Question

我正在创建一个项目，但每当我尝试create grade Class student使用current_user.grade.create()或current_user.create_grade()获取错误时“未定义的方法为nil类创建”

我的代码如下。

Student.rb

class Student < User

  has_one :user_grade , dependent: :destroy, foreign_key: 'user_id'
  has_one :grade , through: :user_grade

end

Grade.rb

class Grade < ApplicationRecord

  has_many :user_grades, dependent: :destroy
  has_many :admins, through: :user_grades

  has_many :teachers, through: :user_grades

  has_many :students , through: :user_grades

  has_many :guardians, through: :user_grades

  has_many :posts, dependent: :destroy

  validates_presence_of :cls

end

user_grade.rb

class UserGrade < ApplicationRecord

  belongs_to :grade
  belongs_to :admin, optional: true, class_name: 'Admin', foreign_key: 'user_id'
  belongs_to :teacher, optional: true, class_name: 'Teacher', foreign_key: 'user_id'
  belongs_to :student, optional: true, class_name: 'Student', foreign_key: 'user_id'
  belongs_to :guardian, optional: true, class_name: 'Guardian', foreign_key: 'user_id'


end

Answer 1

尝试使用current_user.grade = Grade.new({})。然后调用current_user.save将保存关联并保存新的Grade。

nil的未定义方法`create'：NilClass

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