Question

I have code which is updating a model’s property then calling save!. A Rails.logger.info call shows that the model thinks it has the new values. But the SQL write performed by the save! call is writing the old value to the database.

At first it wasn’t writing anything to the database at all when I called save!. I thought it was that the object wasn’t thinking its value had changed for some reason: changed? returned false, so I used a _will_change! notification to force a write. But now it is doing a write, but with the old values.

This doesn’t happen from the “rails console” command line: there I’m able to update the property and it will return changed? of true, and let me save successfully.

Excerpt from the server log follows. Note that the object thinks it has log_ids of ‘1234,5678,1137’, but writes to the database ‘1234,5678’.

current log ids are [1234, 5678]
new log ids are [1234, 5678, 1137]; writing log_ids of ‘1234,5678,1137’ to NewsList 13 with dirty true
SQL (2.0ms) UPDATE “news_lists” SET “log_ids” = ‘1234,5678’, “updated_at” = ‘2012-01-02 02:12:17.612283’ WHERE (“news_lists”.”id” = 13)

The object property in question is log_ids, which is a string containing several IDs of another kind of object.

The source code that produced the output above:

def add_log(new_log)
  new_ids = get_log_ids
  Rails.logger.info("current log ids are #{new_ids}")
  if new_ids.length >= NewsList.MAX_LENGTH
    new_ids.shift
  end
  log_ids_will_change!
  new_ids.push new_log.id
  log_ids = new_ids.join ","
  Rails.logger.info("new log ids are #{new_ids}; writing log_ids of '#{log_ids}' to NewsList #{id} with dirty #{changed?}")
  save!
end
def get_log_ids
  if log_ids 
    log_ids.split(",").map &:to_i 
  else
    []
  end
end

Can anyone suggest what might be going on here?

Answer 1

Add the self to self.log_ids = new_ids.join "," otherwise you will just be assigning to the local variable (namesake) instead of the db-persisted attribute (column).