Rails 多态关联不会保存 _type

Question

我的项目中有几个模型：Request、Work、Car 和 Employee。 Work 是 Request 和 Car/Employee 之间的中间模型。

以下是协会：

请求

has_many :works, dependent: :destroy
def performers
  works.map {|x| x.performer}
end

工作

belongs_to :request
belongs_to :performer, polymorphic: true

汽车

has_many :works, as: :performer
has_many :requests, through: :works, as: :performer

员工

has_many :works, as: :performer
has_many :requests, through: :works, as: :performer

查看用于创作作品：

<%= form_for([@request, @work]) do |f| %>
    <%= (f.collection_select :performer_id, Employee.all, :id, :name) if @request.type == "StaffRequest" %>
    <%= (f.collection_select :performer_id, Car.all, :id, :select_info) if @request.type == "CarRequest" %>
    <%= f.submit 'OK' %>
<% end %>

工作控制器

  def new
    @work = @request.works.new
  end

  def create
    @work = @request.works.new(work_params)
  end

  def work_params
      params.require(:work).permit(:performer_id, :request_id)
  end

问题是我的 performer_type 列总是空的，它没有保存 class 名称。可能是什么问题？有什么想法吗？

Answer 1

因为你没有通过它是空的，你应该为你的表单添加一个隐藏字段：

<%= form_for([@request, @work]) do |f| %>
  <% if @request.type == "StaffRequest" %>
    <%= (f.hidden_field :performer_type, value: "Employee")  %>
    <%= (f.collection_select :performer_id, Employee.all, :id, :name)  %>
  <% elsif @request.type == "CarRequest" %>
    <%= (f.hidden_field :performer_type, value: "Car") %>
    <%= (f.collection_select :performer_id, Car.all, :id, :select_info) %>
  <% end %>
    <%= f.submit 'OK' %>
<% end %>

Answer 2

除了 :performer_id，您还必须传递 :performer_type，一种方法是通过 select_tag :

形式

def create 
  @work = @request.works.new(work_params)
end

def work_params
  # use :performer if you use :performer as in the select form field
  params.require(:work).permit(:performer, :request_id)

  # OR

  # use :performer_id & :performer_type if you also use the hidden field
  params.require(:work).permit(:performer_id, :performer_type, :request_id)
end

有一个很好的例子（对于 Rails 4.2）使用单个 select 表单字段进行多态，所以你可以这样写：

<%= f.grouped_collection_select :global_performer, [ Car, Employee ], :all, :model_name, :to_global_id, :name %>

How to create grouped select box in Rails for polymorphic association using Global ID?

Rails 多态关联不会保存 _type

Rails polymorphic association won't save _type

ruby-on-rails

polymorphic-associations