RAILS:嵌套模型和回调中nil:NilClass的未定义方法‘`profile’

Question

这是一个实际的工作示例，我在上一篇文章中根据两位成员的要求对其进行了分解和简化，其中包含了更多细节。我提取并重写了这些代码，以解决持续两天的问题: nil:NilChass的未定义方法“配置文件”。

我使用gem "faker“和SQLite数据库浏览器，省略了控制器和视图，并专注于建模问题。

最初的问题出现在Goal.rb中，错误消息为："undefined method‘`profile’for nil:NilClass“。根据SQLite DB Browser，已成功创建用户和配置文件记录。

问题出在Goal.rb模型下的一行"user.profile.lbm_lbs“。我不太明白为什么user.profile不存在，尽管user.profile是通过admin.profile =Profile.create！(名称...)创建的。填充(gem faker)应用包exec rake db: sample_data.rake

我之前发布的链接：RAILS: How to make new collection.build in a callback?

BffmModel::Application.routes.draw do
  resources :users do
    resource :profile
    resource :goal
    resource :tdee
    resources :progress_charts
  end
end

# == Schema Information
#
# Table name: users
#
#  id              :integer         not null, primary key
#  email           :string(255)
#  password_digest :string(255)
#  created_at      :datetime        not null
#  updated_at      :datetime        not null
#  remember_token  :string(255)
#

class User < ActiveRecord::Base
    attr_accessible :email, :email_confirmation, :password, :password_confirmation

    has_secure_password
    has_one :profile
    has_one :goal
    has_one :tdee
    has_many :progress_charts

    before_save { |user| user.email = email.downcase }
    before_save :create_remember_token

    VALID_EMAIL_REGEX = /\A[\w+\-.]+@[a-z\d\-.]+\.[a-z]+\z/i

    validates :email, :confirmation => true, :presence => true, 
                        length: { maximum: 50 },
                        format: { with: VALID_EMAIL_REGEX },
                        uniqueness: { case_sensitive: false }

    validates :email_confirmation, :presence => true
    validates :password, length: { minimum: 6 }
    validates :password_confirmation, presence: true

    private

        def create_remember_token
            self.remember_token = SecureRandom.urlsafe_base64
        end
end

# == Schema Information
#
# Table name: profiles
#
#  id               :integer         not null, primary key
#  name             :string(255)
#  surname          :string(255)
#  gender           :string(255)
#  date_of_birth    :date
#  body_weight_lbs  :integer
#  height_in_feets  :integer
#  height_in_inches :integer
#  bf_pct           :decimal(5, 2)
#  bf_lbs           :decimal(5, 2)
#  lbm_lbs          :decimal(5, 2)
#  user_id          :integer
#  created_at       :datetime        not null
#  updated_at       :datetime        not null
#

class Profile < ActiveRecord::Base
    attr_accessible :name, :surname, :gender, :date_of_birth, :body_weight_lbs,
                    :bf_pct, :height_in_feets, :height_in_inches
    belongs_to :user

    before_save :set_gender
    before_save :calculate_body_fat_lbs
    before_save :calculate_lean_body_mass_lbs

    private

        def set_gender
            if self.gender == "1"
                self.gender = "Male"
            elsif self.gender == "2"
                self.gender = "Female"
            end
        end

        def calculate_body_fat_lbs
            self.bf_lbs = ( self.bf_pct / 100 ) * self.body_weight_lbs
            self.bf_lbs = self.bf_lbs.round(0)
        end

        def calculate_lean_body_mass_lbs
            self.lbm_lbs = self.body_weight_lbs - self.bf_lbs
        end
end

# == Schema Information
#
# Table name: goals
#
#  id                    :integer         not null, primary key
#  desired_bf_pct        :decimal(, )
#  goal_type             :string(255)
#  ideal_body_weight_lbs :decimal(5, 2)
#  ideal_bfm_lbs         :decimal(5, 2)
#  fat_to_lose_lbs       :decimal(5, 2)
#  lbm_to_gain_lbs       :decimal(5, 2)
#  user_id               :integer
#  created_at            :datetime        not null
#  updated_at            :datetime        not null
#

class Goal < ActiveRecord::Base
  attr_accessible :desired_bf_pct, :goal_type

  belongs_to :user

  before_save :set_goal
  before_save :calculate_ideal_body_weight_lbs

  private

    def set_goal
      if self.goal_type == "1"
        self.goal_type = "Lose Fat"
      elsif self.goal_type == "2"
        self.goal_type = "Gain Muscles"
      end
    end

    def calculate_ideal_body_weight_lbs

      self.ideal_body_weight_lbs = user.profile.lbm_lbs / ( 1 - ( self.desired_bf_pct / 100 ) )
      self.ideal_body_weight_lbs = self.ideal_body_weight_lbs.round(0)
    end
end

/lib/task/sample_data.rake作为测试数据

namespace :db do
  desc "Fill database with sample data"
  task populate: :environment do
    admin = User.create!(email: "mikey@example.com",
                         email_confirmation: "mikey@example.com",
                         password: "foobar",
                         password_confirmation: "foobar")

    admin.profile = Profile.create!(name: "Michael",
                                    surname: "Colins",
                                    gender: "Male",
                                    date_of_birth: "1975-03-05",
                                    body_weight_lbs: 200,
                                    bf_pct: 25.5,
                                    height_in_feets: 5,
                                    height_in_inches: 11 )

    admin.goal = Goal.create!(  desired_bf_pct: 12,
                                goal_type: "Lose Fat")

    admin.tdee = Tdee.create!( tdee_calc_type: "Harris-Benedict",
                  activity_lvl: "BMR x 1.2")
  end
end

谢谢。

Answer 1

admin.goal = Goal.create!(  desired_bf_pct: 12,
                            goal_type: "Lose Fat")

这条线快把你给绊倒了。

Goal.create!(  desired_bf_pct: 12,
               goal_type: "Lose Fat")

此部分将创建一个新的Goal。在此步骤中，不设置:user关系。这意味着Goal中的user方法将返回nil。因为nil没有profile方法，所以不能在保存user.profile之前从calculate_ideal_body_weight_lbs方法中调用Goal。使用已有的代码，您必须显式设置:user关系。

Goal.create!(  desired_bf_pct: 12,
               goal_type: "Lose Fat",
               user: admin )

Answer 2

显然，user是零。你的问题让人觉得你不知道这一点。可能您没有登录，或者您不了解user方法的作用。