Is there a Rails way to get all associated objects of an ActiveRecord::Relation?

Question

Let's suppose we've 2 models:

class Author < ApplicationRecord
  has_many :books
end

class Book < ApplicationRecord
  belongs_to :author
end

and we want to get a list of all Books - on a page where we're already querying all Authors along with their associated books as follow:

@authors = Author.all.includes(:books)

We could do it using Ruby as so:

@authors.map(&:books) # returns an ActiveRecord::Associations::CollectionProxy

But is there a Rails' way of doing it that would return an ActiveRecord::Relation ?

Answer 1

extract_associated(association)

Extracts a named association from the relation. The named association is first preloaded, then the individual association records are collected from the relation. Like so:

account.memberships.extract_associated(:user)
# => Returns collection of User records

This is short-hand for:

  account.memberships.preload(:user).collect(&:user)

https://api.rubyonrails.org/classes/ActiveRecord/QueryMethods.html#method-i-extract_associated