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Adding an Administration subsite to an existing Rails 3 application

This tutorial will show how you can create an administrative subsite for an existing Rails application. This will allow the administrator to create, update and destroy any database row without writing any view code -- only three lines of controller code for each model!

It should also be useful for those who wish to add a subsite to a Hobo application. If you already have a Hobo application, some of the steps mentioned here will be unnecessary.

In this tutorial, we've placed the Hobofied controllers and views in a subsite. However, it is certainly possible to mix Hobo code into your existing controllers. If you have any questions, the mailing list is probably your best resource.

Install Hobo

The application that I'm going to convert is called scheduler. Let's add a Hobo dependency to it.

$ gem install hobo

Inside the Gemfile add:

gem 'hobo'

It might be a good idea to run your application and confirm that everything still works.

Now might also be a good time to make sure you have your source code backed up, preferably in an SCM tool like git or subversion. We're going to be running some generators: they will ask you before eventually overwriting some existing file, but just in case you make any mistake.

Notice: When you run in a conflict with an existing file you can see the diffs by typing 'd'. Check also the other options.

Run the Hobo generators

Now we'll ask Hobo to copy it's shared files into your application. These are mostly javascript, css and dryml files

$ hobo g assets
$ hobo g rapid

Now let's create our admin subsite:

$ hobo g subsite admin --make-front-site
$ hobo g front_controller admin::front --add-routes

Note that if you use admin_subsite rather than subsite, the subsite will be limited to the administrator. For this to work, you will need to complete the section labelled "Updating your User Model", below.

Hobofying a model

Adding the Hobo magic to a model requires two things:

Add this to the top of your model:

Class Event < ActiveRecord::Base
  hobo_model # Don't put anything above this

Secondly, all Hobo models require four permission functions. Here is what I use in my user model:

# --- Permissions --- #

def create_permitted?

def update_permitted?
  acting_user.administrator? || (acting_user == self && only_changed?(:crypted_password, :email_address))
  # Note: crypted_password has attr_protected so although it is permitted to change, it cannot be changed
  # directly from a form submission.

def destroy_permitted?

def view_permitted?(field)

For now, I recommend returning true from all of these permission functions. After hobofying your User model, these functions will become easier to write.

If your model does not have a column called "name", I recommend defining a function on your model that returns a human readable summary of the row.

Creating a controller for the hobofied model:

I'm going to create an Admin::Event controller for my event model. This file goes in app/controllers/admin/events_controller.rb:

class Admin::EventsController < Admin::AdminSiteController
  hobo_model_controller Event
  auto_actions :all

At this stage you should be able to run your application. If you browse to "/admin/events", you can create, remove, update and destroy any events you have permission to access.

Modifying the views

If you need to modify the views for your subsite, you may create subdirectories in app/views/admin. For example, app/views/admin/foos/show.dryml is the show view for the foos controller.

app/views/taglibs/admin_site.dryml is the equivalent of application.dryml for your subsite.

Updating your User model

At this stage you have created an administrator interface, and could stop here. However, as far as Hobo is concerned, any users are logged in as a guest. To distinguish administrators from normal users from random surfers, hackers and bots, we will need to set up an authentication system.

If you don't have one

If you don't currently have a User model, type:

$ hobo g user_resource User
$ hobo g migration

The last generator will ask if you wish to run the migration immediately. Enter "m" to tell it to do so.

The following pages will now be available:

  • /users/signup
  • /forgot_password
  • /login
  • /logout

If you have a User model

Most likely, you already have a User model and authentication system. In most cases, it is quite easy to make this Hobo compatible.

First of all, you should add the following line to the top of your model:

hobo_model # Don't put anything above this

Do not use hobo_user_model -- this will pull in authentication functions and database columns.

Many User models have the columns name:string and administrator:boolean. If your model does not, create appropriate functions to mimic this behaviour. For example:

def name
  "#{first_name} #{last_name}"

def administrator
  role == "administrator"

Also, Hobo requires the following functions to be defined on your User model. Define appropriately. Here is what I used:

def to_s

def guest?

def signed_up?

def login

Finally, you need to let Hobo know who the current user is. This is done by setting a session variable when the user logs in:

session[:user] = user.typed_id

In my case, a very similar line was placed in SessionsController::create

From now on, an instantiated User or Guest object will be available in current_user in your controllers and views. It will also be available in acting_user in your permission functions in your hobofied models.

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