Rails：多步形式的动态 select 未保持 selected
Rails: dynamic select on multistep form not keeping selected
我正在按照 Ryan Bates Multistep Tutorial #217 使用会话的方式为订单下达流程制作多步骤表单。在第一步中，我有两个 select 字段：一个用于国家（陆地），一个动态用于运输服务。土地被 selected 后，通过 javascript/jQuery 将运输服务加载到第二个 select 字段，并通过 JS 计算总价。
app/views/orders/_shipping_step.html.erb
<%= f.collection_select(:land_id, Land.all, :id, :name, {:prompt => "select a country"}, {:id => 'lands_select'}) %>
<%= f.select(:shippingservice_id, options_for_select(@shippingservices.collect { |s| [s.name.titleize, s.id, {'data-price' => s.price}] }, :selected => f.object.shippingservice_id), {:prompt => "select a carrier"}, {:id => "shippingservices_select"}) %>
ajax 脚本
$(document).on("change", "#lands_select", function(event){
$.ajax({
url: "/carts/update_shipping/" + event.target.value,
type: "GET",
})
});
在multistep form的shipping details步骤我可以选择一个land，相应的shipment options被加载，我可以选择一个。当进行到付款步骤时，我可以下订单并且一切正常，但如果我想 return 从付款步骤到订单步骤进行更改，运输服务 select 或显示选项对于 land_id = 1，而土地 select 显示选择的国家，例如 id 85.
我已将 :selected => session[:cart_params] 添加到送货服务 select，但它似乎不起作用。 :selected => f.object.shippingservice_id 保留优先或标准运输选项，但 Land_id 1.
我怎样才能让它工作？是select字段还是JS？为什么第二个 select 不将选择的土地保存在内存中？
提前致谢！
日志：
Started GET "/orders/new" for 127.0.0.1 at Thu Dec 27 22:08:52 +0100 2018
Processing by OrdersController#new as HTML
Cart Load (0.3ms) SELECT `carts`.* FROM `carts` WHERE `carts`.`id` = ? LIMIT 1 [["id", 1]]
Land Load (1.4ms) SELECT `lands`.* FROM `lands`
CartItem Load (0.3ms) SELECT `cart_items`.* FROM `cart_items` WHERE `cart_items`.`cart_id` = 1
(0.2ms) SELECT MAX(`cart_items`.`length`) AS max_id FROM `cart_items` WHERE `cart_items`.`cart_id` = 1
(0.2ms) SELECT MAX(`cart_items`.`width`) AS max_id FROM `cart_items` WHERE `cart_items`.`cart_id` = 1
CACHE (0.0ms) SELECT `lands`.* FROM `lands`
Shippingservice Load (0.6ms) SELECT `shippingservices`.* FROM `shippingservices` INNER JOIN `zones` ON `zones`.`id` = `shippingservices`.`zone_id` INNER JOIN `lands_zones` ON `lands_zones`.`zone_id` = `zones`.`id` INNER JOIN `lands` ON `lands`.`id` = `lands_zones`.`land_id` WHERE `lands`.`id` = 1 AND (weightmin <= 50 AND weightmax >= 50 AND heightmin <= 3 AND heightmax >= 3 AND shippingservices.shippingcarrier = ‘1’) AND (lengthmax >= 210 AND widthmax >= 149)
Product Load (0.3ms) SELECT `products`.* FROM `products` WHERE `products`.`id` = 3 LIMIT 1
Hero Load (0.2ms) SELECT `heros`.* FROM `heros` WHERE `heros`.`id` = 18 LIMIT 1
Rendered orders/_shipping_step.html.erb (13.7ms)
Rendered orders/new.html.erb within layouts/application (16.2ms)
Rendered layouts/_header.html.erb (0.1ms)
Rendered layouts/_footer.html.erb (0.1ms)
Completed 200 OK in 44ms (Views: 23.0ms | ActiveRecord: 3.9ms)
选择运送国家：
Started GET "/carts/update_shipping/85" for 127.0.0.1 at Thu Dec 27 22:09:27 +0100 2018
Processing by CartsController#update_shipping as */*
Parameters: {"id"=>"85"}
Cart Load (0.2ms) SELECT `carts`.* FROM `carts` WHERE `carts`.`id` = ? LIMIT 1 [["id", 1]]
Land Load (66.9ms) SELECT `lands`.* FROM `lands`
CartItem Load (0.4ms) SELECT `cart_items`.* FROM `cart_items` WHERE `cart_items`.`cart_id` = 1
(0.2ms) SELECT MAX(`cart_items`.`length`) AS max_id FROM `cart_items` WHERE `cart_items`.`cart_id` = 1
(0.2ms) SELECT MAX(`cart_items`.`width`) AS max_id FROM `cart_items` WHERE `cart_items`.`cart_id` = 1
Shippingservice Load (0.6ms) SELECT `shippingservices`.* FROM `shippingservices` INNER JOIN `zones` ON `zones`.`id` = `shippingservices`.`zone_id` INNER JOIN `lands_zones` ON `lands_zones`.`zone_id` = `zones`.`id` INNER JOIN `lands` ON `lands`.`id` = `lands_zones`.`land_id` WHERE `lands`.`id` = 85 AND (weightmin <= 50 AND weightmax >= 50 AND heightmin <= 3 AND heightmax >= 3 AND shippingservices.shippingcarrier = ‘1’) AND (lengthmax >= 210 AND widthmax >= 149)
Rendered carts/_shippingservice.html.erb (0.2ms)
Rendered carts/update_shipping.js.erb (2.9ms)
Completed 200 OK in 87ms (Views: 7.8ms | ActiveRecord: 68.6ms)
正在进行下一步：
Started POST "/orders" for 127.0.0.1 at Thu Dec 27 22:09:33 +0100 2018
Processing by OrdersController#create as HTML
Parameters: {"order"=>{"ship_to_last_name"=>”surname”, "ship_to_address"=>”street”, "ship_to_city"=>”city”, "ship_to_postal_code"=>”postcode”, "phone_number"=>”somenumber”, "shippingservice_id"=>"27", "email"=>”something@example.tld”, "land_id"=>"85", "ship_to_first_name"=>”firstname”}, "authenticity_token"=>”somestring”, "utf8"=>"✓", "commit"=>"Continue"}
Cart Load (0.2ms) SELECT `carts`.* FROM `carts` WHERE `carts`.`id` = ? LIMIT 1 [["id", 1]]
Land Load (1.5ms) SELECT `lands`.* FROM `lands`
CartItem Load (0.4ms) SELECT `cart_items`.* FROM `cart_items` WHERE `cart_items`.`cart_id` = 1
(0.2ms) SELECT MAX(`cart_items`.`length`) AS max_id FROM `cart_items` WHERE `cart_items`.`cart_id` = 1
(0.2ms) SELECT MAX(`cart_items`.`width`) AS max_id FROM `cart_items` WHERE `cart_items`.`cart_id` = 1
Land Load (0.4ms) SELECT `lands`.* FROM `lands` WHERE `lands`.`id` = 85 LIMIT 1
Shippingservice Load (0.3ms) SELECT `shippingservices`.* FROM `shippingservices` WHERE `shippingservices`.`id` = 27 LIMIT 1
Product Load (0.3ms) SELECT `products`.* FROM `products` WHERE `products`.`id` = 3 LIMIT 1
Hero Load (0.3ms) SELECT `heros`.* FROM `heros` WHERE `heros`.`id` = 18 LIMIT 1
Rendered orders/_payment_step.html.erb (7.0ms)
Rendered orders/new.html.erb within layouts/application (8.9ms)
Rendered layouts/_header.html.erb (0.1ms)
Rendered layouts/_footer.html.erb (0.0ms)
Completed 200 OK in 39ms (Views: 13.7ms | ActiveRecord: 4.6ms)
返回到运输详细信息步骤：
Started POST "/orders" for 127.0.0.1 at Thu Dec 27 22:09:35 +0100 2018
Processing by OrdersController#create as HTML
Parameters: {"authenticity_token"=>”somestring”, "utf8"=>"✓", "back_button"=>"Back"}
Cart Load (0.3ms) SELECT `carts`.* FROM `carts` WHERE `carts`.`id` = ? LIMIT 1 [["id", 1]]
Land Load (2.4ms) SELECT `lands`.* FROM `lands`
CartItem Load (0.5ms) SELECT `cart_items`.* FROM `cart_items` WHERE `cart_items`.`cart_id` = 1
(0.3ms) SELECT MAX(`cart_items`.`length`) AS max_id FROM `cart_items` WHERE `cart_items`.`cart_id` = 1
(0.4ms) SELECT MAX(`cart_items`.`width`) AS max_id FROM `cart_items` WHERE `cart_items`.`cart_id` = 1
CACHE (0.0ms) SELECT `lands`.* FROM `lands`
Shippingservice Load (0.7ms) SELECT `shippingservices`.* FROM `shippingservices` INNER JOIN `zones` ON `zones`.`id` = `shippingservices`.`zone_id` INNER JOIN `lands_zones` ON `lands_zones`.`zone_id` = `zones`.`id` INNER JOIN `lands` ON `lands`.`id` = `lands_zones`.`land_id` WHERE `lands`.`id` = 1 AND (weightmin <= 50 AND weightmax >= 50 AND heightmin <= 3 AND heightmax >= 3 AND shippingservices.shippingcarrier = ‘1’) AND (lengthmax >= 210 AND widthmax >= 149)
Product Load (0.3ms) SELECT `products`.* FROM `products` WHERE `products`.`id` = 3 LIMIT 1
Hero Load (0.2ms) SELECT `heros`.* FROM `heros` WHERE `heros`.`id` = 18 LIMIT 1
Rendered orders/_shipping_step.html.erb (16.5ms)
Rendered orders/new.html.erb within layouts/application (18.4ms)
Rendered layouts/_header.html.erb (0.2ms)
Rendered layouts/_footer.html.erb (0.1ms)
Completed 200 OK in 109ms (Views: 24.0ms | ActiveRecord: 5.1ms)
更新
这是我的部分 orders_controller.rb
before_filter :initialize_cart
def new
session[:order_params] ||= {}
@order = Order.new(session[:order_params])
@order.current_step = session[:order_step]
@shippingservices = @cart.available_shipping_services.joins(:lands).where(:lands => {:id => session[:cart_params]})
end
def create
session[:order_params].deep_merge!(params[:order]) if params[:order]
@order = Order.new(session[:order_params])
@shippingservices = @cart.available_shipping_services.joins(:lands).where(:lands => {:id => session[:cart_params]})
@order.current_step = session[:order_step]
if @order.valid?
if params[:back_button]
@order.previous_step
elsif @order.last_step? && params[:commit] == 'Option A'
…
elsif @order.last_step? && params[:commit] == 'Option B'
…
else
@order.next_step
end
session[:order_step] = @order.current_step
end
if @order.new_record?
render "new"
else
# Empty the cart
@cart.cart_items.destroy_all
# Reset session
session[:order_step] = session[:order_params] = nil
end
end
当我通过 Land.first.id 或 Land.last.id 指定 id 时，查询有效并且后退步骤似乎有效。
当使用 session[:order_params] 时，我得到 ActiveRecord::StatementInvalid in Orders#create 但正确的 land_id 存在：
Mysql::Error: Unknown column 'id.ship_to_last_name' in 'where clause': SELECT `shippingservices`.* FROM `shippingservices`
INNER JOIN `zones` ON `zones`.`id` = `shippingservices`.`zone_id`
INNER JOIN `lands_zones` ON `lands_zones`.`zone_id` = `zones`.`id`
INNER JOIN `lands` ON `lands`.`id` = `lands_zones`.`land_id`
WHERE `id`.`ship_to_last_name` = 'Smith'
AND `id`.`ship_to_address` = 'Somewherestreet'
AND `id`.`ship_to_city` = 'Nowheretown'
AND `id`.`ship_to_postal_code` = '99999'
AND `id`.`phone_number` = 'some number'
AND `id`.`shippingservice_id` = '34'
AND `id`.`email` = 'someone@example.tld'
AND `id`.`land_id` = '85'
AND `id`.`ship_to_first_name` = 'John'
AND (weightmin <= 200 AND weightmax >= 200 AND heightmin <= 12 AND heightmax >= 12 AND shippingservices.shippingcarrier = '1') AND (lengthmax >= 210 AND widthmax >= 149)
@shippingservices = @cart.available_shipping_services.joins(:lands).where(:lands => {:id => session[:cart_params]})
这没有正确使用 session[:cart_params] 获取 land_id 以便在通过表格返回时设置订单降落。我们可以改用 @order = Order.new(session[:order_params]) 上面定义的一行来获取 @order.land_id 而不必依赖任何会话。
如果订单有可能在没有相应土地的情况下被初始化，我还会添加一个存在性检查。
我正在按照 Ryan Bates Multistep Tutorial #217 使用会话的方式为订单下达流程制作多步骤表单。在第一步中，我有两个 select 字段：一个用于国家（陆地），一个动态用于运输服务。土地被 selected 后，通过 javascript/jQuery 将运输服务加载到第二个 select 字段，并通过 JS 计算总价。
app/views/orders/_shipping_step.html.erb
<%= f.collection_select(:land_id, Land.all, :id, :name, {:prompt => "select a country"}, {:id => 'lands_select'}) %>
<%= f.select(:shippingservice_id, options_for_select(@shippingservices.collect { |s| [s.name.titleize, s.id, {'data-price' => s.price}] }, :selected => f.object.shippingservice_id), {:prompt => "select a carrier"}, {:id => "shippingservices_select"}) %>
ajax 脚本
$(document).on("change", "#lands_select", function(event){
$.ajax({
url: "/carts/update_shipping/" + event.target.value,
type: "GET",
})
});
在multistep form的shipping details步骤我可以选择一个land，相应的shipment options被加载，我可以选择一个。当进行到付款步骤时，我可以下订单并且一切正常，但如果我想 return 从付款步骤到订单步骤进行更改，运输服务 select 或显示选项对于 land_id = 1，而土地 select 显示选择的国家，例如 id 85.
我已将 :selected => session[:cart_params] 添加到送货服务 select，但它似乎不起作用。 :selected => f.object.shippingservice_id 保留优先或标准运输选项，但 Land_id 1.
我怎样才能让它工作？是select字段还是JS？为什么第二个 select 不将选择的土地保存在内存中？
提前致谢！
日志：
Started GET "/orders/new" for 127.0.0.1 at Thu Dec 27 22:08:52 +0100 2018
Processing by OrdersController#new as HTML
Cart Load (0.3ms) SELECT `carts`.* FROM `carts` WHERE `carts`.`id` = ? LIMIT 1 [["id", 1]]
Land Load (1.4ms) SELECT `lands`.* FROM `lands`
CartItem Load (0.3ms) SELECT `cart_items`.* FROM `cart_items` WHERE `cart_items`.`cart_id` = 1
(0.2ms) SELECT MAX(`cart_items`.`length`) AS max_id FROM `cart_items` WHERE `cart_items`.`cart_id` = 1
(0.2ms) SELECT MAX(`cart_items`.`width`) AS max_id FROM `cart_items` WHERE `cart_items`.`cart_id` = 1
CACHE (0.0ms) SELECT `lands`.* FROM `lands`
Shippingservice Load (0.6ms) SELECT `shippingservices`.* FROM `shippingservices` INNER JOIN `zones` ON `zones`.`id` = `shippingservices`.`zone_id` INNER JOIN `lands_zones` ON `lands_zones`.`zone_id` = `zones`.`id` INNER JOIN `lands` ON `lands`.`id` = `lands_zones`.`land_id` WHERE `lands`.`id` = 1 AND (weightmin <= 50 AND weightmax >= 50 AND heightmin <= 3 AND heightmax >= 3 AND shippingservices.shippingcarrier = ‘1’) AND (lengthmax >= 210 AND widthmax >= 149)
Product Load (0.3ms) SELECT `products`.* FROM `products` WHERE `products`.`id` = 3 LIMIT 1
Hero Load (0.2ms) SELECT `heros`.* FROM `heros` WHERE `heros`.`id` = 18 LIMIT 1
Rendered orders/_shipping_step.html.erb (13.7ms)
Rendered orders/new.html.erb within layouts/application (16.2ms)
Rendered layouts/_header.html.erb (0.1ms)
Rendered layouts/_footer.html.erb (0.1ms)
Completed 200 OK in 44ms (Views: 23.0ms | ActiveRecord: 3.9ms)
选择运送国家：
Started GET "/carts/update_shipping/85" for 127.0.0.1 at Thu Dec 27 22:09:27 +0100 2018
Processing by CartsController#update_shipping as */*
Parameters: {"id"=>"85"}
Cart Load (0.2ms) SELECT `carts`.* FROM `carts` WHERE `carts`.`id` = ? LIMIT 1 [["id", 1]]
Land Load (66.9ms) SELECT `lands`.* FROM `lands`
CartItem Load (0.4ms) SELECT `cart_items`.* FROM `cart_items` WHERE `cart_items`.`cart_id` = 1
(0.2ms) SELECT MAX(`cart_items`.`length`) AS max_id FROM `cart_items` WHERE `cart_items`.`cart_id` = 1
(0.2ms) SELECT MAX(`cart_items`.`width`) AS max_id FROM `cart_items` WHERE `cart_items`.`cart_id` = 1
Shippingservice Load (0.6ms) SELECT `shippingservices`.* FROM `shippingservices` INNER JOIN `zones` ON `zones`.`id` = `shippingservices`.`zone_id` INNER JOIN `lands_zones` ON `lands_zones`.`zone_id` = `zones`.`id` INNER JOIN `lands` ON `lands`.`id` = `lands_zones`.`land_id` WHERE `lands`.`id` = 85 AND (weightmin <= 50 AND weightmax >= 50 AND heightmin <= 3 AND heightmax >= 3 AND shippingservices.shippingcarrier = ‘1’) AND (lengthmax >= 210 AND widthmax >= 149)
Rendered carts/_shippingservice.html.erb (0.2ms)
Rendered carts/update_shipping.js.erb (2.9ms)
Completed 200 OK in 87ms (Views: 7.8ms | ActiveRecord: 68.6ms)
正在进行下一步：
Started POST "/orders" for 127.0.0.1 at Thu Dec 27 22:09:33 +0100 2018
Processing by OrdersController#create as HTML
Parameters: {"order"=>{"ship_to_last_name"=>”surname”, "ship_to_address"=>”street”, "ship_to_city"=>”city”, "ship_to_postal_code"=>”postcode”, "phone_number"=>”somenumber”, "shippingservice_id"=>"27", "email"=>”something@example.tld”, "land_id"=>"85", "ship_to_first_name"=>”firstname”}, "authenticity_token"=>”somestring”, "utf8"=>"✓", "commit"=>"Continue"}
Cart Load (0.2ms) SELECT `carts`.* FROM `carts` WHERE `carts`.`id` = ? LIMIT 1 [["id", 1]]
Land Load (1.5ms) SELECT `lands`.* FROM `lands`
CartItem Load (0.4ms) SELECT `cart_items`.* FROM `cart_items` WHERE `cart_items`.`cart_id` = 1
(0.2ms) SELECT MAX(`cart_items`.`length`) AS max_id FROM `cart_items` WHERE `cart_items`.`cart_id` = 1
(0.2ms) SELECT MAX(`cart_items`.`width`) AS max_id FROM `cart_items` WHERE `cart_items`.`cart_id` = 1
Land Load (0.4ms) SELECT `lands`.* FROM `lands` WHERE `lands`.`id` = 85 LIMIT 1
Shippingservice Load (0.3ms) SELECT `shippingservices`.* FROM `shippingservices` WHERE `shippingservices`.`id` = 27 LIMIT 1
Product Load (0.3ms) SELECT `products`.* FROM `products` WHERE `products`.`id` = 3 LIMIT 1
Hero Load (0.3ms) SELECT `heros`.* FROM `heros` WHERE `heros`.`id` = 18 LIMIT 1
Rendered orders/_payment_step.html.erb (7.0ms)
Rendered orders/new.html.erb within layouts/application (8.9ms)
Rendered layouts/_header.html.erb (0.1ms)
Rendered layouts/_footer.html.erb (0.0ms)
Completed 200 OK in 39ms (Views: 13.7ms | ActiveRecord: 4.6ms)
返回到运输详细信息步骤：
Started POST "/orders" for 127.0.0.1 at Thu Dec 27 22:09:35 +0100 2018
Processing by OrdersController#create as HTML
Parameters: {"authenticity_token"=>”somestring”, "utf8"=>"✓", "back_button"=>"Back"}
Cart Load (0.3ms) SELECT `carts`.* FROM `carts` WHERE `carts`.`id` = ? LIMIT 1 [["id", 1]]
Land Load (2.4ms) SELECT `lands`.* FROM `lands`
CartItem Load (0.5ms) SELECT `cart_items`.* FROM `cart_items` WHERE `cart_items`.`cart_id` = 1
(0.3ms) SELECT MAX(`cart_items`.`length`) AS max_id FROM `cart_items` WHERE `cart_items`.`cart_id` = 1
(0.4ms) SELECT MAX(`cart_items`.`width`) AS max_id FROM `cart_items` WHERE `cart_items`.`cart_id` = 1
CACHE (0.0ms) SELECT `lands`.* FROM `lands`
Shippingservice Load (0.7ms) SELECT `shippingservices`.* FROM `shippingservices` INNER JOIN `zones` ON `zones`.`id` = `shippingservices`.`zone_id` INNER JOIN `lands_zones` ON `lands_zones`.`zone_id` = `zones`.`id` INNER JOIN `lands` ON `lands`.`id` = `lands_zones`.`land_id` WHERE `lands`.`id` = 1 AND (weightmin <= 50 AND weightmax >= 50 AND heightmin <= 3 AND heightmax >= 3 AND shippingservices.shippingcarrier = ‘1’) AND (lengthmax >= 210 AND widthmax >= 149)
Product Load (0.3ms) SELECT `products`.* FROM `products` WHERE `products`.`id` = 3 LIMIT 1
Hero Load (0.2ms) SELECT `heros`.* FROM `heros` WHERE `heros`.`id` = 18 LIMIT 1
Rendered orders/_shipping_step.html.erb (16.5ms)
Rendered orders/new.html.erb within layouts/application (18.4ms)
Rendered layouts/_header.html.erb (0.2ms)
Rendered layouts/_footer.html.erb (0.1ms)
Completed 200 OK in 109ms (Views: 24.0ms | ActiveRecord: 5.1ms)
更新
这是我的部分 orders_controller.rb
before_filter :initialize_cart
def new
session[:order_params] ||= {}
@order = Order.new(session[:order_params])
@order.current_step = session[:order_step]
@shippingservices = @cart.available_shipping_services.joins(:lands).where(:lands => {:id => session[:cart_params]})
end
def create
session[:order_params].deep_merge!(params[:order]) if params[:order]
@order = Order.new(session[:order_params])
@shippingservices = @cart.available_shipping_services.joins(:lands).where(:lands => {:id => session[:cart_params]})
@order.current_step = session[:order_step]
if @order.valid?
if params[:back_button]
@order.previous_step
elsif @order.last_step? && params[:commit] == 'Option A'
…
elsif @order.last_step? && params[:commit] == 'Option B'
…
else
@order.next_step
end
session[:order_step] = @order.current_step
end
if @order.new_record?
render "new"
else
# Empty the cart
@cart.cart_items.destroy_all
# Reset session
session[:order_step] = session[:order_params] = nil
end
end
当我通过 Land.first.id 或 Land.last.id 指定 id 时，查询有效并且后退步骤似乎有效。
当使用 session[:order_params] 时，我得到 ActiveRecord::StatementInvalid in Orders#create 但正确的 land_id 存在：
Mysql::Error: Unknown column 'id.ship_to_last_name' in 'where clause': SELECT `shippingservices`.* FROM `shippingservices`
INNER JOIN `zones` ON `zones`.`id` = `shippingservices`.`zone_id`
INNER JOIN `lands_zones` ON `lands_zones`.`zone_id` = `zones`.`id`
INNER JOIN `lands` ON `lands`.`id` = `lands_zones`.`land_id`
WHERE `id`.`ship_to_last_name` = 'Smith'
AND `id`.`ship_to_address` = 'Somewherestreet'
AND `id`.`ship_to_city` = 'Nowheretown'
AND `id`.`ship_to_postal_code` = '99999'
AND `id`.`phone_number` = 'some number'
AND `id`.`shippingservice_id` = '34'
AND `id`.`email` = 'someone@example.tld'
AND `id`.`land_id` = '85'
AND `id`.`ship_to_first_name` = 'John'
AND (weightmin <= 200 AND weightmax >= 200 AND heightmin <= 12 AND heightmax >= 12 AND shippingservices.shippingcarrier = '1') AND (lengthmax >= 210 AND widthmax >= 149)
@shippingservices = @cart.available_shipping_services.joins(:lands).where(:lands => {:id => session[:cart_params]})
这没有正确使用 session[:cart_params] 获取 land_id 以便在通过表格返回时设置订单降落。我们可以改用 @order = Order.new(session[:order_params]) 上面定义的一行来获取 @order.land_id 而不必依赖任何会话。
如果订单有可能在没有相应土地的情况下被初始化，我还会添加一个存在性检查。