问Rails 4库存应用程序:数据库设计和嵌套表单的使用

EN

#app/models/inventory.rb
class Inventory < ActiveRecord::Base
   # id | device_id | location_id | qty | created_at | updated_at
   belongs_to :device
   belongs_to :location
end

#app/models/device.rb
class Device < ActiveRecord::Base
   has_many :inventories
   has_many :locations, through: :inventories
   accepts_nested_attributes_for :inventories
end

#app/models/location.rb
class Location < ActiveRecord::Base
   has_many :inventories
   has_many :devices, through: :inventories
end

#app/controllers/devices_controller.rb
class DevicesController < ApplicationController 
   def new
     @device = Device.new
     @locations = Location.all
   end

   def create
     @device = Device.new device_params
     @device.save
   end

   private

   def device_params
     params.require(:device).permit(inventories_attributes: [:qty])
   end
end

#app/views/devices/new.html.erb
<%= form_for @device do |f| %>
  <%= f.text_field :name %>
  <%= f.fields_for :inventories, Location.all do |i| %>
     <%= i.number_field :qty %>
  <% end %>
  <%= f.submit %>
<% end %>