On 1 August 2012 02:17, Neil Mowbray <[email protected]> wrote: > Unless I'm being dumb I cannot find anything on Google search or in the > Rails books on how to create a one-to-one polymorphic association > (as apposed to a one-to-many polymorphic association).
Change the has_many to a has_one, and you should have a 1:1 relationship... > - Person > generic concept (name, age, nationality, etc) which I want to attach > polymorphically to concrete models suchs > > concrete class contain additional type specific information which I do not > want nullable hence STI is not desirable > and would result in a sparse table. I would still consider STI for this kind of situation, but I'd give each subclass a different association to the specific information for that model, which would keep the DB nice and 'clean' (I did it yesterday with Vehicles, and sub-classes for Car, Truck, Bus, Motorbike, etc,) class Person < AR::Base end class Staff < Person # employee number, start date, etc has_one :staff_details end class Mother < Person # can't imagine what info "mother" would need, but there's support for it has_one :mother_details end class Child < Person # what does a child need differently? has_one :child_details end Of course, the problem with this approach is what happens when you have a staff member who is a mother? You'd need two records for them (it's easy for me; a Car can't also be a Motorbike :-) In this event you would be better coming from a different angle (like a "has_many :employments" to determine whether a Person is staff or not, and a "has_many :parentings" to figure whether they're a mother or father) HTH -- 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 https://groups.google.com/groups/opt_out.
