Al Rowan wrote in post #960389: > Hi, > I'm fairly new to RoR and I'm trying to figure out the best way to deal > with Users in my application. I've got (for the purpose of this thread) > 3 models, User, Subject, and SubjectUserAssignment. > > The user model is joined to the Subject model with the following, > creating a many to many relationship between User and Subject: > > has_many :subjects, :through => :subject_user_assignments > has_many :subject_user_assignments > > Likewise, the Subject model: > > has_many :users, :through => :subject_user_assignments > has_many :subject_user_assignments > belongs_to :user, :foreign_key => "user_id_created" > belongs_to :user, :foreign_key => "user_id_updated" > > This works fine, I can return all users for a given subject, and all > subjects for a given user. The problem is that the Subject model has > user_id_created and user_id_updated fields, which contain the user_id of > the user(s) who created and updated the subject. So a user can either be > related to a subject because they're assigned to it, or because they > created/updated it, or both. How do I go about specifying this in my > User model? User.subjects should return all subjects assigned to a user, > but I need something else like User.created_subjects to show all > subjects created by a user. Am I using :foreign_key correctly in the > Subject model?
First, unless you fear naming conflicts I think and Assignment model would stand on it's own so I'll present my suggestion based on that. User ----------- has_many :assignments has_many :subjects, :through => :assignments Assignment ----------- belongs_to :user belongs_to :subject Subject ----------- has_many :assignments has_many :users, :through => :assignments This takes care of the many-to-many association: user.assignments user.subjects subject.assignments subject.users Now you have two additional one-to-many associations between User and Subject. A Subject has only one creator and one last_updater. So add two foreign keys created_by_id and last_updated_by_id to the Subject model and define the associations: User ----------- has_many :assignments has_many :subjects, :through => :assignments has_many :created_subjects, :class => "Subject", :foreign_key => :created_by_id has_many :last_updated_subjects, :class => "Subject", :foreign_key => :last_updated_by_id Subject ----------- has_many :assignments has_many :users, :through => :assignments belongs_to :creator, :class => "User", :foreign_key => :created_by_id belongs_to :last_updater, :class => "User", :foreign_key => :last_updated_by_id Which adds: user.created_subjects user.last_updated_subjects subject.creator subject.last_updater -- Posted via http://www.ruby-forum.com/. -- You received this message because you are subscribed to the Google Groups "Ruby on Rails: Talk" group. To post to this group, send email to [email protected]. To unsubscribe from this group, send email to [email protected]. For more options, visit this group at http://groups.google.com/group/rubyonrails-talk?hl=en.
