Hi, I was wondering if there was any way to include runtime parameters in the :conditions clause of a has_many relationship?
I'm trying to model the concept of a person who goes by various nicknames. My Person model contains a "name" attribute containing their real name, and a "has_many :nicknames" relationship. Through my business rules, I'm enforcing the requirement that a person's real name is always included in the database as a nickname.
(If this seems like a really bad data structure, I'm open to suggestions. However, having weighed up various alternatives, this seems to me to be the least worst solution.)
I now want to add an "alternative_nicknames" relationship, which will comprise all of the person's nicknames *excluding* their real name. I've tried
has_many :alternative_nicknames, :class_name => "Nickname", :conditions => ["nickname <> ?", self.name]
- however, since has_many is a class-level method, the :conditions block is evaluated at the point of loading the class, and therefore self.name returns "Person" rather than the person's name. Out of desperation I've even tried wrapping the has_many declaration in an after_initialize callback, but then it complains that has_many is not defined. The examples in the Rails docs and the Pragmatic book only demonstrate static SQL fragments being used in the :conditions clause, not ones incorporating parameters. Any ideas how I can achieve this?
(If it helps explain things any better, I believe this person's (unanswered) question is equivalent to mine: http://groups.google.com/group/rubyonrails-talk/msg/5006b300e4e5a8cc )
- Matt