Associations with Conditions

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Associations with Conditions

You can specify ActiveRecord Associations with a condition on them:

class Post
  has_many :comments
  has_many :published_comments,
           :class_name => "Comment",
           :conditions => { :published => true }
end

One possible use-case is that you can use these associations to eager load only a subset of the associated records:

post = Post.find(1, :include => :published_comments)
# SELECT "posts".* FROM "posts" WHERE "posts"."id" = ? LIMIT 1  [["id", 1]]
# SELECT "comments".* FROM "comments" WHERE "comments"."post_id" IN (1) AND ("comments"."published" = 't')

Read more about this in the API docs about ActiveRecord::Associations.

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