module ActiveAdmin::ViewHelpers::DisplayHelper

def display_name_method_for(resource)

Looks up and caches the first available display name method. 
def display_name_method_for(resource)
  @@display_name_methods_cache ||= {}
  @@display_name_methods_cache[resource.class] ||= begin
    methods = active_admin_application.display_name_methods - association_methods_for(resource)
    methods.detect{ |method| resource.respond_to? method }
  end
end