It isn't possible to receive result of the STORE part when doing Bucket#cas asynchronously

The callback of the Bucket#cas method is triggered only once, when it fetches old value, and it isn't possible to receive notification if the next store operation was successful:

Couchbase.bucket.run do |c|
c.cas("foo") do |oldval|

1. modify oldval and return newval
   newval
   end
   end

It would be better if cas operation will be more like other operations in async mode and will return Result object twice, first for get part and then for set.