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rails--rails/activestorage/app/models/active_storage/attachment.rb
Jonathan Hefner 6aa26c30e2
Identify directly-uploaded blobs before saving the associated record
An Active Storage `Blob` must be identified before it can be reliably
validated.  For direct uploads, a `Blob` is identified when it is
attached, rather than when it is created.

Before this commit, the sequence of events when attaching a `Blob` was:

1. Find the `Blob`.
2. Assign the `Blob` to an `Attachment`.
3. Save the owner record.
4. Save the `Attachment`.
5. Identify the `Blob`'s true `content_type` from its file.
6. Save the `Blob`.

This meant that the owner record's validations might not see the
`Blob`'s true `content_type`.

After this commit, the sequence of events will be:

1. Find the `Blob`.
2. Identify the `Blob`'s true `content_type` from its file.
3. Assign the `Blob` to an `Attachment`.
4. Save the owner record.
5. Save the `Attachment`.
6. Save the `Blob`.

Thus the `Blob`'s true `content_type` will be available when running the
owner record's validations.
2020-08-11 18:08:09 -04:00

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# frozen_string_literal: true
require "active_support/core_ext/module/delegation"
# Attachments associate records with blobs. Usually that's a one record-many blobs relationship,
# but it is possible to associate many different records with the same blob. A foreign-key constraint
# on the attachments table prevents blobs from being purged if theyre still attached to any records.
#
# Attachments also have access to all methods from {ActiveStorage::Blob}[rdoc-ref:ActiveStorage::Blob].
class ActiveStorage::Attachment < ActiveRecord::Base
self.table_name = "active_storage_attachments"
belongs_to :record, polymorphic: true, touch: true
belongs_to :blob, class_name: "ActiveStorage::Blob", autosave: true
delegate_missing_to :blob
delegate :signed_id, to: :blob
after_create_commit :mirror_blob_later, :analyze_blob_later
after_destroy_commit :purge_dependent_blob_later
# Synchronously deletes the attachment and {purges the blob}[rdoc-ref:ActiveStorage::Blob#purge].
def purge
transaction do
delete
record&.touch
end
blob&.purge
end
# Deletes the attachment and {enqueues a background job}[rdoc-ref:ActiveStorage::Blob#purge_later] to purge the blob.
def purge_later
transaction do
delete
record&.touch
end
blob&.purge_later
end
private
def analyze_blob_later
blob.analyze_later unless blob.analyzed?
end
def mirror_blob_later
blob.mirror_later
end
def purge_dependent_blob_later
blob&.purge_later if dependent == :purge_later
end
def dependent
record.attachment_reflections[name]&.options[:dependent]
end
end
ActiveSupport.run_load_hooks :active_storage_attachment, ActiveStorage::Attachment