Update Cardinals By delta for Postgresql.

A gem to more safely update cardinal numbers like credits.

It will

• start a transaction
• make the change with a delta attr = attr + #{attributes[attr]}}
• call the given block with an indifferent hash of the latest values in the db.
• update the given attributes on the instance to the latest values.
• end transaction.

If any exceptions are thrown in the block, the change will automatically be reverted.

Sql will be like:

  update accounts set credits = credit + -20 where id = 6 returning credits

gem 'update_cardinals_by', '~> 0.1.0'

update_cardinals_by!(credits: -20) do |res|
  fail 'not enough credits' if res[:credits] < 0
  CreateWantedItems.run(..)
  CreditMutation.create credits_new: res[:credits],
                        credits_old: credits,
                        credits_change: -20
end

0.3.0 changed activerecord support to 6.1 and 7.0

0.2.0 changed activerecord support to 5.2 and 6.0

0.1.0 changed activerecord support from 4.2 to 5.0 and 5.1

rake setup
rake db:setup
bundle exec appraisal install
bundle exec appraisal rspec