app/serializers/direct_message_serializer.rb
class DirectMessageSerializer < ActiveModel::Serializer
attributes :id, :user_id, :to_user_id, :content_type, :content, :time_created_at, :unread_count
def time_created_at
object.created_at.to_i
end
def unread_count
current_user = serialization_options[:current_user]
return 0 unless current_user
current_user.unread_dm_between((current_user&.id == user_id) ? to_user_id : user_id).count
end
has_one :user, serializer: UserBasicSerializer
has_one :to_user, serializer: UserBasicSerializer
end