helper gotchas

refs activeadmin#3671

docs/14-gotchas.md

@@ -9,4 +9,44 @@ session from being committed. Flash messages won't work and you will be unable t
 use the session for storing anything.
 
 For more information see the following post: 
-[http://www.intridea.com/blog/2013/3/20/rails-assets-prefix-may-disable-your-session](http://www.intridea.com/blog/2013/3/20/rails-assets-prefix-may-disable-your-session)
+[http://www.intridea.com/blog/2013/3/20/rails-assets-prefix-may-disable-your-session](http://www.intridea.com/blog/2013/3/20/rails-assets-prefix-may-disable-your-session)
+
+## Helpers
+
+There are two knowing gotchas with helpers. This hopfully will help you to
+find a solution.
+
+### Helpers are not reloading in development
+
+This is a known and still open [issue](https://github.com/activeadmin/activeadmin/issues/697)
+the only way is to restart your server each time you change a helper.
+
+### Helper maybe not included by default
+
+If you use `config.action_controller.include_all_helpers = false` in your application config, 
+you need to include it by hand.
+
+#### Solutions
+
+##### First use a monky patch
+
+This works for all ActiveAdmin rources at once.
+
+```ruby
+# config/initializers/active_admin_helpers.rb
+ActiveAdmin::BaseController.class_eval do
+  helper ApplicationHelper
+end
+```
+
+##### Second use the `controller` method
+
+This works only for one resource at a time.
+
+```ruby
+ActiveAdmin.register User do
+  controller do
+    helper UserHelper
+  end
+end
+```