Rails 3.1限制子模型的数量

Question

大家好，我有两个模型:用户(又名家长)和普罗非(又名子).And，我想限制一个用户的profil数量为一个。

models/user.rb

class User < ActiveRecord::Base

  has_one :profil

end

models/profil.rb

class Profil < ActiveRecord::Base
    attr_accessible :logo
  belongs_to :user
  mount_uploader :logo, ImageUploader


  validate :limit_profil_to_one, :on => :create

    def limit_profil_to_one
      if self.user.profils(:reload).count > 1
         errors.add(:base, "Exceeded thing limit")
      end
  end
end

但是，当我试图创建一个profil时，我会得到以下错误消息：

NoMethodError (undefined method `profils' for nil:NilClass):
  app/models/profil.rb:11:in `limit_profil_to_one'
  app/controllers/profils_controller.rb:52:in `block in create'
  app/controllers/profils_controller.rb:51:in `create  

控制器/轮廓控制器

# -*- encoding : utf-8 -*-

class ProfilsController < ApplicationController


    # GET /factures
  # GET /factures.json
  def index
    @profils = Profil.all

    respond_to do |format|
      format.html # index.html.erb
      format.json { render json: @profil }
    end
  end

  # GET /profils/1
  # GET /profils/1.json
  def show
    @profil = Profil.find(params[:id])

    respond_to do |format|
      format.html # show.html.erb
      format.json { render json: @profil }
    end
  end

  # GET /profils/new
  # GET /profils/new.json
  def new
    @profil = Profil.new

    respond_to do |format|
      format.html # new.html.erb
      format.json { render json: @profil }
    end
  end

  # GET /profils/1/edit
  def edit
    @profil = Profil.find(params[:id])
  end

  # POST /profils
  # POST /profils.json
  def create
    @profil = Profil.new(params[:profil])

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

  # PUT /profils/1
  # PUT /profils/1.json
  def update
    @profil = Profil.find(params[:id])

    respond_to do |format|
      if @profil.update_attributes(params[:profil])
        format.html { redirect_to @profil, notice: 'Profil was successfully updated.' }
        format.json { head :ok }
      else
        format.html { render action: "edit" }
        format.json { render json: @profil.errors, status: :unprocessable_entity }
      end
    end
  end

    # DELETE /factures/1
  # DELETE /factures/1.json
  def destroy
    @profil = Profil.find(params[:id])
    @profil.destroy

    respond_to do |format|
      format.html { redirect_to profils_url }
      format.json { head :ok }
    end
  end
end

我做错什么了？

Answer 1

看看limit_profil_to_one中的第2行-- self.user是0，所以它失败了。

def limit_profil_to_one
    if self.user.profils(:reload).count > 1 # self.user is nil
        errors.add(:base, "Exceeded thing limit")
    end
end

我正在对您的应用程序做一些假设，但在这篇文章中，我将假设您的控制器中有一个当前用户定义在控制器中，并且您正在为该用户创建一个Profil (侧:注意，什么是profil？我假设您实际上是指概要文件)，您应该将控制器中的用户设置为它应该是的用户，如下所示。

def create
    @profil = Profil.new(params[:profil])
    @profil.user = current_user # however you access the currently logged in user

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