OK, just got:
class User
include Mongoid::Document
# devise stuff...
has_one :card
end
class Card
include Mongoid::Document
belongs_to :user
end
irb(main):012:0> user = User.new(email: "test@test.com", password: "testtest",password_confirmation: "testtest")
=> #<User _id: 4f4e1b1494b3023d34000003, _type: nil, email: "test@test.com", encrypted_password: "$2a$10$yCdmjfgK94VrIec062ZXFuoTuApFFaFsDSOVEutoklcSGc4SQH2MG", reset_password_token: nil, reset_password_sent_at: nil, remember_created_at: nil, sign_in_count: 0, current_sign_in_at: nil, last_sign_in_at: nil, current_sign_in_ip: nil, last_sign_in_ip: nil>
irb(main):013:0> user.build_card uuid: "test"
=> #<Card _id: 4f4e1b2094b3023d34000004, _type: nil, created_at: nil, updated_at: nil, uuid: "test", user_id: BSON::ObjectId('4f4e1b1494b3023d34000003')>
irb(main):014:0> user.new_record?
=> true
irb(main):015:0> user.card.new_record?
=> true
irb(main):016:0> user.save
=> true
irb(main):017:0> user.card.new_record?
=> true
irb(main):018:0> User.count
=> 1
irb(main):019:0> Card.count
=> 0
Thanks!
OK I need to use