“ 1條禁止保存的錯誤：用戶不能空白”-Hartl Ruby on Rails教程

Question

我將遵循Hartl Rails教程，到目前為止，已經創建了2個模型：“用戶”模型和“列表”模型（本質上是教程中的“ Microposts”模型，但自定義為更多Craigslist） -類型的帖子/廣告，而不是Twitter類型的狀態更新）。

我設置了帶有“ belongs_to：user ”的“ listing.rb ”模型，還設置了帶有“ has_many：listings，dependent：destroy ”的“ user.rb ”模型，甚至為“ listings”提供了一個user_id索引和created_at索引 。

但是，每當我嘗試創建一個新清單並提交它時，都會出現以下錯誤：

“ 1個錯誤，禁止保存此列表：用戶不能為空”。

沒有其他錯誤出現，這使我假設所需的其他“列表”列（名稱，描述，價格和可選圖像）都可以，但是由於某種原因User_id沒有附加到創建的清單中？

會有什么原因呢？

這是我的user.rb，listing.rb和schema.rb（如果有幫助的話）以及控制器：

schema.rb ：

ActiveRecord::Schema.define(version: 20150223175136) do

  create_table "categories", force: true do |t|
    t.string   "name"
    t.datetime "created_at"
    t.datetime "updated_at"
  end

  create_table "listings", force: true do |t|
    t.string   "name"
    t.text     "description"
    t.decimal  "price"
    t.datetime "created_at",  null: false
    t.datetime "updated_at",  null: false
    t.string   "image"
    t.integer  "user_id"
    t.integer  "category_id"
    t.string   "username"
  end

  add_index "listings", ["user_id", "created_at"], name:     "index_listings_on_user_id_and_created_at"
  add_index "listings", ["user_id"], name: "index_listings_on_user_id"
  add_index "listings", ["username"], name: "index_listings_on_username"

  create_table "users", force: true do |t|
    t.string   "email"
    t.datetime "created_at",                        null: false
    t.datetime "updated_at",                        null: false
    t.string   "password_digest"
    t.string   "remember_digest"
    t.boolean  "admin",             default: false
    t.string   "activation_digest"
    t.boolean  "activated",         default: false
    t.datetime "activated_at"
    t.string   "reset_digest"
    t.datetime "reset_sent_at"
    t.string   "username"
    t.string   "first_name"
    t.string   "last_name"
  end

  add_index "users", ["email"], name: "index_users_on_email", unique: true

end

user.rb ：

class User < ActiveRecord::Base
    has_many :listings, dependent: :destroy
    attr_accessor :remember_token, :activation_token, :reset_token
    before_save   :downcase_email
    before_create :create_activation_digest
    validates :first_name,  presence: true, length: { maximum: 25 }
    validates :last_name, presence: true, length: { maximum: 50 }
    validates :username, presence: true, uniqueness: true, length: {maximum: 50 }
    VALID_EMAIL_REGEX = /\A[\w+\-.]+@[a-z\d\-]+(\.[a-z\d\-]+)*\.[a-z]+\z/i
    validates :email, presence: true, length: { maximum: 255 },
                                        format: { with: VALID_EMAIL_REGEX },
                                        uniqueness: { case_sensitive: false }
    has_secure_password
    validates :password, length: { minimum: 6 }, allow_blank: true


    class << self
        # Returns the hash digest of the given string.
        def digest(string)
            cost = ActiveModel::SecurePassword.min_cost ? BCrypt::Engine::MIN_COST :
                                                                                                        BCrypt::Engine.cost
            BCrypt::Password.create(string, cost: cost)
        end

        # Returns a random token.
      def new_token
        SecureRandom.urlsafe_base64
      end
    end

    # Remembers a user in the database for use in persistent sessions.
  def remember
    self.remember_token = User.new_token
    update_attribute(:remember_digest, User.digest(remember_token))
  end

    # Returns true if the given token matches the digest.
  def authenticated?(attribute, token)
    digest = send("#{attribute}_digest")
    return false if digest.nil?
    BCrypt::Password.new(digest).is_password?(token)
  end

  # Forgets a user.
  def forget
    update_attribute(:remember_digest, nil)
  end

  # Activates an account.
  def activate
    update_attribute(:activated,  true)
    update_attribute(:activated_at, Time.zone.now)
  end

  # Sends activation email.
  def send_activation_email
    UserMailer.account_activation(self).deliver_now
  end

  # Sets the password reset attributes.
  def create_reset_digest
    self.reset_token = User.new_token
    update_attribute(:reset_digest, User.digest(reset_token))
    update_attribute(:reset_sent_at, Time.zone.now)
  end

  # Sends password reset email.
  def send_password_reset_email
    UserMailer.password_reset(self).deliver_now
  end

  # Returns true if a password reset has expired.
  def password_reset_expired?
    reset_sent_at < 2.hours.ago
  end


  private

    # Converts email to all lower-case.
    def downcase_email
        self.email = email.downcase
    end

    # Creates and assigns the activation token and digest.
    def create_activation_digest
        self.activation_token  = User.new_token
        self.activation_digest = User.digest(activation_token)
    end
end

listing.rb ：

class Listing < ActiveRecord::Base
  belongs_to :user
  default_scope -> { order('created_at DESC') }
  validates :name, presence: true
  validates :description, presence: true
  validates :price, presence: true
  validates :user_id, presence: true
  mount_uploader :image, ImageUploader
end

這是“ Listings ”控制器：

class ListingsController < ApplicationController
  before_action :logged_in_user, only: [:create, :destroy]
  before_action :correct_user,   only: :destroy

  def index
    @listings = Listing.all
  end

  def show
  end

  def new
    @listing = Listing.new
  end

  def edit
  end

  def create
  @listing = Listing.new(listing_params)
    if @listing.save
      redirect_to @listing
      flash[:success] = "Listing was successfully created."
    else
      render 'new'
    end
  end

  def update
    if @listing.update(listing_params)
      flash[:success] = "Listing was successfully updated."
      redirect_to @listing
    else
      render 'edit'
    end
  end

  def destroy
    @listing.destroy
    flash[:success] = "Listing deleted."
    redirect_to request.referrer || root_url
  end

  private

    def listing_params
      params.require(:listing).permit(:name, :description, :price, :image)
    end

    def correct_user
      @listing = current_user.listings.find_by(id: params[:id])
      redirect_to root_url if @listing.nil?
    end
end

和“用戶”控制器：

class UsersController < ApplicationController
  before_action :logged_in_user, only: [:index, :edit, :update, :destroy]
  before_action :correct_user,   only: [:edit, :update]
  before_action :admin_user,     only: :destroy

  def show
    @user = User.find(params[:id])
  end

  def index
    @users = User.paginate(page: params[:page])
  end

  def new
    @user = User.new
  end

  def create
    @user = User.new(user_params)
    if @user.save
      @user.send_activation_email
      flash[:info] = "Please check your email to activate your account."
      redirect_to root_url
    else
      render 'new'
    end
  end

  def edit
    @user = User.find(params[:id])
  end

  def update
    @user = User.find(params[:id])
    if @user.update_attributes(user_params)
      flash[:success] = "Profile updated"
      redirect_to @user
    else
      render 'edit'
    end
  end

  def destroy
    User.find(params[:id]).destroy
    flash[:success] = "User deleted"
    redirect_to users_url
  end


  private

    def user_params
      params.require(:user).permit(:first_name, :last_name, :username, :email, 
                                   :password, :password_confirmation)
    end

    # Before filters

    # Confirms the correct user.
    def correct_user
      @user = User.find(params[:id])
      redirect_to(root_url) unless current_user?(@user)
    end

    # Confirms an admin user.
    def admin_user
      redirect_to(root_url) unless current_user.admin?
    end
end

Answer 1

我不熟悉您所遵循的教程，但是用戶不會自動附加到新創建的清單中，您需要明確地執行此操作。 在ListingsController的create操作中，將第一行替換為以下內容：

@listing = current_user.listings.build(listing_params)

在這種情況下， Listing通過listings關聯建立（尚未保存），並且current_user自動設置為user 。 您可以執行以下操作：

@listing = Listing.new(listing_params)
@listing.user = current_user

但更喜歡較短的版本。