I think I''ve just thoroughly confused myself at this point. I have a
class that has a has_many and has_one relationship that use the same
object.
Here is an example:
class Person < ActiveRecord::Base
has_many :hobbies
has_one :favorite_hobby, :class_name => "Hobby"
end
class Hobby < ActiveRecord::Base
belongs_to :person
belongs_to :person, :foreign_key => "favorite_hobby_id"
end
Of course, this doesn''t work. Any ideas what I need to change to get
this to work properly?
Thanks.
--
Posted via http://www.ruby-forum.com/.
The Barge wrote:> I think I''ve just thoroughly confused myself at this point. I have a > class that has a has_many and has_one relationship that use the same > object. > > Here is an example: > > class Person < ActiveRecord::Base > has_many :hobbies > has_one :favorite_hobby, :class_name => "Hobby" > end > > class Hobby < ActiveRecord::Base > belongs_to :person > belongs_to :person, :foreign_key => "favorite_hobby_id" > end > > Of course, this doesn''t work. Any ideas what I need to change to get > this to work properly? > > Thanks.I think you should be using habtm for the hobbies (two people can enjoy the same hobby, right?) and an additional belongs_to for the favorite. This may seem counterintuitive, but remember that belongs_to is used on the table with the foreign key field (which in this case is people.favorite_hobby_id). So: class Person habtm :hobbies belongs_to :favorite_hobby, :class_name => ''Hobby'' end class Hobby habtm :people # reverse association probably unnecessary for favorite_hobby end Best, -- Marnen Laibow-Koser http://www.marnen.org marnen-sbuyVjPbboAdnm+yROfE0A@public.gmane.org -- Posted via http://www.ruby-forum.com/.
Hrm - maybe I should just quote my actual code rather than the example. Actually, technically, no - the "hobbies" are NOT shared between people. So two people can''t share the same hobby. Each Person has their own list of hobbies, and one of those is their "favorite" and I dont want to have some "favorite" boolean. My actual code has nothing to do with people and hobbies, this was just a (poor) example. Thanks for the help! Marnen Laibow-Koser wrote:> The Barge wrote: >> I think I''ve just thoroughly confused myself at this point. I have a >> class that has a has_many and has_one relationship that use the same >> object. >> >> Here is an example: >> >> class Person < ActiveRecord::Base >> has_many :hobbies >> has_one :favorite_hobby, :class_name => "Hobby" >> end >> >> class Hobby < ActiveRecord::Base >> belongs_to :person >> belongs_to :person, :foreign_key => "favorite_hobby_id" >> end >> >> Of course, this doesn''t work. Any ideas what I need to change to get >> this to work properly? >> >> Thanks. > > I think you should be using habtm for the hobbies (two people can enjoy > the same hobby, right?) and an additional belongs_to for the favorite. > This may seem counterintuitive, but remember that belongs_to is used on > the table with the foreign key field (which in this case is > people.favorite_hobby_id). So: > > class Person > habtm :hobbies > belongs_to :favorite_hobby, :class_name => ''Hobby'' > end > > class Hobby > habtm :people > # reverse association probably unnecessary for favorite_hobby > end > > Best, > -- > Marnen Laibow-Koser > http://www.marnen.org > marnen-sbuyVjPbboAdnm+yROfE0A@public.gmane.org-- Posted via http://www.ruby-forum.com/.
On Thu, Jul 16, 2009 at 3:57 PM, The Barge <rails-mailing-list-ARtvInVfO7ksV2N9l4h3zg@public.gmane.org> wrote:> > Hrm - maybe I should just quote my actual code rather than the example. > Actually, technically, no - the "hobbies" are NOT shared between people. > So two people can''t share the same hobby. > > Each Person has their own list of hobbies, and one of those is their > "favorite" and I dont want to have some "favorite" boolean. My actual > code has nothing to do with people and hobbies, this was just a (poor) > example. >I''m new so I don''t have the full answer, but without the favorite boolean, behind the scenes I think a table of "HobbyFavorite" would be needed that has person_id and hobby_id, unless I''m missing something. So it sounds like you need two "has_one" relationships defined? both Person and Hobby would have: has_one: favorite_hobby You then could have a FavoriteHobby model object with belongs_to: person belongs_to: hobby I''m not 100% this would work or is a good idea, but nobody else has suggested anything yet, so I''m trying to learn in the process. Take any of the above with a HUGE chunk of salt:) --~--~---------~--~----~------------~-------~--~----~ 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 rubyonrails-talk-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org To unsubscribe from this group, send email to rubyonrails-talk+unsubscribe-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org For more options, visit this group at http://groups.google.com/group/rubyonrails-talk?hl=en -~----------~----~----~----~------~----~------~--~---
Rick wrote: [...]> I''m new so I don''t have the full answer, but without the favorite > boolean, > behind the scenes I think a table of "HobbyFavorite" would be needed > that > has person_id and hobby_id, unless I''m missing something.Since there would be a 1:1 association between Person and HobbyFavorite, that would actually be functionally equivalent to just having a hobby_favorite_id in Person. Best, -- Marnen Laibow-Koser http://www.marnen.org marnen-sbuyVjPbboAdnm+yROfE0A@public.gmane.org -- Posted via http://www.ruby-forum.com/.
Marnen Laibow-Koser wrote:> Rick wrote: > [...] >> I''m new so I don''t have the full answer, but without the favorite >> boolean, >> behind the scenes I think a table of "HobbyFavorite" would be needed >> that >> has person_id and hobby_id, unless I''m missing something. > > Since there would be a 1:1 association between Person and HobbyFavorite, > that would actually be functionally equivalent to just having a > hobby_favorite_id in Person.That is exactly how the database looks. Instead of people and hobbies, my code actually uses Users and Characters. The People/Hobby was just another example. Each user can have any number of characters, but only one character is marked as the "selected character". The users table has a selected_character_id, and the characters table has a user_id. Thanks. -- Posted via http://www.ruby-forum.com/.
The Barge wrote: [...]> That is exactly how the database looks. Instead of people and hobbies, > my code actually uses Users and Characters. The People/Hobby was just > another example. Each user can have any number of characters, but only > one character is marked as the "selected character". > > The users table has a selected_character_id, and the characters table > has a user_id. > > Thanks.OK...then how about class User has_many :characters belongs_to :selected_character, :class_name => ''Character'' end class Character belongs_to :user end ? Best, -- Marnen Laibow-Koser http://www.marnen.org marnen-sbuyVjPbboAdnm+yROfE0A@public.gmane.org -- Posted via http://www.ruby-forum.com/.
> OK...then how about > > class User > has_many :characters > belongs_to :selected_character, :class_name => ''Character'' > end > > class Character > belongs_to :user > endThat did it! I have no idea why my brain tends to reverse the belongs and has relationships sometimes. Thanks a lot for your help. -- Posted via http://www.ruby-forum.com/.
The Barge wrote: [...]> That did it! I have no idea why my brain tends to reverse the belongs > and has relationships sometimes.Well, in this case, the selected_character relationship is backwards from what it "should" be. I wouldn''t have figured that out immediately either. :)> Thanks a lot for your help.You''re welcome. Best, -- Marnen Laibow-Koser http://www.marnen.org marnen-sbuyVjPbboAdnm+yROfE0A@public.gmane.org -- Posted via http://www.ruby-forum.com/.