CODEWITHSUNDEEP
ruby-on-railsactiverecord
user797963
user797963

Reputation: 3027

Rails - using results form a one to many query

I'm building a simple rails application as a learning project, and am having trouble figuring out how to actually use the results from a one to many query. As far as I can tell, the query itself is fine, but I can't seem to use the results.

Here's my db schema:

  create_table "tests", force: true do |t|
    t.string   "name"
    t.integer  "subject_id"
    t.string   "description"
  end

  create_table "questions", force: true do |t|
    t.text     "question"
    t.integer  "test_id"
  end

  create_table "answers", force: true do |t|
    t.integer  "question_id"
    t.text     "answer"
  end

Here are my models:

class Test < ActiveRecord::Base
    has_many :questions
    belongs_to :subject
end

class Question < ActiveRecord::Base
    has_many :answers
    belongs_to :test
end

class Answer < ActiveRecord::Base
    belongs_to :questions
end

Now, in the controller I'm using, I'm setting an instance variable with this Active Record query (hardcoded the test_id for now):

@questionSet = Question.includes(:answers).where("test_id = ?", 1)

I can then go and get all of the questions out of the view, but how do I get the answers as well? It's like I need a nested for loop - one to loop through the questions, then another to get all answers where question_id matches the id in the question object. These active record objects are a bear to work with.

Here's what I have, which will output the questions, but I cannot get the answers to output:

<% @questions.each do |q| %>
    <%= q.question %>
    <!--need to loop through answers and output answers for this question (where quesiton_id)-->
    <br>
    <br>
<% end %>

How do I loop through my answer active record objects and output them if question_id = q.id?

Upvotes: 1

Views: 885

Answers (1)

Kirti Thorat
Kirti Thorat

Reputation: 53038

A Question has_many Answers. As you have set has_many relationship, rails will create a dynamic method for you in Question model as answers. Upon calling answers method on an instance of Question, you will get all the answers for that particular question.

For eg:

q = Question.find(10) ## Returns Question record with id 10 from questions table
q.answers   ## Returns all the answers mapped to question with id 10

q.answers will result in a query as below:

 SELECT "answers".* FROM "answers" WHERE "answers"."question_id" = ? [["question_id", 10]]

In your case, you can modify the view code as below: 

<% @questions.each do |q| %>
    <%= q.question %>
    <% q.answers.each do |a| %>
       <%= a.answer %>
    <% end %> 
    <br>
    <br>
<% end %>

Upvotes: 4

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