1 files changed, 64 insertions, 0 deletions
diff --git a/activestorage/lib/active_storage/reflection.rb b/activestorage/lib/active_storage/reflection.rb
new file mode 100644
index 0000000000..ce248c88b5
--- /dev/null
+++ b/activestorage/lib/active_storage/reflection.rb
@@ -0,0 +1,64 @@
+# frozen_string_literal: true
+
+module ActiveStorage
+  module Reflection
+    # Holds all the metadata about a has_one_attached attachment as it was
+    # specified in the Active Record class.
+    class HasOneAttachedReflection < ActiveRecord::Reflection::MacroReflection #:nodoc:
+      def macro
+        :has_one_attached
+      end
+    end
+
+    # Holds all the metadata about a has_many_attached attachment as it was
+    # specified in the Active Record class.
+    class HasManyAttachedReflection < ActiveRecord::Reflection::MacroReflection #:nodoc:
+      def macro
+        :has_many_attached
+      end
+    end
+
+    module ReflectionExtension # :nodoc:
+      def add_attachment_reflection(model, name, reflection)
+        model.attachment_reflections = model.attachment_reflections.merge(name.to_s => reflection)
+      end
+
+      private
+        def reflection_class_for(macro)
+          case macro
+          when :has_one_attached
+            HasOneAttachedReflection
+          when :has_many_attached
+            HasManyAttachedReflection
+          else
+            super
+          end
+        end
+    end
+
+    module ActiveRecordExtensions
+      extend ActiveSupport::Concern
+
+      included do
+        class_attribute :attachment_reflections, instance_writer: false, default: {}
+      end
+
+      module ClassMethods
+        # Returns an array of reflection objects for all the attachments in the
+        # class.
+        def reflect_on_all_attachments
+          attachment_reflections.values
+        end
+
+        # Returns the reflection object for the named +attachment+.
+        #
+        #    User.reflect_on_attachment(:avatar)
+        #    # => the avatar reflection
+        #
+        def reflect_on_attachment(attachment)
+          attachment_reflections[attachment.to_s]
+        end
+      end
+    end
+  end
+end