the “through” relation is missing; it covers has_and_belongs_to_many, as well as a manual way of doing through, but not through itself; it would be useful to add
” Having additional attributes on the join table of a has_and_belongs_to_many association is deprecated and will be removed in Rails 3.1.” by Rails3.0.4 Console. “Ruby on Rails Tutorial” by Michael Hartl do not use “has_and_belongs_to_many”.
I think the question is why isn’t the has_many :through relationship not covered?
I wondered this too. There seems to be a lot missing from this book - accepts_nested_attributes_for is another topic missing.
They’ve cut the book in half it appears - the previous version was 700+ pages this one is 400+. It’s still a decent book but no longer seems to be the definitive guide.