Rails 4.2 - 如何构建 has_many，通过：与 collection_select 关联

Question

我目前正在使用带有这些模型的 Rails 4.2：

class User < ActiveRecord::Base
  has_many :user_accessories, dependent: :destroy
  accepts_nested_attributes_for :user_accessories,
    reject_if: :all_blank,
    allow_destroy: true
  has_many :accessories, through: :user_accessories
end

class UserAccessory < ActiveRecord::Base
  belongs_to :user,      required: true
  belongs_to :accessory, required: true
end

class Accessory < ActiveRecord::Base
  has_many :user_accessories, dependent: :destroy
  has_many :users, through: :user_accessories
end

这是一种简单的多对多关系，其中一个用户可以“拥有”许多配件，而一个配件可以被多个用户“拥有”。

我已按以下方式设置路线：

resources :users, only: [ :index, :show, :edit, :update, :accessories ] do
  member do
    get 'accessories'
  end
end

这样，用户可以转到他们的“配件”路径 (/users/1/accessories) 来查看他们的配件列表，以及向他们的帐户添加新的配件关联。

这是为附件路径呈现的视图：

<table>
  <thead>
    <tr>
      <th>Name</th>
    </tr>
  </thead>
  <tbody>
    <%= render @accessories %>
  </tbody>
</table>

<%= form_for( @user ) do |f| %>
  <%= f.collection_select( 
    :accessory_ids, 
    Accessory.all, 
    :id, 
    :name, { include_hidden: false }, { multiple: true } ) 
  %>

  <%= f.button "Add Equipment" %>
<% end %>

这只是渲染当前配件的表格，然后构建一个 collection_select 框，您可以在其中选择要添加的多个配件。我通过删除 Bootstrap 样式简化了这一点。

最后，以下是相关的控制器操作：

def update
  @user = User.find( params[:id] )
  if( @user.update_attributes( update_params ) )
    redirect_to @user
  else
    render 'edit'
  end
end

def accessories 
  @user = User.find( params[:id] ) 
  @accessories = @user.accessories 
end 

private 
  def update_params 
    params.require( :user ).permit( 
      :first_name, 
      :last_name, 
      :region_id, 
      :country, 
      :profile_image, 
      :remove_profile_image, 
      accessory_ids: [:id], 
    )
  end

现在的问题：

1. 当我已经在数据库中手动输入了一个值时提交表单实际上只是删除 所有 当前存储的值并且不添加任何新值：

   Started PATCH "/users/nuggles" for 127.0.0.1 at 2015-02-18 13:31:50 -0500
   
   Processing by UsersController#update as HTML
   
   Parameters: {
     "utf8"=>"✓",····
     "authenticity_token"=>"my_token",·
     "user"=>{
       "accessory_ids"=>["5"]
     },· 
     "button"=>"",·
     "id"=>"nuggles"
   } 
   
   User Load (40.0ms)  SELECT  "users".* FROM "users" WHERE "users"."id" = $1  ORDER BY "users"."id" ASC LIMIT 1  [["id", 4]] 
   
   User Load (36.4ms)  SELECT  "users".* FROM "users" WHERE "users"."slug" = $1  ORDER BY "users"."id" ASC LIMIT 1  [["slug", "nuggles"]]·
   
   (33.5ms)  BEGIN
   
   Accessory Load (34.1ms)  SELECT "accessories".* FROM "accessories" INNER JOIN "user_accessories" ON "accessories"."id" = "user_accessories"."accessory_id" WHERE "user_accessories"."user_id" = $1  [["user_id", 4]]
   
   **SQL (34.1ms)  DELETE FROM "user_accessories" WHERE "user_accessories"."user_id" = $1 AND "user_accessories"."accessory_id" IN (1, 2, 3)  [["user_id", 4]]**
   
   User Exists (37.7ms)  SELECT  1 AS one FROM "users" WHERE (LOWER("users"."username") = LOWER('Nuggles') AND "users"."id" != 4) LIMIT 1
   
   (34.2ms)  COMMIT
   
   Redirected to http://localhost:3000/users/nuggles
   Completed 302 Found in 304ms (ActiveRecord: 250.0ms)
   

2. 提交未选择任何内容的表单时，我收到以下错误：

   param is missing or the value is empty: user
   
   private
     def update_params
       params.require( :user ).permit(
         :first_name,
         :last_name,
         :region_id,
   

Answer 1

对于任何感兴趣的人，我的表格都可以使用。这可能不是一次创建多条记录的理想方式，但它现在对我有用。

首先，我在Users 控制器中取出了奇怪的accessories 定义。由于我将直接创建、更新和销毁用户的附件，因此连接模型应该有自己的控制器：

class UserAccessoriesController < ApplicationController
  def index
    @user = User.friendly.find( params[:id] )
    @user_accessories = @user.user_accessories
  end

  def create
    @user = User.friendly.find( params[:id] )

    create_params[:accessory].each do |accessory|
      @user_accessory = UserAccessory.new( user: @user, accessory_id: accessory )

      @user_accessory.save
    end

    redirect_to user_accessories_path( @user )
  end

  def destroy
    @user_accessory = UserAccessory.friendly.find( params[:id] )

    @user_accessory.destroy
  end

  private
    def create_params
      params.require( :user_accessory ).permit(
        :id,
        accessory: []
      )
    end
end

对于UserAccessories，我只有一个视图，即索引。该页面列出了一个用户的所有配件，如果显示的用户与登录的用户相同，则显示如下表格：

  <%= form_for @user_accessories.new(), { method: :post } do |f| %>
    <div class="form-group">
      <%= f.collection_select(
                               :accessory,
                               # Get only accessories not on the user's account
                               Accessory.where.not( id: @user.accessories ),
                               :id,
                               :name,
                               {
                                 include_hidden: false
                               },
                               {
                                 multiple:    true,
                                 class:       'form-control',
                                 placeholder: 'Select Equipment to Add'
                               }
                             ) %>
    </div>

    <div class="form-group">
      <%= f.submit "Update Equipment" %>
    </div>
  <% end %>

这允许用户选择多个附件（使用select2），然后在提交时在控制器中一一创建关联。

如果有人有更好的创建用户附件的方法（即不循环通过我的参数并创建多次），那么请发表评论！