设计多态协会：如何解决“用户必须荟萃存在”错误

Question

我在一个Rails 5项目中，我使用的设备如下创建使用多态关系的多个模型工作：

class DeviseCreateUsers < ActiveRecord::Migration[5.0] 
    def change 
    create_table :users do |t| 

     t.string :meta_type 
     t.integer :meta_id 

     ## Database authenticatable 
     t.string :email,    null: false, default: "" 
     t.string :encrypted_password, null: false, default: "" 

     ## Recoverable 
     t.string :reset_password_token 
     t.datetime :reset_password_sent_at 

     ## Rememberable 
     t.datetime :remember_created_at 

     ## Trackable 
     t.integer :sign_in_count, default: 0, null: false 
     t.datetime :current_sign_in_at 
     t.datetime :last_sign_in_at 
     t.string :current_sign_in_ip 
     t.string :last_sign_in_ip 

     ## Confirmable 
     # t.string :confirmation_token 
     # t.datetime :confirmed_at 
     # t.datetime :confirmation_sent_at 
     # t.string :unconfirmed_email # Only if using reconfirmable 

     ## Lockable 
     # t.integer :failed_attempts, default: 0, null: false # Only if lock strategy is :failed_attempts 
     # t.string :unlock_token # Only if unlock strategy is :email or :both 
     # t.datetime :locked_at 


     t.timestamps null: false 
    end 

    add_index :users, :email,    unique: true 
    add_index :users, :reset_password_token, unique: true 
    add_index :users, :meta_id 
    add_index :users, :meta_type 
    # add_index :users, :confirmation_token, unique: true 
    # add_index :users, :unlock_token,   unique: true 
    end 
end 

user.rb

class User < ApplicationRecord 
    # Include default devise modules. Others available are: 
    # :confirmable, :lockable, :timeoutable and :omniauthable 
    devise :database_authenticatable, :registerable, 
     :recoverable, :rememberable, :trackable, :validatable 

    belongs_to :meta, polymorphic: true 
end 

我有一个类保姆（我会添加后的具体护理人员字段）

class CreateCaregivers < ActiveRecord::Migration[5.0] 
    def change 
    create_table :caregivers do |t| 

     t.timestamps 
    end 
    end 
end 

caregiver.rb

class Caregiver < ApplicationRecord 
    has_one :user, as: :meta, dependent: :destroy 
    accepts_nested_attributes_for :user 
end 

我已经为护理员班级搭建了控制器。以下是文件：

class CaregiversController < ApplicationController 
    before_action :set_caregiver, only: [:show, :edit, :update, :destroy] 

    # GET /caregivers 
    # GET /caregivers.json 
    def index 
    @caregivers = Caregiver.all 
    end 

    # GET /caregivers/1 
    # GET /caregivers/1.json 
    def show 
    end 

    # GET /caregivers/new 
    def new 
    @caregiver = Caregiver.new 
    @caregiver.build_user 
    end 

    # GET /caregivers/1/edit 
    def edit 
    end 

    # POST /caregivers 
    # POST /caregivers.json 
    def create 
    @caregiver = Caregiver.new(caregiver_params) 

    respond_to do |format| 
     if @caregiver.save 
     format.html { redirect_to @caregiver, notice: 'Caregiver was successfully created.' } 
     format.json { render :show, status: :created, location: @caregiver } 
     else 
     format.html { render :new } 
     format.json { render json: @caregiver.errors, status: :unprocessable_entity } 
     end 
    end 
    end 

    # PATCH/PUT /caregivers/1 
    # PATCH/PUT /caregivers/1.json 
    def update 
    respond_to do |format| 
     if @caregiver.update(caregiver_params) 
     format.html { redirect_to @caregiver, notice: 'Caregiver was successfully updated.' } 
     format.json { render :show, status: :ok, location: @caregiver } 
     else 
     format.html { render :edit } 
     format.json { render json: @caregiver.errors, status: :unprocessable_entity } 
     end 
    end 
    end 

    # DELETE /caregivers/1 
    # DELETE /caregivers/1.json 
    def destroy 
    @caregiver.destroy 
    respond_to do |format| 
     format.html { redirect_to caregivers_url, notice: 'Caregiver was successfully destroyed.' } 
     format.json { head :no_content } 
    end 
    end 

    private 
    # Use callbacks to share common setup or constraints between actions. 
    def set_caregiver 
     @caregiver = Caregiver.find(params[:id]) 
    end 

    # Never trust parameters from the scary internet, only allow the white list through. 
    def caregiver_params 
     params.require(:caregiver).permit(user_attributes: [ :id, :email, :password, :password_confirmation ]) 
    end 
end 

这里是创建表单

<%= form_for(@caregiver) do |f| %> 
    <% if @caregiver.errors.any? %> 
    <div id="error_explanation"> 
     <h2><%= pluralize(@caregiver.errors.count, "error") %> prohibited this caregiver from being saved:</h2> 

     <ul> 
     <% caregiver.errors.full_messages.each do |message| %> 
     <li><%= message %></li> 
     <% end %> 
     </ul> 
    </div> 
    <% end %> 

    <%= f.fields_for :user do |u| %> 
    <div class="col-lg-6"> 
    <%= u.label :email %><br> 
    <%= u.text_field :email %> 
    </div> 

    <div class="col-lg-6"> 
    <%= u.label :password %><br> 
    <%= u.text_field :password %> 
    </div> 

    <div class="col-lg-6"> 
    <%= u.label :password_confirmation %><br> 
    <%= u.text_field :password_confirmation %> 
    </div> 
    <% end %> 


    <div class="actions"> 
    <%= f.submit %> 
    </div> 
<% end %> 

我下面this例子。

Github上的示例工作正常。然而，当我尝试创建一个新的纪录照顾者，我收到以下错误：

User meta must exist

我无法找到是什么错误。

Answer 1

导轨5使得默认情况下需要关联belongs_to。要禁用它，您需要将optional: true添加到belongs_to

belongs_to :meta, polymorphic: true, optional: true