Rails 3-如何重构该控制器代码？

Question

Is there a way to DRY and load objects in a cleaner way (without using before_filter).

Indeed I need @answer and @question in 2 other methods than "show".

Controller :

def show
 @answer = Answer.new pre_form
 @question = Question.find(params[:id])
 @answers = @question.answers.page(params[:page])
 respond_with @question
end

private

def pre_form     
   session[:pre_form][:answer] || session[:pre_form][:question] if session[:pre_form]
end

Thanks in advance

Answer 1

You could just define a method that fetches these for you if so required:

def fetch_question_and_answer(params)
  @answer = Answer.new pre_form
  @question = Question.find(params[:id])
  @answers = @question.answers.page(params[:page])
end

This would roll this up into a simple method call in your various controller methods:

def show
  fetch_question_and_answer(params)
  respond_with @question
end

It can be a little sneaky to go and assign instance variables in methods like this, as that does end up being a little magical in the bad sense, so be careful to label your method clearly to avoid confusion. The alternative is to simply return these and assign them on a case-by-case basis.

I'm not sure why you're opposed to a before_filter method, though, as that's what those are expected to set instance variables so the same rules do not apply.

Answer 2

Similar to above, you can have helper methods that you can use like an instance variable:

helper_method :answer, :question, :answers

def answer
  @answer ||= Answer.new pre_form
end

def question
  @question ||= Question.find(params[:id])
end

def answers
  @answers ||= question.answers.page(params[:page])
end

Since they're helper_methods, you can use them in your views too!

Answer 3

The way you do it is good enough, except from @question.answers.page(params[:page]) that does not follow the law of Demeter and can be written in a better manner.

Instead, you can create a delegate for answers.page so that you can invoke :

@question.answers_page(params[:page])

If you're interested in better design(seems like you are), remember that 2 dots in a Rails statement have a higher probability of being able to be written in a better, more encapsulating manner.

If you find yourself creating new Answer and fetching params all the time, you can keep it DRYer using tadman's proposed method. And, you should consider pushing that method into a module. However, think it through, to see if you really need to do that for DRYer code. Generally speaking, new instances and simplest finders by id tend to be used through controllers.