Ruby on Rails: Use a datetime instead of a boolean database field

The problem

When tracking whether an action has occurred, it’s tempting to use a boolean field. I had the task of tracking if a phone number has been sent to a user(based on some logic that doesn’t matter right now) and I chose the boolean route:

t.boolean "is_phone_number_sent_to_user", default: false

This works, but you lose valuable information: when did it happen? This timestamp is often useful for debugging, analytics, or business logic later on.

The solution

Instead of using a boolean, use a datetime field. If the field is nil, the action hasn’t happened yet. If it has a value, the action occurred at that time:

t.datetime "phone_number_sent_to_user_at"

Here’s how you’d use it in your Rails model:

class User < ApplicationRecord
  def phone_number_sent_to_user?
    phone_number_sent_to_user_at.present?
  end

  def send_phone_number_to_user
    # Your logic to send the phone number
    update(phone_number_sent_to_user_at: Time.current)
  end
end

Now you can check if it was sent (user.phone_number_sent_to_user?) and also know exactly when it happened (user.phone_number_sent_to_user_at). The storage cost is minimal, and you get valuable timestamp data almost for free.

Conclusion

Using datetime instead of boolean gives you the same functionality (checking if something happened) plus the added benefit of knowing when it happened. It’s almost free in terms of storage, and you’ll thank yourself later when you need that timestamp information.