1 files changed, 56 insertions, 0 deletions
diff --git a/activestorage/lib/active_storage/attached/one.rb b/activestorage/lib/active_storage/attached/one.rb
new file mode 100644
index 0000000000..0c522e856e
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+++ b/activestorage/lib/active_storage/attached/one.rb
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+# Representation of a single attachment to a model.
+class ActiveStorage::Attached::One < ActiveStorage::Attached
+  delegate_missing_to :attachment
+
+  # Returns the associated attachment record.
+  #
+  # You don't have to call this method to access the attachment's methods as
+  # they are all available at the model level.
+  def attachment
+    record.public_send("#{name}_attachment")
+  end
+
+  # Associates a given attachment with the current record, saving it to the database.
+  # Examples:
+  #
+  #   person.avatar.attach(params[:avatar]) # ActionDispatch::Http::UploadedFile object
+  #   person.avatar.attach(params[:signed_blob_id]) # Signed reference to blob from direct upload
+  #   person.avatar.attach(io: File.open("~/face.jpg"), filename: "face.jpg", content_type: "image/jpg")
+  #   person.avatar.attach(avatar_blob) # ActiveStorage::Blob object
+  def attach(attachable)
+    write_attachment \
+      ActiveStorage::Attachment.create!(record: record, name: name, blob: create_blob_from(attachable))
+  end
+
+  # Returns true if an attachment has been made.
+  #
+  #   class User < ActiveRecord::Base
+  #     has_one_attached :avatar
+  #   end
+  #
+  #   User.new.avatar.attached? # => false
+  def attached?
+    attachment.present?
+  end
+
+  # Directly purges the attachment (i.e. destroys the blob and
+  # attachment and deletes the file on the service).
+  def purge
+    if attached?
+      attachment.purge
+      write_attachment nil
+    end
+  end
+
+  # Purges the attachment through the queuing system.
+  def purge_later
+    if attached?
+      attachment.purge_later
+    end
+  end
+
+  private
+    def write_attachment(attachment)
+      record.public_send("#{name}_attachment=", attachment)
+    end
+end