带有has_many，通过和多选的Rails 4嵌套表单

Question

我对嵌套表单和 has_many 关系有疑问。商业案例：有实验室及其供应商。供应商可以在实验室之间共享。

模型

class Lab < ActiveRecord::Base
  has_many :lab_suppliers
  has_many :suppliers, through: :lab_suppliers
  accepts_nested_attributes_for :lab_suppliers
end

class Supplier < ActiveRecord::Base
  has_many :lab_suppliers
  has_many :labs, through: :lab_suppliers
  accepts_nested_attributes_for :lab_suppliers
end

class LabSupplier < ActiveRecord::Base
  belongs_to :lab
  belongs_to :supplier

  accepts_nested_attributes_for :lab
  accepts_nested_attributes_for :supplier
end

表格

<%= form_for(@lab) do |f| %>
  <div class="field">
    <%= f.label :code %><br>
    <%= f.text_field :code %>
  </div>
  <div class="field">
    <%= f.label :name %><br>
    <%= f.text_field :name %>
  </div>
  <div class"field">
    <%= fields_for :lab_suppliers do |ff| %>
      <%= ff.label :supplier_id %><br>
      <%= ff.collection_select :supplier_id, Supplier.all, :id, :name,  {include_blank: true}, {:multiple => true, :class=>""} %> 
    <% end %>
  </div>
  <div class="actions">
    <%= f.submit %>
  </div>
<% end %>

控制器

class LabsController < ApplicationController
  before_action :set_lab, only: [:show, :edit, :update, :destroy]

  # GET /labs/new
  def new
    @lab = Lab.new
    @lab.lab_suppliers.build
  end

  # POST /labs
  # POST /labs.json
  def create
    #raise params.inspect

    @lab = Lab.new(lab_params)

    @lab_supplier = @lab.lab_suppliers.new(params[:lab_suppliers])
    @lab_supplier.save
    @lab.save


    private

    def lab_params
      params.require(:lab).permit(:code, :name, lab_suppliers_attributes: [])
    end
end

提交表单后对参数的检查结果：

参数：

{"utf8"=>"✓",
 "authenticity_token"=>"...",
 "lab"=>{"code"=>"L01",
 "name"=>"xxx"},
 "lab_suppliers"=>{"supplier_id"=>["",
 "1",
 "3"]},
 "commit"=>"Create Lab"}

提交表单时，我收到 ActiveModel::ForbiddenAttributesError 上线：

@lab_supplier = @lab.lab_suppliers.new(params[:lab_suppliers])

为了让它按预期工作，我缺少什么？

Answer 1

您似乎需要明确告诉lab_params 您需要传递lab_suppliers 中的哪些属性，例如：

params.require(:lab).permit(:code, :name, lab_suppliers_attributes: [:supplier_id])

试试看，然后告诉我。

Answer 2

链接到帮助我找到工作解决方案的其他帖子： [Rails nested form with multiple entries

下面我提供了工作解决方案，展示了如何将多选中的值作为嵌套属性传递并将它们插入到数据库中。

模型

class Lab < ActiveRecord::Base
   has_many :lab_suppliers#, :foreign_key => 'lab_id', dependent: :destroy
   has_many :suppliers, through: :lab_suppliers
   accepts_nested_attributes_for :lab_suppliers, :allow_destroy => true
end

class Supplier < ActiveRecord::Base
  has_many :lab_suppliers
  has_many :labs, through: :lab_suppliers
end

class LabSupplier < ActiveRecord::Base
  belongs_to :lab
  belongs_to :supplier
end

评论： accept_nested_attributes_for 仅放在 has_many/has_one 一侧。不需要放在belongs_to一侧

表格（实验室）

<%= form_for(@lab) do |f| %>
  <div class="field">
    <%= f.label :code %><br>
    <%= f.text_field :code %>
  </div>
  <div class="field">
    <%= f.label :name %><br>
    <%= f.text_field :name %>
  </div>
    <div class"field">
<%= f.fields_for :lab_suppliers do |ff| %>
  <%= ff.label :supplier_id %><br>
  <%= ff.collection_select :supplier_id, Supplier.all, :id, :name,  {include_blank: true}, {:multiple => true, :class=>""} %>
<% end %>

控制器

评论： 无需在供应商或 lab_suppliers 控制器中允许任何其他参数

class LabsController < ApplicationController
  before_action :set_lab, only: [:show, :edit, :update, :destroy]

def new
  @lab = Lab.new
  @lab.lab_suppliers.build
end


def create
   @lab = Lab.new(lab_params)

@startcount=1   #start counting from 1 because the first element in the array of nested params is always null
@lab.lab_suppliers.each do |m|
  #raise lab_params[:lab_suppliers_attributes]["0"][:supplier_id][@startcount].inspect
  m.supplier_id = lab_params[:lab_suppliers_attributes]["0"][:supplier_id][@startcount]
  @startcount +=1
end 

respond_to do |format|
  if @lab.save
    lab_params[:lab_suppliers_attributes]["0"][:supplier_id].drop(@startcount).each do |m|
      @lab.lab_suppliers.build(:supplier_id => lab_params[:lab_suppliers_attributes]["0"][:supplier_id][@startcount]).save
      @startcount += 1
    end
    format.html { redirect_to labs_path, notice: 'Lab was successfully created.' }
    format.json { render :show, status: :created, location: @lab }
  else
    format.html { render :new }
    format.json { render json: @lab.errors, status: :unprocessable_entity }
  end
end
end


    private

def lab_params
  params.require(:lab).permit(:name, :code, lab_suppliers_attributes: [supplier_id: [] ])
end
end

注释：lab_suppliers_attributes 中的supplier_id: [] 允许传递来自多个下拉列表的值数组