use .nil? instead of == or != symbol

venshop_app/app/controllers/cards_controller.rb

@@ -3,12 +3,12 @@ class CardsController < ApplicationController
 
   def index
     @card_infos = Hash.new
-    if session[:SHOPPING_CARD_SESSION_NAME] != nil
+    if !session[:SHOPPING_CARD_SESSION_NAME].nil?
       @card_infos = session[:SHOPPING_CARD_SESSION_NAME]
     end
-    if params[:product_id] != nil
+    if !params[:product_id].nil?
       # if remove a product from card
-      if params[:card_action] != nil && params[:card_action] == 'remove'
+      if !params[:card_action].nil? && params[:card_action] == 'remove'
         # Nothing to delete
         if @card_infos.empty?
           redirect_to cards_path
@@ -24,14 +24,14 @@ class CardsController < ApplicationController
             end
           end
         end
-      elsif  params[:card_action] != nil && params[:card_action] == 'update'
+      elsif !params[:card_action].nil? && params[:card_action] == 'update'
          # Nothing to update
         if @card_infos.empty?
           redirect_to cards_path
         else
           quantity = params[:quantity]
           # Invalid request
-          if quantity == nil || quantity.to_i <= 0
+          if quantity.nil? || quantity.to_i <= 0
             redirect_to cards_path
           else
             card_items = @card_infos[:card_items]
@@ -84,7 +84,7 @@ class CardsController < ApplicationController
   def checkout
     add_breadcrumb "Checkout", url_for(action: 'checkout')
     @card_infos = Hash.new
-    if session[:SHOPPING_CARD_SESSION_NAME] != nil
+    if !session[:SHOPPING_CARD_SESSION_NAME].nil?
       @card_infos = session[:SHOPPING_CARD_SESSION_NAME]
     end
     if @card_infos.empty?
@@ -133,7 +133,7 @@ class CardsController < ApplicationController
     add_breadcrumb "Check out", url_for(action: 'checkout')
     add_breadcrumb "Confirm", url_for(action: 'confirm_checkout')
     @card_infos = Hash.new
-    if session[:SHOPPING_CARD_SESSION_NAME] != nil
+    if !session[:SHOPPING_CARD_SESSION_NAME].nil?
       @card_infos = session[:SHOPPING_CARD_SESSION_NAME]
     end
     if @card_infos.empty?

venshop_app/app/controllers/product_categories_controller.rb

@@ -3,7 +3,7 @@ class ProductCategoriesController < ApplicationController
 
   def show
   	term = ProductCategory.find(params[:id])
-  	if term == nil
+  	if term.nil?
   		@items = Array.new
   		@title = ''
   	else

venshop_app/app/controllers/products_controller.rb

@@ -10,12 +10,12 @@ class ProductsController < ApplicationController
     @product = Product.find(params[:id])
     if !@product.status
       user = current_user
-      if user == nil || @product.user_id != user.id
+      if user.nil? || @product.user_id != user.id
         redirect_to products_path
       end
     end
     product_category = ProductCategory.find(@product.product_category_id)
-  	if product_category != nil
+    if !product_category.nil?
       add_breadcrumb product_category.name, product_category_path(product_category)
       add_breadcrumb @product.name, product_path(@product)
     end
@@ -44,13 +44,13 @@ class ProductsController < ApplicationController
   def user_items
     add_breadcrumb "My items", url_for(action: 'user_items')
     user = current_user
-    all_status = user != nil && user.id.to_s == params[:user_id].to_s
+    all_status = !user.nil? && user.id.to_s == params[:user_id].to_s
     @products = Product.get_user_items(limit: 16, page: params[:page], user_id: params[:user_id], all_status: all_status)
   end
 
   def search
     add_breadcrumb "Search results", url_for(action: 'search')
-    if params[:keyword] == nil
+    if params[:keyword].nil?
       redirect_to products_path
     end
     search = Product.search do

venshop_app/app/views/layouts/_breadcrumb.html.erb

@@ -2,7 +2,7 @@
           <span>You are in: </span>
           <ul>
             <%
-            if breadcrumbs == nil || breadcrumbs.empty?
+            if breadcrumbs.nil? || breadcrumbs.empty?
             	breadcrumbs = Array.new
             	breadcrumbs.push({ text: 'Home', url: root_path })
             else

venshop_app/app/views/shared/_grid.html.erb

           <%
-          if items == nil || items.empty?
+          if items.nil? || items.empty?
             if params[:action] != 'search'
           %>
             <p>No products available.</p>

[Vinh Nguyen]

• use unless
• use blank? instead of nil?