Set a model attribute in the background, based on another attribute?

Question

I have an Auction model with several attributes, two of which are current_auction:boolean and scheduled_start:datetime. How can I make the boolean (false by default) become true when the scheduled_start becomes the current time? Please tell me if you need more information. I'm assuming that I will need to use script/runner, but have no experience with it.

Answer 1

I wouldn't store the current_auction as a property. Current_auction is rather a state that depends on the scheduled_start time vs. the current time. Don't put it in the database, but rather add it as a method on your model that compares the scheduled_start with the current time and returns true/false based on the calculation.

If you need to select based on whether it is current or not, use selection logic that depends on the scheduled_start time rather than current/not current.

Answer 2

Mostly likely, you don't want it in the database at all as tvanfosson says.

But if you need it in the database (say you need to search it with Sphinx) you would probably want a database trigger. See MySQL 5.0 Reference Maunual for some information (assuming you're using MySQL).

For things that require more complex logic I'd set up a queuing system and add a message on the queue to update that attribute in the after_save hook. That way it would trigger the update, but not actually wait for the update to complete before returning to the user. I had a question on asynchronous queues and I ended up using Starling and Workling.