Add Filter ActiveStorage Blobs To Only Images as a Rails TIL

Author: jbranchaud

README.md

@@ -10,7 +10,7 @@ pairing with smart people at Hashrocket.
 
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@@ -1022,6 +1022,7 @@ If you've learned something here, support my efforts writing daily TILs by
 - [Ensure A Rake Task Cannot Write Data](rails/ensure-a-rake-task-cannot-write-data.md)
 - [Ensure Migrations Use The Latest Schema](rails/ensure-migrations-use-the-latest-schema.md)
 - [Ensure Record Saved With after_commit Callback](rails/ensure-record-saved-with-after-commit-callback.md)
+- [Filter ActiveStorage Blobs To Only Images](rails/filter-active-storage-blobs-to-only-images.md)
 - [Find Or Create A Record With FactoryBot](rails/find-or-create-a-record-with-factory-bot.md)
 - [Find Records With Multiple Associated Records](rails/find-records-with-multiple-associated-records.md)
 - [Force All Users To Sign Out](rails/force-all-users-to-sign-out.md)

rails/filter-active-storage-blobs-to-only-images.md

@@ -0,0 +1,30 @@
+# Filter ActiveStorage Blobs To Only Images
+
+If your Rails app is using `ActiveStorage` for both images and ActionMailbox
+emails, then you're going to have a mix of both in the `active_storage_blobs`
+table.
+
+```sql
+> select id, filename, content_type from active_storage_blobs limit 2;
+
+| id | filename           | content_type   |
+|----|--------------------|----------------|
+|  1 | shirt-brothers.jpg | image/jpeg     |
+|  2 | message.eml        | message/rfc822 |
+```
+
+In that case, you are going to want to make sure that any part of your system
+that only cares to deal with images filters down to only blobs where the
+`content_type` is one that you care about.
+
+I expect that there might be a couple different image `content_type` values
+that my system handles, so I filter my `active_storage_blobs` like so:
+
+
+```ruby
+@images =
+  ActiveStorage::Blob
+    .where(content_type: %w[image/jpeg image/png image/gif image/webp])
+    .order(created_at: :desc)
+    .first(10)
+```