adds counter cache for user's notifications

app/models/notification.rb

@@ -1,5 +1,5 @@
 class Notification < ActiveRecord::Base
-  belongs_to :user
+  belongs_to :user, counter_cache: true
   belongs_to :notifiable, polymorphic: true
 
   scope :unread, -> { all }

app/views/devise/menu/_login_items.html.erb

@@ -2,9 +2,9 @@
   <% if user_signed_in? %>
     <li>
       <%= link_to notifications_path, class: "notifications" do %>
-        <% if current_user.notifications.count > 0 %>
+        <% if current_user.notifications_count > 0 %>
           <i class="icon-circle"></i>
-          <i class="icon-notification" title="<%= t('layouts.header.new_notifications', count: current_user.notifications.count).html_safe %>">
+          <i class="icon-notification" title="<%= t('layouts.header.new_notifications', count: current_user.notifications_count).html_safe %>">
           </i>
         <% else %>
           <i class="icon-no-notification" title="<%= t('layouts.header.no_notifications') %>"></i>

db/migrate/20160108133501_add_notifications_counter_cache_to_user.rb

@@ -0,0 +1,5 @@
+class AddNotificationsCounterCacheToUser < ActiveRecord::Migration
+  def change
+    add_column :users, :notifications_count, :integer, default: 0
+  end
+end

db/schema.rb

@@ -11,7 +11,7 @@
 #
 # It's strongly recommended that you check this file into your version control system.
 
-ActiveRecord::Schema.define(version: 20160108114750) do
+ActiveRecord::Schema.define(version: 20160108133501) do
 
   # These are extensions that must be enabled in order to support this database
   enable_extension "plpgsql"
@@ -339,6 +339,7 @@ ActiveRecord::Schema.define(version: 20160108114750) do
     t.datetime "erased_at"
     t.boolean  "public_activity",                      default: true
     t.boolean  "newsletter",                           default: false
+    t.integer  "notifications_count",                  default: 0
   end
 
   add_index "users", ["confirmation_token"], name: "index_users_on_confirmation_token", unique: true, using: :btree