1 files changed, 76 insertions, 0 deletions
diff --git a/activestorage/lib/active_storage/attached/macros.rb b/activestorage/lib/active_storage/attached/macros.rb
new file mode 100644
index 0000000000..89297e5bdf
--- /dev/null
+++ b/activestorage/lib/active_storage/attached/macros.rb
@@ -0,0 +1,76 @@
+# Provides the class-level DSL for declaring that an Active Record model has attached blobs.
+module ActiveStorage::Attached::Macros
+  # Specifies the relation between a single attachment and the model.
+  #
+  #   class User < ActiveRecord::Base
+  #     has_one_attached :avatar
+  #   end
+  #
+  # There is no column defined on the model side, Active Storage takes
+  # care of the mapping between your records and the attachment.
+  #
+  # Under the covers, this relationship is implemented as a `has_one` association to a
+  # `ActiveStorage::Attachment` record and a `has_one-through` association to a
+  # `ActiveStorage::Blob` record. These associations are available as `avatar_attachment`
+  # and `avatar_blob`. But you shouldn't need to work with these associations directly in
+  # most circumstances.
+  #
+  # The system has been designed to having you go through the `ActiveStorage::Attached::One`
+  # proxy that provides the dynamic proxy to the associations and factory methods, like `#attach`.
+  #
+  # If the +:dependent+ option isn't set, the attachment will be purged
+  # (i.e. destroyed) whenever the record is destroyed.
+  def has_one_attached(name, dependent: :purge_later)
+    define_method(name) do
+      instance_variable_get("@active_storage_attached_#{name}") ||
+        instance_variable_set("@active_storage_attached_#{name}", ActiveStorage::Attached::One.new(name, self))
+    end
+
+    has_one :"#{name}_attachment", -> { where(name: name) }, class_name: "ActiveStorage::Attachment", as: :record
+    has_one :"#{name}_blob", through: :"#{name}_attachment", class_name: "ActiveStorage::Blob", source: :blob
+
+    if dependent == :purge_later
+      before_destroy { public_send(name).purge_later }
+    end
+  end
+
+  # Specifies the relation between multiple attachments and the model.
+  #
+  #   class Gallery < ActiveRecord::Base
+  #     has_many_attached :photos
+  #   end
+  #
+  # There are no columns defined on the model side, Active Storage takes
+  # care of the mapping between your records and the attachments.
+  #
+  # To avoid N+1 queries, you can include the attached blobs in your query like so:
+  #
+  #   Gallery.where(user: Current.user).with_attached_photos
+  #
+  # Under the covers, this relationship is implemented as a `has_many` association to a
+  # `ActiveStorage::Attachment` record and a `has_many-through` association to a
+  # `ActiveStorage::Blob` record. These associations are available as `photos_attachments`
+  # and `photos_blobs`. But you shouldn't need to work with these associations directly in
+  # most circumstances.
+  #
+  # The system has been designed to having you go through the `ActiveStorage::Attached::Many`
+  # proxy that provides the dynamic proxy to the associations and factory methods, like `#attach`.
+  #
+  # If the +:dependent+ option isn't set, all the attachments will be purged
+  # (i.e. destroyed) whenever the record is destroyed.
+  def has_many_attached(name, dependent: :purge_later)
+    define_method(name) do
+      instance_variable_get("@active_storage_attached_#{name}") ||
+        instance_variable_set("@active_storage_attached_#{name}", ActiveStorage::Attached::Many.new(name, self))
+    end
+
+    has_many :"#{name}_attachments", -> { where(name: name) }, as: :record, class_name: "ActiveStorage::Attachment"
+    has_many :"#{name}_blobs", through: :"#{name}_attachments", class_name: "ActiveStorage::Blob", source: :blob
+
+    scope :"with_attached_#{name}", -> { includes("#{name}_attachments": :blob) }
+
+    if dependent == :purge_later
+      before_destroy { public_send(name).purge_later }
+    end
+  end
+end