Rails habtm and finding record with no association

Question

I have 2 models:

class User < ActiveRecord::Base
    has_and_belongs_to_many :groups
end

class Group < ActiveRe         


        

Answer 1

Your implicit join table would have been named groups_users based on naming conventions. Confirm it once in your db. Assuming it is:

In newer Rails version:

scope :not_in_any_group, -> {
    joins("LEFT JOIN groups_users ON users.id = groups_users.user_id")
    .where("groups_users.user_id IS NULL")
}

For older Rails versions:

scope :not_in_any_group, {
    :joins      => "LEFT JOIN groups_users ON users.id = groups_users.user_id",
    :conditions => "groups_users.user_id IS NULL",
    :select     => "DISTINCT users.*"
}