Agile Web Development with Rails, Edition 4

10.4 Playtime 10.2 Iteration E2: Handling Errors

10.3 Iteration E3: Finishing the Cart

Add empty cart button, remove flash for line item create, add totals to view.

Add button to the view.

edit app/views/carts/show.html.erb
<p id="notice"><%= notice %></p>
 
<h2>Your Pragmatic Cart</h2>
<ul>    
  <% @cart.line_items.each do |item| %>
    <li><%= item.quantity %> &times; <%= item.product.title %></li>
  <% end %>
</ul>
 
<%= button_to 'Empty cart', @cart, method: :delete,
    data: { confirm: 'Are you sure?' } %>

Clear session and change flash notice when cart is destroyed.

edit app/controllers/carts_controller.rb
  def destroy
    @cart.destroy if @cart.id == session[:cart_id]
    session[:cart_id] = nil
    respond_to do |format|
      format.html { redirect_to store_index_url,
        notice: 'Your cart is currently empty' }
      format.json { head :no_content }
    end
  end

Try it out.

get /carts/1

Your Pragmatic Cart

  • 3 × Seven Mobile Apps in Seven Weeks
  • 1 × Rails, Angular, Postgres, and Bootstrap
post /carts/1
You are being redirected. 
get http://localhost:3000/store/index

Your cart is currently empty

Your Pragmatic Catalog

Dcbang

Rails, Angular, Postgres, and Bootstrap

Powerful, Effective, and Efficient Full-Stack Web Development As a Rails developer, you care about user experience and performance, but you also want simple and maintainable code. Achieve all that by embracing the full stack of web development, from styling with Bootstrap, building an interactive user interface with AngularJS, to storing data quickly and reliably in PostgreSQL. Take a holistic view of full-stack development to create usable, high-performing applications, and learn to use these technologies effectively in a Ruby on Rails environment.

$45.00
Adrpo

Ruby Performance Optimization

Why Ruby Is Slow, and How to Fix It You don’t have to accept slow Ruby or Rails performance. In this comprehensive guide to Ruby optimization, you’ll learn how to write faster Ruby code—but that’s just the beginning. See exactly what makes Ruby and Rails code slow, and how to fix it. Alex Dymo will guide you through perils of memory and CPU optimization, profiling, measuring, performance testing, garbage collection, and tuning. You’ll find that all those “hard” things aren’t so difficult after all, and your code will run orders of magnitude faster.

$46.00
7apps

Seven Mobile Apps in Seven Weeks

Native Apps, Multiple Platforms Answer the question “Can we build this for ALL the devices?” with a resounding YES. This book will help you get there with a real-world introduction to seven platforms, whether you’re new to mobile or an experienced developer needing to expand your options. Plus, you’ll find out which cross-platform solution makes the most sense for your needs.

$26.00

Remove scaffolding generated flash notice for line item create.

edit app/controllers/line_items_controller.rb
  def create
    product = Product.find(params[:product_id])
    @line_item = @cart.add_product(product)
 
    respond_to do |format|
      if @line_item.save
        format.html { redirect_to @line_item.cart }
        format.json { render :show,
          status: :created, location: @line_item }
      else
        format.html { render :new }
        format.json { render json: @line_item.errors,
          status: :unprocessable_entity }
      end
    end
  end

Update the view to add totals.

edit app/views/carts/show.html.erb
<p id="notice"><%= notice %></p>
 
<h2>Your Cart</h2>
<table>
  <% @cart.line_items.each do |item| %>
    <tr>
      <td><%= item.quantity %>&times;</td>
      <td><%= item.product.title %></td>
      <td class="item_price"><%= number_to_currency(item.total_price) %></td>
    </tr>
  <% end %>
 
  <tr class="total_line">
    <td colspan="2">Total</td>
    <td class="total_cell"><%= number_to_currency(@cart.total_price) %></td>
  </tr>
 
</table>
 
<%= button_to 'Empty cart', @cart, method: :delete,
    data: { confirm: 'Are you sure?' } %>

Add a method to compute the total price of a single line item.

edit app/models/line_item.rb
 
  def total_price
    product.price * quantity
  end

Add a method to compute the total price of the items in the cart.

edit app/models/cart.rb
  def total_price
    line_items.to_a.sum { |item| item.total_price }
  end

Add some style.

edit app/assets/stylesheets/carts.css.scss
// Place all the styles related to the Carts controller here.
// They will automatically be included in application.css.
// You can use Sass (SCSS) here: http://sass-lang.com/
 
.carts {
  .item_price, .total_line {
    text-align: right;
  }
 
  .total_line .total_cell {
    font-weight: bold;
    border-top: 1px solid #595;
  }
}

Add a product to the cart, and see the total.

get /

Your Pragmatic Catalog

Dcbang

Rails, Angular, Postgres, and Bootstrap

Powerful, Effective, and Efficient Full-Stack Web Development As a Rails developer, you care about user experience and performance, but you also want simple and maintainable code. Achieve all that by embracing the full stack of web development, from styling with Bootstrap, building an interactive user interface with AngularJS, to storing data quickly and reliably in PostgreSQL. Take a holistic view of full-stack development to create usable, high-performing applications, and learn to use these technologies effectively in a Ruby on Rails environment.

$45.00
Adrpo

Ruby Performance Optimization

Why Ruby Is Slow, and How to Fix It You don’t have to accept slow Ruby or Rails performance. In this comprehensive guide to Ruby optimization, you’ll learn how to write faster Ruby code—but that’s just the beginning. See exactly what makes Ruby and Rails code slow, and how to fix it. Alex Dymo will guide you through perils of memory and CPU optimization, profiling, measuring, performance testing, garbage collection, and tuning. You’ll find that all those “hard” things aren’t so difficult after all, and your code will run orders of magnitude faster.

$46.00
7apps

Seven Mobile Apps in Seven Weeks

Native Apps, Multiple Platforms Answer the question “Can we build this for ALL the devices?” with a resounding YES. This book will help you get there with a real-world introduction to seven platforms, whether you’re new to mobile or an experienced developer needing to expand your options. Plus, you’ll find out which cross-platform solution makes the most sense for your needs.

$26.00 
post /line_items?product_id=2
You are being redirected. 
get http://localhost:3000/carts/2

Your Cart

1× Rails, Angular, Postgres, and Bootstrap $45.00
Total $45.00

Add a few more products, and watch the totals climb!

post /line_items?product_id=2
You are being redirected. 
get http://localhost:3000/carts/2

Your Cart

2× Rails, Angular, Postgres, and Bootstrap $90.00
Total $90.00 
post /line_items?product_id=3
You are being redirected. 
get http://localhost:3000/carts/2

Your Cart

2× Rails, Angular, Postgres, and Bootstrap $90.00
1× Seven Mobile Apps in Seven Weeks $26.00
Total $116.00

10.4 Playtime 10.2 Iteration E2: Handling Errors