Rails 3.1 limit the number of child models

Question

Hello guys I've 2 models: User(aka parent) and Profil(aka child).And I want to limit the number of profil for a user to one.

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

But when I try to create a profil I get the following error message:

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  

controllers/profils_controller.rb

# -*- 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

What I am doing wrong?

Answer 1

Look at line 2 in the limit_profil_to_one - self.user is nil so it is failing.

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

I am making some assumptions about what your app is doing, but for this post I am going to assume that your controller has a current user defined in the controller and that you are creating a Profil for that User (side: note, what is a profil? I am assuming you actually mean profile) You should set the user in the controller to the user it is supposed to be, like so.

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