Question

I also have a week number, extracted from another time object like this

other_time.strftime('%W').to_i

%W gives:

Week number of the year. The week starts with Monday. (00..53)

I also have a day name:

'Tuesday'

How can I build a DateTime object that represents Tuesday in the week indicated by the week number? The time component of the object is irrelevant at this stage, as it will be changed in a later step.

I’m using Rails 3.2.0 and Ruby 1.9.2p320.

Edit: Incorrectly stated that I wanted a Time object. I actually want a DateTime object.

Answer 1

You can check the day against your desired day, and adjust accordingly. It’s not great, but it does work.

$ irb
1.9.3p0 :001 > require 'date'
 => true 
1.9.3p0 :002 > other_date = DateTime.now
 => #<DateTime: 2012-06-08T14:23:44-04:00 ((2456087j,66224s,205565000n),-14400s,2299161j)> 
1.9.3p0 :003 > week = other_date.strftime('%W').to_i
 => 23 
1.9.3p0 :004 > target_day = 2 # Tuesday
 => 2 
1.9.3p0 :005 > while other_date.wday > target_day ; other_date = other_date.prev_day ; end
 => nil 
1.9.3p0 :006 > while other_date.wday < target_day ; other_date = other_date.next_day ; end
 => nil 
1.9.3p0 :007 > other_date # Tuesday of this week
 => #<DateTime: 2012-06-05T14:23:44-04:00 ((2456084j,66224s,205565000n),-14400s,2299161j)> 
1.9.3p0 :008 > other_date.strftime('%W').to_i == week
 => true