问题
The scenario is:
How can an Account give ratings to another account? This results in two lists on the Account. Those who I have rated and those who have rated me. (my_ratings and ratings_given)
This boils down to:
How can multiple 1 - N relationsips to the same entity work in Mongoid?
In Mongoid's Docs it says you can use has_many
and belongs_to
to link the entities together.
I currently have this on Account
has_many :ratings, :as => "my_ratings"
has_many :ratings, :as => "ratings_given"
and this on Ratings:
belongs_to :user, :as => 'Rater'
belongs_to :user, :as => 'Ratie'
The docs don't cover this case, so I thought you would have to differentiate between the two with an :as parameter.
Is this even remoting correct?
回答1:
You can achieve what you want using the class_name and inverse_of options:
class Account
include Mongoid::Document
field :name
has_many :ratings_given, :class_name => 'Ratings', :inverse_of => :rater
has_many :my_ratings, :class_name => 'Ratings', :inverse_of => :ratee
end
class Ratings
include Mongoid::Document
field :name
belongs_to :rater, :class_name => 'Account', :inverse_of => :ratings_given
belongs_to :ratee, :class_name => 'Account', :inverse_of => :my_ratings
end
The documentation has changed since I was last working with it so I wasn't sure whether this is still the recommended approach. Looks like it doesn't mention these options on the 1-many referenced page. But if you take a look at the general page on relations they are covered there.
In any case you need to explicitly link ratings_given/rater and my_ratings/ratee associations when there are two associations to the same class, otherwise mongoid has no way to know which of the two potential inverses to pick.
来源:https://stackoverflow.com/questions/6394290/two-1-n-relations-in-mongoid-rails