在上次的内容里，我们实现了清空购物车和金额的格式化处理。这次实现订单的模块。

1.         首先，我们要在数据库里创建Order表，创建表的Sql如下：

create table orders (

id int not null auto_increment,

name varchar(100) not null,

email varchar(255) not null,

address text not null,

pay_type char(10) not null,

primary key (id)

);

    我们还要重新创建line_item表，下面是Sql：

create table line_items (

id int not null auto_increment,

product_id int not null,

order_id int not null,

quantity int not null default 0,

unit_price decimal(10,2) not null,

constraint fk_items_product foreign key (product_id) references products(id),

constraint fk_items_order foreign key (order_id) references orders(id),

primary key (id)

);

在InstantRail里，可以使用phpMyAdmin来执行Sql。

class Order < ActiveRecord::Base

has_many :line_items

PAYMENT_TYPES = [

[ "Check", "check" ],

[ "Credit Card", "cc" ],

[ "Purchase Order", "po" ]

].freeze

end

class LineItem < ActiveRecord::Base

belongs_to :product

belongs_to :order

def self.for_product(product) self.new

  item = self.new

  item.quantity = 1

  item.product = product

  item.unit_price = product.price

  item

end

end

可以看出，上面的修改其实就是给Order和LineItem之间添加了主从关系。

2.       给store_controller添加代码：

def checkout

@cart = find_cart

@items = @cart.items

if @items.empty?

redirect_to_index("There's nothing in your cart!")

else

@order = Order.new

end

end

3.       现在Model和Controller都有了，下面要作什么已经很明显了，当然是添加一个View了，在rails_apps\depot\app\views\store目录下创建checkout.rhtml文件，内容为：

<% @page_title = "Checkout" -%>

<%= start_form_tag(:action => "save_order") %>

    <table>

            <tr>

            <td>Name:</td>

            <td><%= text_field("order", "name", "size" => 40 ) %></td>

            </tr>

            <tr>

                    <td>EMail:</td>

                    <td><%= text_field("order", "email", "size" => 40 ) %></td>

            </tr>

            <tr valign="top">

                    <td>Address:</td>

                    <td><%= text_area("order", "address", "cols" => 40, "rows" => 5) %></td>

            </tr>

            <tr>

                    <td>Pay using:</td>

                    <td><%=

                            options = [["Select a payment option", ""]] + Order::PAYMENT_TYPES

                            select("order", "pay_type", options)

                    %></td>

            </tr>

            <tr>

                    <td></td>

                    <td><%= submit_tag(" CHECKOUT ") %></td>

            </tr>

    </table>

<%= end_form_tag %>

4.       这时候，如果打开Checkout页面的话，会显示错误页面，少了什么呢?我们还需要在order.rb文件中添加代码：

PAYMENT_TYPES = [

  [ "Check", "check" ],

  [ "Credit Card", "cc" ],

  [ "Purchase Order", "po" ]

  ].freeze

现在点击CHECKOUT按钮，会转到Rails的一个错误页面，提示“Unknown action”。下次我们实现这个功能。