Date comparison in Rails 3.2

Question

Stage:

I have this model:

Promo(id: integer, start_date: datetime, end_date: datetime)

I want to know which current promotions. May be our query should be like:

SELECT * FROM promos WHERE now BETWEEN start_date AND end_date;

Question:

How should I make it in Ruby? Which is the correct way?

Thank you.

Answer 1

Yes, you can use comparison operators to compare dates e.g.:

irb(main):018:0> yesterday = Date.new(2009,6,13)
=> #<Date: 4909991/2,0,2299161>
irb(main):019:0> Date.today > yesterday
=> true

But are you trying to compare a date to a datetime?

If that's the case, you'll want to convert the datetime to a date then do the comparison.

or

Date.parse('2010-11-01') < Date.today

will return true if '2010-11-01' has already passed

I hope this helps.

Answer 2

Haven't tested this, but try something like:

currentTime = Time.now()
Promo.find(
     :all,
     :conditions => ['start_date < ? AND end_date > ?', currentTime, currentTime]
)

You might need to use the Date class if the Time class doesn't work

Answer 3

Rails is intelligent. If you retrieve a date/time, it will converted to DateTime object. On contrary, passing DateTime object to the where clause (for Rails 3.x), it will correctly build the where clause.

String passed to where clause will be passed to the SQL where clause. If you pass an array, second and later elements will be replaced with '?' character in the first element.

So, for your case:

Promo.where(["? between start_date and end_date", DateTime.now])

works. I verified on my Rails model(Position) which happen to have start_date and end_date, and works correctly:

[1] pry(main)> Position.where(["? between start_date and end_date", DateTime.now]).count
=> 2914

It's on Rails 3.2.8 with PostgreSQL.