Rails 3. How to add a helper that ActiveAdmin will use?
You can define them in app/helpers/ as you tried but you need to include them trough the active admin's initializer like this:
# in config/initializers/active_admin.rb
ActiveAdmin.setup do |config|
....
end
module ActiveAdmin::ViewHelpers
include ApplicationHelper
end
You need to put your helper functions in app/helpers/active_admin/views_helper.rb file
Example:
module ActiveAdmin::ViewsHelper #camelized file name
def my_helper
# do something
end
end