Strange behaviour with the "create_xxx" on has_one association

[Man Vuong Ha Thanh]

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:

$ user.create_user_preference

 (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

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??

[Vivek Sampara]

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

   

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[Frederick Cheung]

On Monday, December 8, 2014 8:48:37 AM UTC, Man Vuong Ha Thanh wrote:

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??

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

[Vivek Sampara]

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

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