Consider these two models:
class Article < ActiveRecord::Base has_many :posts end
class Post < ActiveRecord::Base belongs_to :article end
The ActiveRecord::Dirty module allows one to detect changes in a model's attribute. In the above example, how does one detect if the number of posts an article has changed, or the posts themselves have changed from the point of view of an Article object?
In other words, is there something like "article.posts_changed?"?