CODEWITHSUNDEEP
ruby-on-rails-3postgresqltransactionsdatamapper
Gerard
Gerard

Reputation: 4848

Transactions in Datamapper & Rails (dm-rails)

I have two models: hotel and location. A location belongs to a hotel, a hotel has one location. I'm trying to create both in a single form, bear in mind that I can't use dm-nested for nested forms due to a dependency clash.

I have code that looks like:

if (@hotel.save && @location.save)
  # process
else
  # back to form with errors
end

Unfortunately, @hotel.save can fail and @location.save can complete (which confuses me because I didn't think the second condition would run in an AND block if the first one failed).

I'd like to wrap these in a transaction so I can rollback the Location save. I can't seem to find a way to do it online. I'm using dm-rails, rails 3 and a postgresql database. Thanks.

Upvotes: 0

Views: 181

Answers (1)

Adiel Mittmann
Adiel Mittmann

Reputation: 1764

The usual way to wrap database operations in DataMapper is to do something like this:

@hotel.transaction do
  @hotel.save
  @location.save
end

Notice that @hotel is quite arbitrary there; it could as well be @location or even a model name like Hotel.

In my experience, this works best when you enable exceptions to be thrown. Then if @hotel.save fails, it will throw an exception, which will be caught by the transaction block, causing the transaction to be rolled back. The exception is, of course, reraised.

Upvotes: 1

Related Questions