CODEWITHSUNDEEP
ruby-on-railsrails-models
Rahul
Rahul

Reputation: 47146

how to fetch a model using the order by of an associated model?

I have Models A and B. A has_many B. Now I wanna fetch all the records of A ordered by the B's updated_at. Is it possible to write a find function for this?

Upvotes: 0

Views: 59

Answers (3)

Mischa
Mischa

Reputation: 43318

Instead of A and B, lets say a Teacher has many Students:

teachers = Teacher.joins(:students).order('students.updated_at').uniq

Upvotes: 1

Rob Mack
Rob Mack

Reputation: 26

Try something like this:

A.find(:all, :include => ['Bs'], :order => 'Bs.updated_at')

Upvotes: 1

Arun Kumar Arjunan
Arun Kumar Arjunan

Reputation: 6857

It doesn't makes sense when A has many Bs.

Consider the example:

A1 => [B1, B2]
A2 => [B3, B4]

Assuming the following:

B1.updated_at => 2.days.ago
B2.updated_at => 1.day.ago

B3.updated_at => 4.days.ago
B4.updated_at => 1.days.from_now

Now which one should come first, A1 or A2?

Upvotes: 0

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