Creating ActiveRecord query to always show an exam not previously done by student (Rails app)-CodePudding

On this feature I'm adding to my school's app, an User has a new Checkup (a short English test) being presented by the system for them to do every 4 weeks. I want to build a query that always retrieves from the database a Checkup that hasn't been previously answered by the student. Since the models are associated, I believe this is simple, but I do not know how to code the query using Rails (have done research and wasn't able to find an answer). There are three models to be considered here: User, Answer and Checkup. I have a separate Answer model for the answers the students give, because they have to be processed separately due to other features of the app. This is the User model:

 class User < ApplicationRecord
    has_many :answers
 end

This is the Answer model:

class Answer < ApplicationRecord

   belongs_to :user
   belongs_to :checkup

end

And this is the Checkup model

class Checkup < ApplicationRecord
   has_many :answers
end

In the controller of the page where the Checkup is shown, I wish to have a variable in the page's action that holds the retrieved Checkup:

def exams
   @next_checkup = #the ActiveRecord query goes here 
end

The query needs to retrieve a Checkup that doesn't have in its related answers an answer given by the current user (the user of an answer can be retrieved by the attribute "user_id"). How should I code the query? Thanks!

CodePudding user response：

I would try:

@next_checkup = Checkup.where.not(id: current_user.answers.pluck(:checkup_id)).first