Ruby on Rails的使用模特協會

Question

我有rails_best_practices寶石和我得到以下警告：

APP/app/controllers/users_controller.rb - use model association (for @user_answer)

參考這個要點的代碼：

begin 
    @user_answer = @user.user_answers.where(:question_id => @question_id).first 
    if @user_answer 
    @user_answer.answer_id = @answer_id 
    @user_answer.save! 
    @message = 'Answer updated successfully!' 
    else 
    @user.user_answers.create(:question_id => params[:questionId], :answer_id => params[:answerId]) 
    @message = 'Answer submitted successfully!' 
    end 
rescue ex 
    @message = ex.message.split(':')[1].chomp 
end 

但根據page on model association它看起來不像是違反了這一點，它看起來像是正確的。我是否錯過了這件事？

Answer 1

問題在於直接訪問變量在@user_answer對象，並且@user變量中不更新user_answer ...既然Rails有一個update方法，我們可以做到這一點，像這樣：

begin 
    @user_answer = @user.user_answers.where(:question_id => @question_id).first 
    if @user_answer 
    @user.user_answers.update(:question_id => @question_id, :answer_id => @answer_id) 
    @message = 'Answer updated successfully!' 
    else 
    @user.user_answers.create(:question_id => @question_id, :answer_id => @answer_id) 
    @message = 'Answer submitted successfully!' 
    end 
rescue ex 
    @message = ex.message.split(':')[1].chomp 
end 

但我們可以做得更好。與創建和更新不同，我們可以簡單地使用Ruby的短路評估來創建@user_answer符號並更新它，無論它是否是新的。

begin 
    @user_answer = @user.user_answers.where(:question_id => @question_id).first || @user.user_answers.new 
    @user_answer.update_attributes!(question_id: @question_id, answer_id: @answer_id) 
    @message = 'Answer submitted successfully!' 
rescue ex 
    @message = ex.message.split(':')[1].chomp 
end