带有 has_many through 和 join 表的简单表格答案

【问题标题】：Simple form with has_many through and join table带有 has_many through 和 join 表的简单表格
【发布时间】：2020-08-24 13:50:14
【问题描述】：

我有模型：Product、Parts 和 ProductParts

产品.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

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

我有连接表：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
选择零件（从所有零件中）并定义每个零件的数量

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

但它不渲染任何东西。你有什么正确的方法吗？

我也尝试过这样做：

_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       |   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       |   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       |   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       |   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       |   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       |   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       |   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       |   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       |   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       |   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       |   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       |   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       |   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       |   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       |   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       |   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       |   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       |   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，我几乎就在我想去的地方:) 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

呈现表单时，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。它看起来像这样： screenshot of rendered form

产品未创建，重新加载表单后，我总是有 2 个部分的字段。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", "_destroy"=>"false"}, "2"=>{"quantity"=>"", "part_id"=>"266", "_destroy"=>"false"}, "3"=>{"quantity"=>"", "part_id"=>"260", "_destroy"=>"false"}, "4"=>{"quantity"=>"", "part_id"=>"262", "_destroy"=>"false"}, "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], ["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", 266], ["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", 260], ["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", 262], ["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", 259], ["LIMIT", 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'

我做错了什么？：

我有两个部分可供选择，而不是新呈现形式的一个
无法创建产品和 products_parts

【问题讨论】：

你能告诉我们你在哪里渲染局部吗？检查您的服务器日志，它实际上正在呈现，它列出了它在输出中呈现的模板/部分
我已经根据您的提问更新了问题

标签： ruby-on-rails join nested-attributes has-many-through cocoon-gem

【解决方案1】：

我想通了！:) 如果有人遇到同样的问题，我将工作代码放在下面。

产品.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

产品/_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

产品/_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'}

【讨论】：

【解决方案2】：

您的服务器日志的末尾显示您的部分正在寻找一个名为“部分”的变量，并引发 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part对象发送到partial，并清除错误。

【讨论】：

谢谢你标记它解决了服务器错误的问题并呈现了表单，但我仍然没有机会从 db 的部件列表中选择部件以与新产品同时添加到它们。

【解决方案3】：

fields_for 遍历关联并为关联中的每条记录执行一次块，但如果关联为空，则没有可迭代的内容。

因此，为了显示新记录的输入，您需要在控制器中播种关联：

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符号:part 的表单时，这将引发NoMethodError (undefined method 'name' for :part:Symbol)。

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

应该是：

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

@marks 回答在您的第二次尝试中解决了缺失的本地问题。

【讨论】：