ruby on rails(10) --- 订单处理

   订单处理，首先要有一个订单的详细列表（包括数量，价格啥的）和一个关于个人的一些信息的一个表。因此我们创建两个模型，line_item(列表项),order(列表)，然后编辑如下
/db/migrate xxx_create_order xxx_line_item

  class CreateOrders < ActiveRecord::Migration
  def self.up
    create_table :orders do |t|
			t.string :name
			t.text   :address
			t.string :email
			t.string :pay_type, :limit => 10
      t.timestamps
    end
  end

  def self.down
    drop_table :orders
  end
end

   class CreateLineItems < ActiveRecord::Migration
  def self.up
    create_table :line_items do |t|
      t.integer :product_id, :null => false,:options =>
      "CONSTRAINT fk_line_items_products REFERENCES products(id)"
      t.integer :order_id,:null => false, :options =>
      "CONSTRAINT fk_line_items_orders ReEFERENCES orders(id)"
      t.integer :quantity, :null => false
      t.decimal :total_price, :null => false,:precision => 8,:scale => 2
      t.timestamps
    end
  end

  def self.down
    drop_table :line_items
  end
end

t.integer :product_id, :null => false,:options =>
      "CONSTRAINT fk_line_items_products REFERENCES products(id)"
,对product_id进行约束,其范围只能在products 表的id中选
数据库中两者的关系已经清楚，接下来在rails中建立关系

class Order < ActiveRecord::Base
	has_many :line_items   #包含子集

class LineItem < ActiveRecord::Base
	belongs_to :order   #有外键就用belogns_to,表示LineItem是这两者的
	belongs_to :product  #子集，只有父存在，只才存在。

   这样三者就可以相互引用。

放置一个checkout 按钮，然后定义其方法
<%=button_to "Checkout",:action => :checkout%> ----_cart.html.erb
/app/controller/store_controller.rb
  def checkout
    @cart = find_cart
    if @cart.items.empty?
      rediret_to_index("Your cart is empty")
     else
      @order = Order.new
     end
  end
#如果购物车里有东西，则生成一个订单

关联数据
form_for 可以使view 通过controller中与model对应的数据，这样分析对么

<div id="depot-form">
	<%= error_messages_for "order"%>
	<fieldset>
	<legend>Please Enter Your Details</legend>
             
	<%form_for :order, :url => {:action => :save_order} do |f|%>
                  
                  <p>
		<%=label :order,:name,"Name:"%>
			<%= f.text_field :name,:size => 40%>
		</p>
				<p>
			<%= label :order,:pay_type, "Pay_with:"%>
			<%= f.select :pay_type, 			                    Order::PAYMENT_TYPES,
		:promt => "Select a payment type"
		    %>
		</p>
		<%= submit_tag "Place Order",:class => "submit" %>
		<%end%>
	</fieldset>
</div>

#:order 对应controller中的@order,而下面的参数如name取得则是model里面的
困了，后面就贴代码

/model/order

	PAYMENT_TYPES = [
		#Display  Store in db
		["Check","check"],
		["Credit Cart","cc"],
		["Purchase Order","po"]
	]
	
	validates_presence_of :name,:address,:email,:pay_type
	validates_inclusion_of :pay_type,:in => PAYMENT_TYPES.map{|dispay,value|value}

store_controller

def save_order
    @cart  = find_cart 
    @order = Order.new(params[:order])
    @order.add_line_items_from_cart(@cart)
    if @order.save  #save哪里来的
      session[:cart] = nil
      redirect_to_index("Thank you for your order")
    else
      render :action => :checkout
    end
  end

order.rb

def add_line_items_from_cart(cart)
		cart.items.each do |item|
			li = LineItem.from_cart_item(item)
			line_items << li
		end
	end

line_items << li因为用到上面的has_many
/models/line_items.rb

def self.from_cart_item(cart_item)
		li = self.new
		li.product = cart_item.product
		li.quantity = cart_item.quantity
		li.total_price = cart_item.price
		li
end

时间不早了，11.36了，洗洗睡吧