How to prevent ActiveRecord instance destruction

November 21st, 2005

In one of my projects, I wanted to prevent instances of particular classes to be deleted if they were in any way associated to another object. In database terms, I wanted an ON DELETE RESTRICT constraint.

Since I cannot rely on the database to enforce it for me (MySQL 4, MyISAM engine), I coded the following:

I had to override destroy because in has_and_belongs_to_many relationships, Rails deletes join table records before deleting the record. This means that in before_destroy filters, self.contacts.empty? will always report true. Ticket #1183: dependents are destroyed before client before_destroy hooks are called is already opened on this issue.

UPDATE (2006-03-08)* Fixed since 2006-02-13

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I am François Beausoleil, a Ruby on Rails coder. During the day, I work on XLsuite. At night, I am interested many things. Read my biography

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