ActiveAdmin with has_many problem; undefined method 'new_record?'
Solution 1:
go to your Recipe model and add the following line
accepts_nested_attributes_for :steps
The line is required by formtastic, not active admin. Check https://github.com/justinfrench/formtastic for formtastic documentation
Solution 2:
class Recipe < ActiveRecord::Base
attr_accessible :step_attributes
has_many :steps
accepts_nested_attributes_for :steps
end