rb in the app/controllers directory, so we name ours application_controller.rb so it plays nice with Rails.

In here we define our class, layout and helper:

class Admin::ApplicationController < ApplicationController
  layout "admin"
  helper "admin"
  before_filter :non_admin_redirect
end

I’ve defined a new layout here because my admin layout is different to my main layout, but still includes some elements from it (thanks to nested_layouts)

The before_filter is triggered before every action in the admin controller to make sure it’s an admin doing the action rather than a standard user.

And that’s all there is to it, really. It’s all pretty simple. Now all you’ve gotta do is generate your views. Remember to place them in app/views/admin/the_controller’s_name, otherwise you’ll run into problems.

It seems I forgot to mention how it’s supposed to work when you’re calling the method to go to the namespaced path, well that’s simple. If you have a forum you would like to edit, the correct method is edit_admin_forum_path(forum_object), because you want to edit, in the namespace of admin, a certain forum. For paths not requiring a prefix, such as the show and index actions, they are admin_forum_path(forum_object) and admin_forums_path respectively.

For an action such as an update action, it would be admin_forum_path(forum_object) with a :method => :put option specified in whatever you’re using. Usually you won’t have to do this, because the form_for helper would do it for you, but in some cases you might have to.