Conditional insertions to hbtm join tables.

rubyonrails-talk
1

Is there anyway I can prevent the collection<<(object, ...) and similar methods from adding objects that do not satisfy a specific condition. This would be similar to the :condition option on the has_and_belongs_to_many association.

I want to somehow place a condition or rewrite collection<<(object, ...) and similar methods so that when an "incompatible" object is attempted to be added to the collection, it returns false or throws an exception. Is this possible?

Thanks!

2

Sounds like you want validates_associated.

http://api.rubyonrails.com/classes/ActiveRecord/Validations/ClassMethods.html#M001334

3

It was a condition relating the record with the association and the associated record.

I ended up using the :before_add option and raising an exception (which rolls back the transaction).

Thanks!