has_many通过和联接表

问题描述

我有以下型号：产品，零件和产品零件

product.rb

class Product < ApplicationRecord
  has_many :product_parts
  has_many :parts,through: :product_parts
  accepts_nested_attributes_for :product_parts,allow_destroy: true
end

part.rb

class Part < ApplicationRecord
  has_many :product_parts
  has_many :products,through: :product_parts
end

product_part.rb

class ProductPart < ApplicationRecord
  belongs_to :part
  belongs_to :product
end

该产品可能由几个部分组成，例如product1 = 1pcs part2和3pcs part 3。

我有联接表：product_parts

  create_table "product_parts",force: :cascade do |t|
    t.integer "part_id"
    t.integer "product_id"
    t.integer "quantity"
    t.index ["part_id"],name: "index_product_parts_on_part_id"
    t.index ["product_id"],name: "index_product_parts_on_product_id"
  end

我想为新产品呈现简单的表单，其中：

• 我可以输入产品名称
• 从所有零件中选择零件并定义每个零件数量

我有这样的_form.html.slim：

= simple_form_for(@product) do |f|
  = f.error_notification
  = f.error_notification message: f.object.errors[:base].to_sentence if f.object.errors[:base].present?
  = f.input :name
  = f.simple_fields_for :parts do |part|
    = f.label :part.name
    = f.input :part.quantity
  = f.button :submit

但是它不会渲染任何东西。您有任何提示以正确的方式进行操作吗？

我也试图这样做：

_form.html.slim

= simple_form_for(@product) do |f|
  = f.input :name
  = f.simple_fields_for :parts do |part|
    == render 'part_fields'
  = f.button :submit

_part_fields.html.slim

= :name
= part.input :quantity

服务器日志输出为：

17:34:21 web.1       | Started GET "/products/new" for ::1 at 2020-08-24 17:34:21 +0200
17:34:21 web.1       | Processing by ProductsController#new as HTML
17:34:21 web.1       |   Rendering products/new.html.slim within layouts/application
17:34:21 web.1       |   Part Load (0.1ms)  SELECT "parts".* FROM "parts" LIMIT ?  [["LIMIT",11]]
17:34:21 web.1       |   ↳ app/views/products/_form.html.slim:6
17:34:21 web.1       |   CACHE Part Load (0.0ms)  SELECT "parts".* FROM "parts" LIMIT ?  [["LIMIT",11]]
17:34:21 web.1       |   ↳ app/views/products/_form.html.slim:6
17:34:21 web.1       |   Rendered products/_part_fields.html.slim (Duration: 442.5ms | Allocations: 233999)
17:34:21 web.1       |   Rendered products/_form.html.slim (Duration: 449.1ms | Allocations: 240331)
17:34:21 web.1       |   Rendered products/new.html.slim within layouts/application (Duration: 451.5ms | Allocations: 242361)
17:34:21 web.1       | Completed 500 Internal Server Error in 454ms (ActiveRecord: 0.4ms | Allocations: 243658)
17:34:21 web.1       |
17:34:21 web.1       |
17:34:21 web.1       |
17:34:21 web.1       | ActionView::Template::Error - undefined local variable or method `part' for #<#<Class:0x00007f938cd03f28>:0x00007f938cd020b0>
17:34:21 web.1       | Did you mean?  @parts:
17:34:21 web.1       |   app/views/products/_part_fields.html.slim:2:in `view template'

谢谢大家的回答。我在GitHub上找到了示例： rails-recipes。现在我正在使用cocoon gem，并且我几乎在想要的地方：)但是：

_form.html.slim

= simple_form_for(@product) do |f|
  = f.input :name
  |Parts
  fieldset#parts
    = f.simple_fields_for :product_parts do |product_part|
      == render 'product_part_fields',f: product_part
      = link_to_add_association 'Add part',f,:product_parts,class: 'btn btn-primary btn-xs'
    = f.button :submit

_product_part.html.slim：

.nested_fields.field
  = f.input :quantity
  = f.collection_select :part_id,Part.all,:id,:name
  = link_to_remove_association f

渲染表单时，我已经有两部分输入，而不是一个（这应该是正确的）。 我不想创建新零件，只需从列表中选择零件并仅插入数量即可。 看起来像这样： screenshot of rendered form

产品未创建，在重新加载表单后，我将始终拥有2部分的字段。 这是控制台日志：

12:58:14 web.1       | Started POST "/products" for ::1 at 2020-08-28 12:58:14 +0200
12:58:14 web.1       | Processing by ProductsController#create as HTML
12:58:14 web.1       |   Parameters: {"authenticity_token"=>"dLVq3gUUeHnmFgVxQ7gXATOF3wdQ75a/csjmjzYN6HFrr9duoi50M4KzrSUNj/QHCrJgXO2myJPdpkybdTB0cA==","product"=>{"name"=>"Product #1","product_parts_attributes"=>{"0"=>{"quantity"=>"4","part_id"=>"134","_destroy"=>"false"},"1"=>{"quantity"=>"5","part_id"=>"168","2"=>{"quantity"=>"","part_id"=>"266","3"=>{"quantity"=>"","part_id"=>"260","4"=>{"quantity"=>"","part_id"=>"262","5"=>{"quantity"=>"","part_id"=>"259","_destroy"=>"false"}}},"commit"=>"Create Product"}
12:58:14 web.1       |    (0.2ms)  begin transaction
12:58:14 web.1       |   ↳ app/controllers/products_controller.rb:29:in `block in create'
12:58:14 web.1       |   Part Load (0.2ms)  SELECT "parts".* FROM "parts" WHERE "parts"."id" = ? LIMIT ?  [["id",134],["LIMIT",1]]
12:58:14 web.1       |   ↳ app/controllers/products_controller.rb:29:in `block in create'
12:58:14 web.1       |   Part Load (0.1ms)  SELECT "parts".* FROM "parts" WHERE "parts"."id" = ? LIMIT ?  [["id",168],266],260],262],259],1]]
12:58:14 web.1       |   ↳ app/controllers/products_controller.rb:29:in `block in create'
12:58:14 web.1       |    (0.2ms)  rollback transaction
12:58:14 web.1       |   ↳ app/controllers/products_controller.rb:29:in `block in create'

我在做什么错呢？：

• 我有两部分可供选择，而不是采用新呈现的形式
• 无法创建产品和products_parts

解决方法

我想通了！:)如果有人会有同样的问题，我将工作代码放在下面。

product.rb

class Product < ApplicationRecord
  has_many :product_parts
  has_many :parts,through: :product_parts
  accepts_nested_attributes_for :parts,reject_if: blank?,allow_destroy: false
  accepts_nested_attributes_for :product_parts,allow_destroy: true
end

product_part.rb

class ProductPart < ApplicationRecord
  belongs_to :part
  belongs_to :product

  accepts_nested_attributes_for :part,reject_if: all_blank
end

part.rb

class Part < ApplicationRecord
  has_many :product_parts
  has_many :products,through: :product_parts
end

products_controller.rb

# GET /products/new
def new
  @product = Product.new
  @product.product_parts.build.build_part
end

products / _form.html.slim

= simple_form_for(@product) do |f|
  = f.error_notification
  = f.error_notification message: f.object.errors[:base].to_sentence if f.object.errors[:base].present?
  = f.input :name,label: false,class: 'form-control',placeholder: t('placeholders.input_product_name')
  fieldset#parts
    = f.simple_fields_for :product_parts do |product_part|
      .field
        == render 'product_part_fields',f: product_part
    = link_to_add_association 'Add part',f,:product_parts,class: 'btn btn-primary btn-xs'
    = f.button :submit 

products / _product_part_fields.html.slim

.nested-fields.field
  .field.has-addons
    = link_to_remove_association f
    .field
      = f.input :quantity
      = f.collection_select :part_id,Part.all,:id,:name,{},{class: 'select2'}

,

服务器日志的末尾表明，您的partial正在寻找一个名为“ part”的变量，并抛出500错误。

将您的_form.html.slim文件更改为：

= simple_form_for(@product) do |f|
  = f.input :name
  = f.simple_fields_for :parts do |part|
    == render 'part_fields',part: part
  = f.button :submit

这会将零件对象发送到零件，并清除错误。

,

fields_for在关联中进行迭代，并为关联中的每个记录执行一次该块，但是如果关联为空，则无需进行任何迭代。

因此，为了显示新记录的输入，您需要在控制器中添加关联种子：

class ProductsController < ApplicationController
  # ...

  # GET /products/new
  def new
    @product = Product.new do |p|
      3.times { p.parts.new } 
    end
  end

  # ...
end 

在您第一次尝试使用该表格时，您还将使用符号:part，该符号将引发NoMethodError (undefined method 'name' for :part:Symbol)。

= f.simple_fields_for :parts do |part|
  = f.label :part.name
  = f.input :part.quantity

它应显示为：

= f.simple_fields_for :parts do |part|
  = f.label part.name
  = f.input part.quantity

@marks的答案将在您第二次尝试时解决丢失的本地地址。