The Contacts Module: Extending Models & Controllers

Step 1: The Decorator folder

To keep it organized, we’ll extend models and controllers in files called decorators.

By using the modular_engine generator, you should have a decorators/ folder in your engine’s app/ folder. In there, you will find two more folders: models/ and controllers/. We’re going to create one decorator for each class that we want to extend. But first, let’s make sure our decorators will be loaded by Rails automatically.

Step 2: Load the decorators

To load the content of your decorators, we need to tell Rails to load them. Actually, with the gem we used to generate the engine, the piece of code to do it should already be there, but let’s take a look.

Open the engine.rb file in the Contacts engine (located in lib/blast/contacts). You should see the contents of Listing 1 somewhere inside the engine file:

# ...
  config.to_prepare do
    Dir.glob(Engine.root.join("app", "decorators", "**", "*_decorator*.rb")) do |c|
      Rails.configuration.cache_classes ? require(c) : load(c)
    end
  end
# ...

And that’s all the magic we need to load our decorators!

Step 3: Create a decorator for the User model

Now, let’s try it. Create a decorator for User from the Contacts engine folder, and put the code from Listing 2 inside:

touch app/decorators/models/user_decorator.rb

Blast::User.class_eval do
  has_many :contacts, class_name: "Blast::Contacts::Contact"
end

And that’s it! You can put anything you’d like to add to the User model in the class_eval block. Note however, that we need to provide the namespaced name of the module we’re linking, otherwise it will try to find the Contact model in the Blast::User scope, instead of the Blast::Contacts scope!

Step 4: A quick test in the console

Let’s see if what we just did is working. Fire up the rails console and type Blast::User.first.contacts (Obviously, you need a user, but we have already created some).

You should get a CollectionProxy object showing up in your terminal:

Loading development environment (Rails 5.2.3)
2.6.3 :001 > Blast::User.first.contacts
  ... [output] ...
 => #<ActiveRecord::Associations::CollectionProxy []> 

Step 5: Update the Contacts controller

A few steps back, we added the possibility to show all the contacts to a user. But that’s not the behavior we want. We want to show a user only his contacts.

To do this, we need to change the value we give to @contacts in the index action of the ContactsController, as shown in Listing 3:

# ...
  def index
    @contacts = current_user.contacts
  end
# ...

Thanks to the has_many relationship that we added, it’s working! Time to extend the dashboard!

Step 1: Add a hook

You know the drill already… let’s add a hook to the dashboard view, as shown in Listing 4, so we can easily extend it in the Contacts engine. We’re going to call this hook dashboard.

<h2>Dashboard</h2>
<hr>

<div class="row">

  <!-- The Dashboard Hook -->
  <span data-blast-hook='dashboard'></span>

</div>

A simple span is enough for the dashboard. We’re going to insert code right after it with Deface.

Step 2: Add an override

Time to create a new override that will be responsible for adding a list of contacts on the dashboard:

touch app/overrides/add_contacts_list_to_dashboard.rb

Deface::Override.new(:virtual_path => "blast/dashboard/index",
                     :name => "add_contacts_list_to_dashboard",
                     :insert_after => "[data-blast-hook='dashboard']",
                     :partial => "overrides/contacts_list",
                     :namespaced => true)

Step 3: Add an override view

And finally, the list of contacts. This is a simple view with a table showing a user’s contacts.

touch app/views/blast/contacts/overrides/_contacts_list.html.erb

<div class="col-md-6">
  <div class="panel panel-primary">
    <div class="panel-heading">
      Last 3 Contacts
    </div>
    <table class="table">
      <thead>
        <th>ID</th>
        <th>Name</th>
        <th>Email</th>
        <th>Created On</th>
      </thead>
      <tbody>
        <%- current_user.contacts.each do |contact| %>
          <tr>
            <td><%= contact.id %></td>
            <td><%= contact.first_name %> <%= contact.last_name %></td>
            <td><%= contact.email %></td>
            <td><%= contact.created_at.strftime("%d %b. %Y") %></td>
          </tr>
        <% end %>
      </tbody>
    </table>

    <div class="panel-body text-center">
      <%= link_to '...', contacts_path %>
    </div>
  </div>
</div>

Did you see how we got the list of contacts? We used current_user.contacts directly in the view. That’s not really “good practice” so we’ll move it to the controller in a bit. First, let’s take a look at Figure 1 to see what we’ve accomplished:

Figure 1

Now let’s change how we get the list of contacts!