Tip: Never mix up greater/less than when comparing dates again
When it comes to compare dates, for some reason my brain really struggles. I mix up
>= all the time and end up flipping them.
start_date greater than
end_date? Or vice-versa? I get confused because I think about dates in terms of
Luckily, Rails is here to save the day and make sure I never make this mistake again by adding
after? for all Date-related comparisons.
start_date = Date.new(2019, 3, 31) end_date = Date.new(2019, 4, 1) start_date.before? end_date #=> true end_date.after? start_date #=> true start_date = Date.new(2020, 8, 11) end_date = Date.new(2018, 8, 11) start_date.before? end_date #=> false
I find myself using these methods frequently in Rails model validations when I need to ensure two dates form a valid range.
class Promotion < ApplicationRecord validate :valid_eligiblity_range? def valid_eligiblity_range? return unless expiration_date? && start_date? if !expiration_date.after?(start_date) errors.add(:start_date, "must be before Expiration Date") errors.add(:expiration_date, "must be after Start Date") end end end
Rails API Docs: DateAndTime::Calculations#before?
Rails API Docs: DateAndTime::Calculations#after?