1 files changed, 28 insertions, 5 deletions
diff --git a/activestorage/lib/active_storage/attached/one.rb b/activestorage/lib/active_storage/attached/one.rb
index 2e5831348e..0244232b2c 100644
--- a/activestorage/lib/active_storage/attached/one.rb
+++ b/activestorage/lib/active_storage/attached/one.rb
@@ -14,18 +14,20 @@ module ActiveStorage
     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(io: File.open("/path/to/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))
+      if attached? && dependent == :purge_later
+        replace attachable
+      else
+        write_attachment build_attachment_from(attachable)
+      end
     end
 
-    # Returns true if an attachment has been made.
+    # Returns +true+ if an attachment has been made.
     #
     #   class User < ActiveRecord::Base
     #     has_one_attached :avatar
@@ -36,6 +38,14 @@ module ActiveStorage
       attachment.present?
     end
 
+    # Deletes the attachment without purging it, leaving its blob in place.
+    def detach
+      if attached?
+        attachment.destroy
+        write_attachment nil
+      end
+    end
+
     # Directly purges the attachment (i.e. destroys the blob and
     # attachment and deletes the file on the service).
     def purge
@@ -53,6 +63,19 @@ module ActiveStorage
     end
 
     private
+      def replace(attachable)
+        blob.tap do
+          transaction do
+            detach
+            write_attachment build_attachment_from(attachable)
+          end
+        end.purge_later
+      end
+
+      def build_attachment_from(attachable)
+        ActiveStorage::Attachment.new(record: record, name: name, blob: create_blob_from(attachable))
+      end
+
       def write_attachment(attachment)
         record.public_send("#{name}_attachment=", attachment)
       end