I have an active record association that when I delete the parent
object the ::dependent => :nullify option works correctly and sets
the FKs to nil in the join table. Is there a way to make this happen
when the record is updated too? When I remove an association from
the parent, the association is deleted instead of setting the FK to
To complicate things there are times when I would like the behavior to
be :dependent => :destroy_all (depending on what is in the join
I am using has_many :through and depending on what is in my join table
I may want to destroy instead of nullify.
Is this a job for an observer on the join table or maybe overriding
the destroy method :-\
Fabricated Example (i need a better example)
Lets say there is a company that manages shooting locations for
movies. The company offers 2 types of contracts (transferable and
class Movie < ActiveRecord::Base
has_many :contracts, :dependent => :nullify
has_many :locations, :through => :contracts
class Contract < ActiveRecord::Base
belongs_to :location # location_id is unique.
There is a contract type. fixed or transferable
transferrable contracts can have a nil movie. A fixed one can not
class Location < ActiveRecord::Base
has_many :movies, :through => :contracts
A movie may purchase several locations (contracts). If the movie is
canceled, the locations are freed up (if using :dependent
=> :destroy_all), If any locations are changed the unreferenced
locations are deleted. This all works fine.
But what if I have a contract that allows me to transfer a location I
purchased to another movie. If my contract_type is transferable and I
delete the movie the contract should remain but not reference any
movie until I reassign it (dependent => :nullify). The contract
should also remain if I remove just 1 location from my movie and I
want to transfer it to another movie at a later point.