Question

How is the best way to load Category model, for ProductController in new, edit update and create actions

Product has categories collection

class Product < ActiveRecord::Base
  has_many :categories
end 

Always for new, edit, create and update actions, I need to load the categories collection to populate a check_box_tag list

The “baby steps” for this situation is:

class Admin::ProductsController < Admin::AdminApplicationController

 def new
   @product = Product.new
   @categories = Category.all
 end

 def edit
   @product = Product.find(params[:id])
   @categories = Category.all
 end

 def create
   @product = Product.new(params[:product])
   if @product.save
     flash[:notice] = 'Product was successfully created'
     redirect_to edit_admin_product_path(@product)
   else
     @categories = Category.all
     render :new
  end
 end

 def update
   @product = Product.find(params[:id])
   @product.update_attributes(params[:product])
   if @product.save
     flash[:notice] = 'Product was successfully updated'
     redirect_to edit_admin_product_path(@product)
   else
     @categories = Category.all
     render :edit
   end
 end
end 

I don’t want to load always Category.all in different situations for same purpose

Options:

First – load categories over the view:

<% Category.all.each do |cat| %>
  <li>
    <%= check_box_tag .... %>
  </li>
<% end %>

:/

Second – load categories over the ProductsHelper :

module ProductsHelper

  def categories
   Category.all
  end

end

:/

“Third” – Exist a filter like ‘before_render’?

class Admin::ProductsController < Admin::AdminApplicationController

  before_render :load_categories :edit, :new

  def load_categories
    @categories = Category.all
  end

end

😀 😀 😀

What’s the rails way for this situations?

Best Regards,
Pablo Cantero

Answer 1

In your controller, or if needed elsewhere, in application_controller.rb:

def all_categories
  @all_categories ||= Category.all
end
helper_method :all_categories

The first time it’s called, it will hit the db, and later it will return the controller instance variable.