What's the correct way to handle optional time information in Rails?

Question

I'm working on a Rails application that allows users to define Tasks, which require a due_date. The due_date may or may not include a time.

The way we're handling this right now feels like a hack. due_dates default to 12:00 AM, and in that case we don't display a time. The DateTime object doesn't allow for empty Time values as far as I know.

Should I split this information up into two columns in the database? How do you guys handle this?

Answer 1

Splitting the attributes may be unnecessarily complex. Why not adopt a convention that if no time is specified then default it to midnight or noon on the date in question? Unless you need to be able to distinguish between the two cases, i.e. this is midnight because it was explicitly specified or this is midnight because no time was specified. If the latter then splitting them might be advisable or just add a boolean to disambiguate the cases.

If you thought you had further use for a separated date and time and would expend lots of energy splitting a single field for other reasons then that might also argue for splitting.

Answer 2

Since your data structure needs to accommodate dates with and without a time, you have two choices:

Use a Ruby DateTime object with a flag value for the time to indicate that the date does not have a time. The usual flag value for this is 0 which then means the midnight time can't be shown. (Midnight is 0 seconds after the day has started.)

For example, parsing "Jan 1, 2010" into a DateTime will give you Jan 1, 2010 00:00.

Otherwise you'll need to invent your own data structure. Easiest would probably a Class with a DateTime and a "show_time" boolean flag. -- by using a DateTime to hold the time, you'll be able to use the DateTime output methods, and do arithmetic with them if needed.

Creating a new data structure is not such a big deal in Ruby, but if you can live without tasks due exactly at midnight, I'd recommend method 1. Note that you'd probably want to print them without a time since that's what the task definer requested. Or you could include "(any time)" in the output.

PS

Watch out for timezones! Many ways to handle, but you should be sure to choose one deliberately.