同一模型的不同实例（多个 has_many 通过关联）

Question

我在我的项目中有多个 has_many through 关系，并且正在寻求有关如何使用表单更新值的帮助。

有两种基本模型：产品和国家。一种产品可以来自多个原产国，也可以有多个目的地国家。（我想不出一个很好的例子来比喻）

create_table "nations", force: :cascade do |t|
  t.string "name"
end

create_table "products", force: :cascade do |t|
  t.string "name"
  t.string "bio"
end

create_table "dest_nation", force: :cascade do |t|
  t.integer "product_id"
  t.integer "nation_id"
end

create_table "orig_nation", force: :cascade do |t|
  t.integer "product_id"
  t.integer "nation_id"
end

然后我创建了如下关系：

class Product < ActiveRecord::Base
  has_many :dest_nations
  has_many :destination, :class_name=> 'nations', through: :dest_nation
  has_many :orig_nations
  has_many :origin, :class_name=> 'nations', through: :orig_nations 
end

class Nation < ActiveRecord::Base
  has_many :dest_nations
  has_many :imports, :class_name => 'products', through: :dest_nation
  has_many :orig_nations
  has_many :exports, :class_name =>'products', through: :orig_nations 
end

class DestNation < ActiveRecord::Base
  belongs_to :nation
  belongs_to :product
end

class OrigNation < ActiveRecord::Base
  belongs_to :nation
  belongs_to :product
end

问题： 1.) 注册产品时，我想知道用户可以从选项列表中 select 的来源国家和目的地国家/地区。我如何在视图和控制器中进行这些更改以适当地反映这些更改。

<%= form_for @product do |f|%>
  <div class="form-group">
    <%= f.label :name, "Name of the product:"%>
    <%= f.text_field :name, class: "form-control" %>
  </div>
  <div class="form-group">
    <%= f.label :bio, "A brief summary:"%>
    <%= f.text_area :bio, class: "form-control", rows:3%>
  </div>
  <!-- For origination country -->
  <%= f.collection_check_boxes :nation_ids, Nation.all, :id, :name do |cb|%>
    <% cb.label(class: "checkbox-inline input_checkbox") {cb.check_box(class: "checkbox") + cb.text}%>
  <% end %>
  <br>
<!-- For destination country -->
  <%= f.collection_check_boxes :nation_ids, Nation.all, :id, :name do |cb1|%>
    <% cb1.label(class: "checkbox-inline input_checkbox") {cb1.check_box(class: "checkbox") + cb1.text}%>
  <% end %>
  <br>                  
<%= f.submit "Submit", class: "btn btn-default btn-primary" %> 
<%end%>

我的产品控制器是

def create
  @product = Product.new(product_params)
  if @product.save
    flash[:success] = ""
    redirect_to root_path
  else
    render 'new'
  end    
  # binding pry
end

def product_params
  params.require(:product).permit(:name,:bio, nation_ids: [])
end

Answer 1

A product can be sourced from multiple origin countries and have multiple destination countries

听起来您正在寻找 has_and_belongs_to_many 协会：

这将使您的问题更容易处理：

#app/models/product.rb
class Product < ActiveRecord::Base
   has_and_belongs_to_many :destinations,
      :class_name =>"Nation",
      join_table: :destinations,
      foreign_key: :product_id,
      association_foreign_key: :nation_id

   has_and_belongs_to_many :origins, 
      :class_name =>"Nation",
      join_table: :origins,
      foreign_key: :product_id,
      association_foreign_key: :nation_id
end

#app/models/nation.rb
class Nation < ActiveRecord::Base
   has_and_belongs_to_many :exports, 
      :class_name=> "Product",
      join_table: :origins,
      foreign_key: :nation_id,
      association_foreign_key: :product_id

   has_and_belongs_to_many :imports, 
      :class_name=> "Product",
      join_table: :destinations,
      foreign_key: :nation_id,
      association_foreign_key: :product_id
end

你必须用下表来支持这些：

create_table "destinations", id: false do |t|
  t.integer "product_id"
  t.integer "nation_id"
end

create_table "origins", id:false do |t|
  t.integer "product_id"
  t.integer "nation_id"
end

How I can make those changes in the view and the controller to appropriately reflect these changes

#app/controllers/products_controller.rb
class ProductsController < ApplicationController
   def new
       @product = Product.new
   end

   def create
       @product = Product.new(product_params)
   end

   private

   def product_params
      params.require(:product).permit(:x, :y, :origins, :destinations)
   end
end

#app/views/products/new.html.erb
<%= form_for @product do |f|%>
   <%= f.collection_check_boxes :origins, Nation.all, :id, :name %>
   <%= f.submit %>
<% end %>

Answer 2

终于找到解决办法了。

此处仅列出答案部分的编辑内容

model/product.rb

class Product < ActiveRecord::Base
  has_many :dest_nations
  has_many :destinations, through: :dest_nations, :source => 'nation'
  has_many :orig_nations
  has_many :origins, through: :orig_nations, :source => 'nation'
end

对 nation.rb

进行了类似的更改

The form snippet reads (new.html.erb)

<%= f.collection_check_boxes :origin_ids, Nation.all, :id, :name do |cb1|%>
<% cb1.label(class: "checkbox-inline input_checkbox") {cb1.check_box(class: "checkbox") + cb1.text}%>

Finally the product params is updated as follows (in the products_controller.rb)

params.require(:product).permit(:name,:bio, origin_ids: [], destination_ids: [])

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