How to rescue model transaction and show the user an error?

Question

So imagine you have 2 models, Person and Address, and only one address per person can be marked as 'Main'. So if I wanna change a person's main address, I need to use a transaction, to mark the new one as main and unmark the old one. And as far as I know using transactions in controllers is not good so I have a special method in model, thats what I've got:

AddressesController < ApplicationController
 def update
  @new_address = Address.find(params[:id])
  @old_address = Address.find(params[:id2])
  @new_address.exchange_status_with(@old_address)       
 end
end

Model:

class Address < ActiveRecord::Base
  def exchange_status_with(address)
    ActiveRecord::Base.transaction do
     self.save!
     address.save!
    end     
  end
end

So thequestion is, if the transaction in the model method fails, I need to rescue it and notify the user about the error, how do I do that? Is there a way to make this model method return true or false depending on whether the transaction was successful or not, like save method does?

I probably could put that transaction in the controller and render the error message in the rescue part, but I guess its not right or I could put that method in a callback, but imagine there is some reason why I cant do that, whats the alternative?

PS dont pay attention to finding instances with params id and id2, just random thing to show that I have 2 instances

Solution

def exchange_status_with(address)
  ActiveRecord::Base.transaction do
   self.save!
   address.save!
  end
rescue ActiveRecord::RecordInvalid => exception
  # do something with exception here
end

FYI, an exception looks like:

#<ActiveRecord::RecordInvalid: Validation failed: Email can't be blank>

And:

exception.message
# => "Validation failed: Email can't be blank"

Side note, you can change self.save! to save!

---

Alternate solution if you want to keep your active model errors:

class MyCustomErrorClass < StandardError; end

def exchange_status_with(address)
  ActiveRecord::Base.transaction do
   raise MyCustomErrorClass unless self.save
   raise MyCustomErrorClass unless address.save
  end
rescue MyCustomErrorClass
  # here you have to check self.errors OR address.errors
end