Rails Model.update deletes nested attachment - ruby-on-rails

Question

I have a Rails 6 app.
User has_one Shop
Shop has_one_attached Logo
User.update with nested_attributes purges the User.shop.company_logo.
class User
has_one :shop, dependent: :destroy # delete Shop if user gets deleted
accepts_nested_attributes_for :shop, # also tried reject_if: :all_blank
end
class Shop
belongs_to :user
has_one_attached :company_logo do |attachable|
attachable.variant :thumbnail, resize_to_fill: [100, 100]
end
end
# creating a User
User.create({name: "Test"})
# creating a Shop
logo = File.open(Rails.root.join('spec', 'fixtures', 'files', '400x400.png'))
Shop.create(user_id: User.last.id, name: "TestShop", company_logo: logo)
User.last.shop.company_logo.attached? # returns TRUE !!!
# Update User (deletes / detaches company_logo)
params = {name: "TestUpdateName", shop: {name: "TestUpdateShop"}}
User.last.update(params)
User.last.shop.company_logo.attached? # returns FALSE !!!
Console output:
[ActiveJob] Enqueued ActiveStorage::PurgeJob (Job ID: caebfa82-7c41-4eb9-b295-c213449e0a7e) to Async(active_storage_purge) with arguments: #<GlobalID:0x00007fcf6ae179e0 #uri=#<URI::GID gid://meta-shop/ActiveStorage::Blob/81>>
ActiveStorage::Blob Load (1.7ms) SELECT "active_storage_blobs".* FROM "active_storage_blobs" WHERE "active_storage_blobs"."id" = $1 LIMIT $2 [["id", 81], ["LIMIT", 1]]
[ActiveJob] [ActiveStorage::PurgeJob] [caebfa82-7c41-4eb9-b295-c213449e0a7e] Performing ActiveStorage::PurgeJob (Job ID: caebfa82-7c41-4eb9-b295-c213449e0a7e) from Async(active_storage_purge) enqueued at 2021-09-25T10:01:32Z with arguments: #<GlobalID:0x00007fcf5a8856b8 #uri=#<URI::GID gid://meta-shop/ActiveStorage::Blob/81>>
[ActiveJob] [ActiveStorage::PurgeJob] [caebfa82-7c41-4eb9-b295-c213449e0a7e] TRANSACTION (2.0ms) BEGIN
[ActiveJob] [ActiveStorage::PurgeJob] [caebfa82-7c41-4eb9-b295-c213449e0a7e] ActiveStorage::Attachment Exists? (2.1ms) SELECT 1 AS one FROM "active_storage_attachments" WHERE "active_storage_attachments"."blob_id" = $1 LIMIT $2 [["blob_id", 81], ["LIMIT", 1]]
[ActiveJob] [ActiveStorage::PurgeJob] [caebfa82-7c41-4eb9-b295-c213449e0a7e] ActiveStorage::Attachment Load (2.8ms) SELECT "active_storage_attachments".* FROM "active_storage_attachments" WHERE "active_storage_attachments"."record_id" = $1 AND "active_storage_attachments"."record_type" = $2 AND "active_storage_attachments"."name" = $3 LIMIT $4 [["record_id", 81], ["record_type", "ActiveStorage::Blob"], ["name", "preview_image"], ["LIMIT", 1]]
[ActiveJob] [ActiveStorage::PurgeJob] [caebfa82-7c41-4eb9-b295-c213449e0a7e] ActiveStorage::Blob Destroy (8.8ms) DELETE FROM "active_storage_blobs" WHERE "active_storage_blobs"."id" = $1 [["id", 81]]
[ActiveJob] [ActiveStorage::PurgeJob] [caebfa82-7c41-4eb9-b295-c213449e0a7e] TRANSACTION (5.1ms) COMMIT
[ActiveJob] [ActiveStorage::PurgeJob] [caebfa82-7c41-4eb9-b295-c213449e0a7e] S3 Storage (224.0ms) Deleted file from key: mx5g91bi8qwgvh6a8vzh65598kd3
[ActiveJob] [ActiveStorage::PurgeJob] [caebfa82-7c41-4eb9-b295-c213449e0a7e] S3 Storage (311.1ms) Deleted files by key prefix: variants/mx5g91bi8qwgvh6a8vzh65598kd3/
[ActiveJob] [ActiveStorage::PurgeJob] [caebfa82-7c41-4eb9-b295-c213449e0a7e] Performed ActiveStorage::PurgeJob (Job ID: caebfa82-7c41-4eb9-b295-c213449e0a7e) from Async(active_storage_purge) in 568.39ms
How can I persist the User.shop.company_logo when updating with nested_attributes ?

Answer 1

I found a solution:
My Shop model was replaced when updating through the parent User model. But there is an option which can be added on "one-to-one" relations like has_one. It's the update_only option, which is false by default. When using this, the nested model get updated and not replaced when using update_only: false
accepts_nested_attributes_for :shop, update_only: true
https://api.rubyonrails.org/classes/ActiveRecord/NestedAttributes/ClassMethods.html#method-i-accepts_nested_attributes_for