records.rb

def set_deleted_at(value)                                                        
  return self unless is_permanent?                                               
  record = self.class                                                            
  record = record.unscoped if active_record_3?                                   
  record = record.find(id)                                                       
  record.deleted_at = value                                                      
  begin                                                                          
    # we call save! instead of update_attribute so an ActiveRecord::RecordInvalid
    # error will be raised if the record isn't valid. (This prevents reviving records that
    # disregard validation constraints,)                                         
    # run validations when trying to revive a record                             
    value == nil ? record.save! : record.save!(:validate => false)            
    @attributes, @attributes_cache = record.attributes, record.attributes        
  rescue Exception => e                                                          
    # trigger dependent record destruction (they were revived before this record,
    # which cannot be revived due to validations)                                
    record.destroy                                                               
    raise e                                                                      
  end                                                                            
end