Question

If I have a has_and_belongs_to_many relationship between two models, let’s say Users and Accounts, can I require that a User have at least one Account, and how?

Also, using the has_and_belongs_to_many relationship, is it possible for an Account not to have a User?

What I need is a relationship where Accounts can live on their own, and belong to Billers, but they can also belong to Users if a User signed up with one. Is this possible, and how?

Answer 1

I personally would drop the the HABTM. Instead I would use has_many :though=>

You would need to create two new models, account_users, and account_billers. You likely already have join tables for the HABTM, but this will expose them as models so they will need ID fields.

So you would end up with something like the following:

class Account < ActiveRecord::Base
  has_many :account_billers
  has_many :account_users

  has_many :billers, :through=> :account_billers
  has_many :users, :through=> :account_users
end

class User < ActiveRecord::Base
  has_many :account_users
  has_many :accounts, :through=>:account_users

  validates :accounts, :length => { :minimum => 1}
end

class Biller < ActiveRecord::Base
  has_many :account_billers
  has_many :accounts, :through=>:account_billers

  validates :accounts, :length => { :minimum => 1}
end

class AccountUser < ActiveRecord::Base
  belongs_to :user
  belongs_to :account
end

class AccountBiller < ActiveRecord::Base
  belongs_to :biller
  belongs_to :account
end