rails引用對象nil

Question

我的測驗模型和我的quiz_session模型之間有一對一關聯，當我嘗試訪問測驗控制器中的@quiz.quiz_session時，quiz_session對象爲零。 但是當我在rails控制檯中檢查我的quiz_session對象時，它顯示了一個引用的測驗。

# quizzes_controller.rb: 
def show 
    @quiz_session = @quiz.quiz_session 
    logger.debug "quizzes_controller" 
    logger.debug @quiz_session.inspect 
end 

#development.log output: 
quizzes_controller 
nil 

#quiz.rb: 
class Quiz < ApplicationRecord 
    belongs_to :quiz_session, dependent: :destroy 
    accepts_nested_attributes_for :quiz_session, reject_if: :all_blank, allow_destroy: true 
end 

#quiz_session.rb: 
class QuizSession < ApplicationRecord 
    has_one :quiz 
end 

#rails console: 
irb(main):001:0> QuizSession.first 
    QuizSession Load (0.0ms) SELECT "quiz_sessions".* FROM "quiz_sessions" ORDER BY "quiz_sessions"."id" ASC LIMIT ? [["LIMIT", 1]] 
=> #<QuizSession id: 31, access_key: "srtjki356xm", created_at: "2017-04-23 22:54:51", updated_at: "2017-04-23 22:54:51", quiz_id: 1, current_question_index: nil> 
irb(main):002:0> Quiz.find(1) 
    Quiz Load (0.0ms) SELECT "quizzes".* FROM "quizzes" WHERE "quizzes"."id" = ? LIMIT ? [["id", 1], ["LIMIT", 1]] 
=> #<Quiz id: 1, title: "Chapter 1.1", lecture_unit: "2017-03-19", unlocked_at: "2017-03-19 14:00:00", course_id: 1, created_at: "2017-03-19 02:27:28", updated_at: "2017-03-19 02:27:28"> 

我是Ruby on Rails的新手，並使用Rails 5.0.2。任何幫助，將不勝感激:)

Answer 1

嘗試以下：

# quizzes_controller.rb: 
def show 
    @quiz_session = @quiz.quiz_session 
    logger.debug "quizzes_controller" 
    logger.debug @quiz_session.inspect 
end 

#quiz.rb: 
class Quiz < ApplicationRecord 
    has_one :quiz_session, dependent: :destroy 
    accepts_nested_attributes_for :quiz_session, reject_if: :all_blank, allow_destroy: true 
end 
#quiz_session.rb: 
class QuizSession < ApplicationRecord 
    belongs_to :quiz 
end 

這是因爲你的quiz_session包含quiz_id = 1，但是，這不是一個很好的解決方案，以硬編碼的東西。您應該制定邏輯以通過請求&中的測驗ID，然後動態地創建@quiz = Quiz.find(params[:quiz_id])。目前，您可以使用上述解決方案。