fix errors

app/controllers/jobs_controller.rb

 class JobsController < ApplicationController
   before_action :set_job, only: [:show]
   def index
-    @jobs = Job.preload(:company).order(updated_date: :desc).limit(5)
+    @jobs = Job.includes(:company).order(updated_date: :desc).limit(5)
     @cities = City.top_cities
     @industries = Industry.top_industries
   end
@@ -13,21 +13,21 @@ class JobsController < ApplicationController
     city = City.find(params[:city_id])
     @jobs = city.jobs.includes(:company).page(params[:page]).per(20)
     @result = "jobs/City/#{city.name}"
-    render :action => :job_lists
+    render template: "jobs/job_lists"
   end
 
   def industry
     industry = Industry.find(params[:industry_id])
     @jobs = industry.jobs.includes(:company).page(params[:page]).per(20)
     @result = "jobs/Industry/#{industry.name}"
-    render :template => "jobs/job_lists"
+    render template: "jobs/job_lists"
   end
 
   def company
     company = Company.find(params[:company_id])
     @jobs = company.jobs.page(params[:page]).per(20)
     @result = "jobs/Company/#{company.name}"
-    render :template => "jobs/job_lists"
+    render template: "jobs/job_lists"
   end
 
   def set_job

app/models/city.rb

@@ -4,14 +4,13 @@ class City < ApplicationRecord
   has_many :cities_jobs
   has_many :jobs, through: :cities_jobs
 
-  scope :top_cities, -> { select('id, name, jobs_count').
-                          where('jobs_count > 0').
+  scope :top_cities, -> { have_at_least_one_job.
                           order(jobs_count: :desc).
                           limit(9) }
 
-  scope :city_list, -> { select('cities.id, cities.name AS name, countries.name AS country_name, cities.jobs_count').
-                         joins(:country).
-                         where('jobs_count > 0').
-                         order('jobs_count DESC, name') }
+  scope :city_list, -> { includes(:country).
+                         have_at_least_one_job.
+                         order(jobs_count: :desc, name: :asc) }
 
+  scope :have_at_least_one_job, -> { where('jobs_count > 0')}
 end

app/models/industry.rb

 class Industry < ApplicationRecord
-  # has_and_belongs_to_many :jobs
   has_many :industries_jobs
   has_many :jobs, through: :industries_jobs
 
-  scope :top_industries, -> { select('id, name, jobs_count').
-                              where('jobs_count > 0').
-                              order('jobs_count DESC, name').
+  scope :top_industries, -> { have_at_least_one_job.
+                              order(jobs_count: :desc, name: :asc).
                               limit(9) }
 
-  scope :industry_list, -> { select('id, name, jobs_count').
-                             where('jobs_count > 0').
-                             order('jobs_count DESC, name') }
+  scope :industry_list, -> { have_at_least_one_job.
+                             order(jobs_count: :desc) }
+
+  scope :have_at_least_one_job, -> { where('jobs_count > 0')}
 end

app/views/cities/_city.html.erb

 <div class="col-md-<%= column %>">
   <div class="job-intro well mr0 mrBot20" id="vietnam">
-    <h4 class="mr0"><%= link_to city.name, _city_jobs_path(city) %></h4>
+    <h4 class="mr0"><%= link_to city.name, city_jobs_path(city) %></h4>
     <p>Jobs: <span class="badge"><%= city.jobs_count %></span></p>
   </div>
 </div>

app/views/cities/index.html.erb

@@ -10,10 +10,10 @@
       <div id="vietnam" class="city">
         <p><h4>Viet Nam</h4></p>
         <%- @cities.each do |city| -%>
-          <%- if city.country_name.eql?(Country::VIETNAM) -%>
+          <%- if city.country.name.eql?(Country::VIETNAM) -%>
           <div class="col-md-3 maxH109">
             <div class="job-intro well mr0 mrBot20 maxH89">
-              <h4 class="mr0"><%= link_to city.name, _city_jobs_path(city) %></h4>
+              <h4 class="mr0"><%= link_to city.name, city_jobs_path(city) %></h4>
               <p>Jobs: <span class="badge"><%= city.jobs_count %></span></p>
             </div>
           </div>
@@ -24,10 +24,10 @@
       <div id="international" class="city">
         <p><h4>International</h4></p>
         <%- @cities.each do |city| -%>
-          <%- if city.country_name.eql?(Country::ANOTHER) -%>
+          <%- if city.country.name.eql?(Country::ANOTHER) -%>
           <div class="col-md-3 maxH109">
             <div class="job-intro well mr0 mrBot20 maxH89">
-              <h4 class="mr0"><%= link_to city.name, "#{jobs_path}/city/#{city.id}" %></h4>
+              <h4 class="mr0"><%= link_to city.name, city_jobs_path(city) %></h4>
               <p>Jobs: <span class="badge"><%= city.jobs_count %></span></p>
             </div>
           </div>

app/views/industries/_industry.html.erb

 <div class="col-md-<%= column %> maxH109">
   <div class="job-intro well mr0 mrBot20 maxH89">
-    <h4 class="mr0"><%= link_to industry.name, _industry_jobs_path(industry) %></h4>
+    <h4 class="mr0"><%= link_to industry.name, industry_jobs_path(industry) %></h4>
     <p>Jobs: <span class="badge"><%= industry.jobs_count %></span></p>
   </div>
 </div>

app/views/jobs/show.html.erb

@@ -5,13 +5,13 @@
       <li>
         <%- @job.cities.each_with_index do |city, index| -%>
           <%= "#{index > 0 ? ',' : ''}" %>
-        <%= link_to city.name, _city_jobs_path(city) %>
+          <%= link_to city.name, city_jobs_path(city) %>
         <%- end -%>
       </li>
       <li>
         <%- @job.industries.each_with_index do |industry, index| -%>
           <%= "#{index > 0 ? ',' : ''}" %>
-        <%= link_to industry.name, _industry_jobs_path(industry) %>
+          <%= link_to industry.name, industry_jobs_path(industry) %>
         <%- end -%>
       </li>
       <li><%= @job.name %></li>
@@ -20,11 +20,11 @@
   <div class="job">
     <div class="col-md-9">
       <h1>2.<%= @job.name %></h1>
-      <p>3.<%= link_to @job.company.name, _company_jobs_path(@job.company) %></p>
+      <p>3.<%= link_to @job.company.name, company_jobs_path(@job.company) %></p>
       <p>4. Location:
         <%- @job.cities.each_with_index do |city, index| -%>
           <%= "#{index > 0 ? ',' : ''}" %>
-        <%= link_to city.name, _city_jobs_path(city) %>
+          <%= link_to city.name, city_jobs_path(city) %>
         <%- end -%>
       </p>
       <p>5. Salary: <%= @job.salary %></p>

config/routes.rb

 Rails.application.routes.draw do
+  root 'jobs#index'
   devise_for :users
-  get 'jobs/index'
-  resources :cities, :industries, :jobs do
-    get 'cities' => 'cities#index'
-    get 'industries' => "industries#index"
+
+  resources :cities, only: [:index, :show]
+  resources :industries, only: [:index, :show]
+  resources :jobs do
     collection do
-      get 'city/:city_id' => "jobs#city", as: :_city
-      get 'industry/:industry_id' => "jobs#industry", as: :_industry
-      get 'company/:company_id' => "jobs#company", as: :_company
+      get 'city/:city_id' => "jobs#city", as: :city
+      get 'industry/:industry_id' => "jobs#industry", as: :industry
+      get 'company/:company_id' => "jobs#company", as: :company
     end
   end
-  root 'jobs#index'
 end

db/migrate/20171016091751_add_index_to_cities.rb

+class AddIndexToCities < ActiveRecord::Migration[5.1]
+  def change
+    add_index :cities, :jobs_count
+  end
+end

db/migrate/20171016091830_add_index_to_industries.rb

+class AddIndexToIndustries < ActiveRecord::Migration[5.1]
+  def change
+    add_index :industries, :jobs_count
+  end
+end

db/schema.rb

@@ -10,7 +10,7 @@
 #
 # It's strongly recommended that you check this file into your version control system.
 
-ActiveRecord::Schema.define(version: 20171016030017) do
+ActiveRecord::Schema.define(version: 20171016091830) do
 
   create_table "apply_jobs", force: :cascade, options: "ENGINE=InnoDB DEFAULT CHARSET=utf8" do |t|
     t.bigint "job_id"
@@ -29,6 +29,7 @@ ActiveRecord::Schema.define(version: 20171016030017) do
     t.datetime "updated_at", null: false
     t.integer "jobs_count", default: 0
     t.index ["country_id"], name: "index_cities_on_country_id"
+    t.index ["jobs_count"], name: "index_cities_on_jobs_count"
   end
 
   create_table "cities_companies", id: false, force: :cascade, options: "ENGINE=InnoDB DEFAULT CHARSET=utf8" do |t|
@@ -73,6 +74,7 @@ ActiveRecord::Schema.define(version: 20171016030017) do
     t.datetime "created_at", null: false
     t.datetime "updated_at", null: false
     t.integer "jobs_count", default: 0
+    t.index ["jobs_count"], name: "index_industries_on_jobs_count"
   end
 
   create_table "industries_jobs", force: :cascade, options: "ENGINE=InnoDB DEFAULT CHARSET=utf8" do |t|