Strange behaviour with the "create_xxx" on has_one association

rubyonrails-talk
1

I have models like this:

class User < ActiveRecord::Base has_one :user_preference, dependent: :destroy end

class UserPreference < ActiveRecord::Base belongs_to :user end

``

It works fine when I call this:

(0.3ms) BEGIN

User Load (0.9ms) SELECT “users”.* FROM “users” WHERE “users”.“deleted_at” IS NULL AND “users”.“id” = $1 LIMIT 1 [[“id”, “055df158-4b3f-43f0-b73a-0c14e0ba7723”]]

UserPreference Exists (0.7ms) SELECT 1 AS one FROM “user_preferences” WHERE “user_preferences”.“user_id” = ‘055df158-4b3f-43f0-b73a-0c14e0ba7723’ LIMIT 1

SQL (0.5ms) INSERT INTO “user_preferences” (“created_at”, “updated_at”, “user_id”) VALUES ($1, $2, $3) RETURNING “id” [[“created_at”, “2014-12-08 08:45:57.630670”], [“updated_at”, “2014-12-08 08:45:57.630670”], [“user_id”, “055df158-4b3f-43f0-b73a-0c14e0ba7723”]]

(1.5ms) COMMIT

(0.2ms) BEGIN

(0.2ms) COMMIT

$ user.create_user_preference

``

But, if I call that method again, it will delete the profile record.

$ user.create_user_preference

(0.3ms) BEGIN User Load (0.8ms) SELECT “users”.* FROM “users” WHERE “users”.“deleted_at” IS NULL AND “users”.“id” = $1 LIMIT 1 [[“id”, “055df158-4b3f-43f0-b73a-0c14e0ba7723”]] UserPreference Exists (0.7ms) SELECT 1 AS one FROM “user_preferences” WHERE “user_preferences”.“user_id” = ‘055df158-4b3f-43f0-b73a-0c14e0ba7723’ LIMIT 1 (0.3ms) ROLLBACK (0.2ms) BEGIN SQL (0.4ms) DELETE FROM “user_preferences” WHERE “user_preferences”.“id” = $1 [[“id”, “9eb6cabd-7c50-4f2b-8562-1159e1c2f4b4”]] (37.0ms) COMMIT

``

It looks weird for me. Is it a normal behaviour, or am I doing something wrong??

2

This behavior is normal. When a record already exists for has_one, it deletes the previously existing record for database consistency ( has_many ) . It is a bit similar to has_and_belongs_to_many

when you have User has_and_belongs_to_many categories.

user.categories_ids = [4,5,6] #some array of category ids

its deletes all the existing records and replace it with the new ones.

Cheers

3

Well the delete makes sense to me - you’re creating a new user preference, so the old one should be destroyed since this is a has_one and you’ve configured the relationship as dependent: :destroy. Not sure why it doesn’t create a new one though

Fred

4

The new one is obviously failing a validation on the user or user_preference . Check the object for any validation errors.