Rails join query

Question

I am pretty new in rails and honestly, I am struggling with queries even after multiple researchs. Here is my simple schema:

So basically, a question has many options, an option belongs to a question and has many answer, and an answer belongs to an option and has many users.

I don't think it s necessary to post the models code since it is just like i mentioned above.

What i would like to do is given a question option, see if a particular user already checked it (so look in the answer table if there is a row matching a given id_option, user_id and user_type). So in my haml loop, when displaying the different question option, i'm calling a method of my question_option model just like this :

- question.question_option.all.each do |option| #{option.title} .check - if option.selected_by(current_actor) = check_box_tag(option.id, "checked",true, class: 'styled-checkbox') - else = check_box_tag(option.id, "checked",false, class: 'styled-checkbox')

and the method called :

def selected_by(answerer) answer_match = ::Vacancies::QuestionOption .joins(:answers) .where(answerer_id: answerer.id, answerer_type:answerer.type ) response = answer_match.find(self.id) return response end

This method is located in my QuestionOption model and leads to no errors but it s not working ever. Can you help me transform this query to make it work with ActiveRecord ? Thanks

"I don't think it s necessary to post the models code since it is just like I mentioned above.", please do it. Personally, it's easier to see the models and know how to replicate your scenario. — Sebastián Palma
– Sebastián Palma, Commented Mar 30, 2021 at 9:44
You are right i should have done it but since i resolved the problem i think this is not necessary anymore. Anyway, thanks for your interest to it. :D — Matthieu Rioual
– Matthieu Rioual, Commented Mar 30, 2021 at 10:09
You should post your solution below if you resolved it yourself. — Cassandra S.
– Cassandra S., Commented Mar 30, 2021 at 11:02

Sachin Singh · Accepted Answer · 2021-03-31 18:55:44Z

1

Try the below code. It checks if there are any answers by the user passed in the params on the question. I think this is what you intended to do as well-

def selected_by(answerer) answers = Answer.where(answerer_id: answerer.id, answerer_type:answerer.type, id_option: self.id) answers.exists? end

edited Mar 31, 2021 at 18:55

answered Mar 30, 2021 at 11:02

Sachin Singh

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2 Comments

Int'l Man Of Coding Mystery Over a year ago

Might be more performant to use exists? at the end of the query instead of saving to variable and calling present?. also could just use .where(answerer: answerer), Rails magic will compare both the type and id there. And then one final nag, since your expecting a boolean, it's convention to use a predicate method, ie def selected_by?(answerer)

Sebastián Palma Over a year ago

You passed from loading a single database record to query all of them and do nothing with them, as stated by @Int'lManOfCodingMystery, the best improvement is to use exists? if you don't need to access any records' columns.

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