JasonDaly.name

Decorating Models from the View Layer with Draper

Draper is a great gem allowing for the Decorator pattern to easily be applied to ActiveRecord models.

When integrating Draper into an existing application, a decorator or collection of decorators must be retrieved/built instead of ActiveRecord models in order to use the functionality of your decorators (the decorators include all functionality of the ActiveRecord model they’re decorating). Draper’s README explains three methods for doing this from within the controller:

• Call .new and pass in the object to be wrapped

  ArticleDecorator.new(Article.find(params[:id]))
  

• Call .decorate and pass in an object or collection of objects to be wrapped:

  ArticleDecorator.decorate(Article.first) # Returns one instance of ArticleDecorator
  ArticleDecorator.decorate(Article.all)   # Returns an array of ArticleDecorator instances
  

• Call .find to do automatically do a lookup on the decorates class:

  ArticleDecorator.find(1)
  

I’d like to decorate ActiveRecord models from the view directly, leaving the controllers unchanged (directly fetching the record(s) through ActiveRecord). I use the following decorate method in app/helpers/application_helper.rb.

def decorate(records)
  collection = [records] if !objects.is_a? Array
  return records unless collection.first.class.name.match(/Decorator$/).nil?
  klass = (collection.first.class.name + 'Decorator').constantize

  decorated_objects = []
  collection.each do |object|
    decorated_records.push(klass.decorate(object))
  end

  return decorated_records if records.is_a? Array
  decorated_records.first
end

Now I can simply wrap any record or collection with decorate in any view to leverage the decorator functionality.

Using intern to Reference Routes Dynamically

In config/routes.rb if routes such as the following exist:

match "users/customers" => "users#customers", :as => :users_customers, :via => :get
match "users/employees" => "users#employees", :as => :users_employees, :via => :get 

match "users/:id/toggle-status" => "users#toggle_status", :as => :users_toggle_status, :via => :put

the views associated with the :users_customers and :users_employees actions above (in this case each displaying a list-view of users of the specified type) likely both have a link referencing the :users_toggle_status route.

Within the toggle_status action the route to redirect back to can be determined by looking at the type of user who’s status is being toggled. A sample version of this action is below.

def toggle_status
    user = User.find(params[:id])
    user.toggle_status!

    if user.type == 'employee'
      redirect_to :users_employees and return
    end

    redirect_to :users_customers and return
end

The condition above and multiple redirect_to’s is cumbersome and unnecessary. Instead, we can use Ruby’s intern method for strings.

def toggle_status
    user = User.find(params[:id])
    user.toggle_status!

    redirect_to ('users_%s' % user.type).intern and return
end

Reverse Pagination Count with Kaminari

When displaying a threaded conversation with messages paginated by Kaminari, I had the unique requirement to display messages in DESC order by their creation date. This meant that if there were 12 messages with 5 per page, the breakdown would be

• Page 1: messages 12 - 8
• Page 2: messages 7 - 3
• Page 3: messages 2 - 1

To actually display the message number next to each message, it had to be calculated using the methods added to a paginated model by Kaminari (see the :message_number value below)

<div class="comments">
  <% @messages.each_with_index do |message, index| %>
    <%= render :partial => 'message', :locals => {:message => message, :message_number => @messages.total_count - (@messages.current_page - 1) * @messages.limit_value - index} %>
  <% end %>
</div>

For now this is the only place the above calculation is relevant. Should I need it in multiple places I would move the above calculation to a helper.

Parsing and Pluralizing Model Names in Rails

Recently working with Kaminari, I wanted to have text display next to the pagination links like

283 Items - Page 3/15

I wanted the Items text to be dynamic according to the model the paginated collection was representing. Looking over my model names I found converting each to a human readable version would work great in all cases I needed a paginator. Simply using pluralize (I use singular form for my models) will not work in all cases.

• User would become Users - great!
• Page would become Pages - great!
• ConversationMessage would become ConversationMessages - yuck!

For the ConversationMessage model, I really only wanted to display the items in the collection to the user as Messages, not ConversationMessages or even Conversation Messages. I found this was common for my other models on the many side of a one-to-many relationship too (ie. for my UserComplaint model, I wanted the pagination text to say simply Complaints).

The following works beautifully for all models I currently have in place

@collection.first.class.name.underscore.humanize.pluralize.titleize[/\s?([^\s]+)$/, 1]

With models having their default names (in the plural form), the .pluralize call can be removed.