CODEWITHSUNDEEP
ruby-on-railsrubymodel
CloudBSD
CloudBSD

Reputation: 106

How to express sometimes has one relationship in rails

When we ask question in stackoverflow, and somebody answer your question, then the model relationship will be 

class Question < ActiveRecord::Base
  has_many :answers
end

class Answer < ActiveRecord::Base
  belongs_to :question
end

you will take one answer as the best answer of your question, then the relationship is 

class Question
  has_one answer (the best one)
end

but sometimes, question hasn't best answer (such as: no answer is provided)

my question is how to express the relationship between Question an BEST answer.

Upvotes: 1

Views: 204

Answers (2)

Aleksei Matiushkin
Aleksei Matiushkin

Reputation: 121010

A bit superfluous solution, but if you need to implement (0..1) multiplicity with standard rails relationship DSL, you may use through relation:

class Question < ActiveRecord::Base
  has_many :answers
  has_one  :answer, :through => :bestanswers
end

class Answer < ActiveRecord::Base
  belongs_to :question
  has_one :bestanswer
end

class BestAnswer < Answer
  belongs_to :answer
  belongs_to :question
end

Upvotes: 1

nikolayp
nikolayp

Reputation: 17949

$> rails g migration add_best_to_answers best:boolean

> a = Answer.first
> a.best = true
> a.save
> q = a.question 
> q.a.best? # => true

Upvotes: 2

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