Solidify wrote: > Hi everyone, I have a simple question: > > an author has a place of birth and a place of death. Both places > should come from the same table (cities). This should be a > many_to_many relationship, because one author may be born in the same > city where the other author dies.
That's not a good spot for a many-to-many relationship. Rather, it's better modeled as two one-to-many relationships, where an author belongs to one city as birthplace and one city as "deathplace". Since the place of birth and the place of death are semantically different, they should not be shoved into the same association. A better candidate for a many-to-many relationship would be a list of places where an author resided throughout his life. Since they're semantically the same, it makes sense to do many-to-many here. > > Now in the authors-table, one city_id would not be enough, it has to > be two fields, one for birth, one for death. but then, the > @author.city would not work anymore. Could anyone give me a hint how > to solve this? @author.city is semantically meaningless. It *shouldn't* be defined from what you've said. You probably want something like (untested): class Author < AR::B belongs_to :birth_city, :class_name => 'City' belongs_to :death_city, :class_name => 'City' end class City < AR::B has_many :authors_born, :class_name => 'Author', :foreign_key => :birth_city_id has_many :authors_died, :class_name => 'Author', :foreign_key => :death_city_id end Then you can use @author.birth_city and @author.death_city. Does that help? Best, -- Marnen Laibow-Koser http://www.marnen.org mar...@marnen.org -- 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 rubyonrails-t...@googlegroups.com. To unsubscribe from this group, send email to rubyonrails-talk+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/rubyonrails-talk?hl=en.
