Model has_many 3 degrees separation

rubyonrails-talk
1

I feel like this should be simple but it's stumping me.

In the following model, is there an easy way to setup my models so that I can make the following call: @company.survey_answers

class Company < ActiveRecord::Base   has_many :surveys   has_many :survey_questions, :through => :surveys end

class Surveys ...   belongs_to :company   has_many :survey_questions end

class SurveyQuestions ...   belongs_to :survey   has_many :survey_answers end

class SurveyAnswers ...   belongs_to :survey_question end

Thanks in advance for any help.

Cheers, Chad

2

What happens when you try:

(1) @company.surveys.survey_questions.survey_answers

or

(2) @company.survey_questions.survey_answers

I believe form (1) should certainly work after removing the line 'has_many :survey_questions, :through => :surveys'

I am uncertain if form (2) will work (because I am uncertain if has_many :through works that way and no time to test it here)

I don't see how '@company.survey_answers' could work since there is no has_many relationship with the name 'survey_answers' in the Company class. It is only defined in the SurveyQuestions class.

HTH,

Peter

3

I like the idea, but this is what I get:

@answers = @company.surveys.survey_questions.survey_answers

undefined method `survey_questions' for #<Class:0x203b590>

I feel like the first call, @company.surveys is just returning an array and then I'm trying to call the survey_questions method on that array.

Is there a way to modify that call to get the desired chaining?

4

As you say @company.surveys returns an array of Surveys, so normally you would have to say @company.surveys[i].survey_questions which will again return an array of questions, and so on. Are you asking for a means to automatically combine all the results obtained by iterating each of the arrays down the chain? I don’t know of a way to do that automatically, without iterating each of the arrays and building a combined list. I would not be in the least surprised to find that Ruby has some magic construct to achieve this however. Maybe this is a challenge to the Ruby geeks to provide the answer by the most concise (and possibly undecipherable) code.

5

Ya I agree with you - I can manually combine arrays no problem, but then it's a pain to sort and I'm unable to use named_scope's, etc.

There's got to be a clean way...

6

OK, that was stupid of me to post without testing first.

Sorry for the noise it created.

Peter

7

If you wanted all the answers for a particular company then you could turn it round and find all the answers where survey_question.survey.company = the_company. But if you followed this route for all companies you would still have the problem of grouping the answers by company which is probably no better.

8

Maybe the other way around...

class Company   has_many :surveys

  def survey_answers     SurveyAnswer.all(:joins => {:survey_question => {:survey => :company}},                      :conditions => ['companies.id = :company_id', {:company_id => id}])   end end

Greetings, Wojtek