Ruby on Rails，關聯兩個實例的正確方法是什麼？

Question

我是學習Rails 3和通過Q &應用教程的新手。我只是想知道爲什麼我不能在一個問題的特定答案中做到這一點（我得到一個錯誤）。它適用於當前用戶...

class AnswersController < ApplicationController 

before_filter :auth, only: [:create] 

def create 
    @question = Question.find(params[:question_id]) 
    **@answer = Answer.new(params[:answer]) 
    @answer.question = @question 
    @answer.user = current_user** 
    if @answer.save 
     flash[:success] = 'Your answer has been posted!' 
     redirect_to @question 
    else 
     @question = Question.find(params[:question_id]) 
     render 'questions/show' 
    end 
end 
end 

的教程說，這是正確的做法：

class AnswersController < ApplicationController 

before_filter :auth, only: [:create] 

def create 
    @question = Question.find(params[:question_id]) 
    **@answer = @question.answers.build(params[:answer])** 
    @answer.user = current_user 
    if @answer.save 
     flash[:success] = 'Your answer has been posted!' 
     redirect_to @question 
    else 
     @question = Question.find(params[:question_id]) 
     render 'questions/show' 
    end 
end 
end 

Answer 1

做以下

@answer = @question.answers.build(params[:answer) 

相同這樣

@answer = Answer.new(params[:answer]) 
@answer.question_id = @question.id 

做一個build將關係屬性添加到新答案，在這種情況下，question_id

至於錯誤，您能否提供您收到的錯誤類型？