http://rails.rubyonrails.org/classes/ActiveSupport/CoreExtensions/Time/Calculations.html#M000231
This might help for calculating days ago:
C:\WINDOWS>irb irb(main):001:0> require 'date' => true irb(main):002:0> t = Date.today => #<Date: 4908063/2,0,2299161> irb(main):004:0> puts t 2006-10-23 => nil irb(main):005:0> puts t - 7 2006-10-16 => nil irb(main):006:0>
I think you can just use the << or >> as in:
irb(main):001:0> require "Date" => true irb(main):002:0> d = Date.new(1997, 12, 31) => #<Date: 4901627/2,0,2299161> irb(main):003:0> d.to_s => "1997-12-31" irb(main):004:0> d2 = d >> 1 => #<Date: 4901689/2,0,2299161> irb(main):005:0> d2.to_s => "1998-01-31" irb(main):006:0> d2 = d >> 2 => #<Date: 4901745/2,0,2299161> irb(main):007:0> d2.to_s => "1998-02-28" irb(main):008:0> d2 = d << 1 => #<Date: 4901565/2,0,2299161> irb(main):009:0> d2.to_s => "1997-11-30" irb(main):010:0>
And I think Date is already included in Rails controllers so you don't need to do the include.
http://rails.rubyonrails.org/classes/ActiveSupport/CoreExtensions/Time/Calculations.html#M000231
@time.advance :months => 7
@time.advance :days => -15
Chet wrote:
Frederick Cheung wrote: > days_ago and weeks_ago aren't there because they are easy: days_ago is > just n * 86400 seconds ago, so you can just write 3.days.ago > months_ago is more complicated because of the varying numbers of day in > a month, you need to now what the value of now is, which is why we have > months_ago, months_since > > A word of warning about Date, Date can be quite slow compared to Time. > Most of the time you won't care, but I was writing a calendaring style > app that did a lot of that sort of calculations and using profiling > showed that the various Date operations were a big slowdown > > Fred
Can someone elaborate on the Date Vs Time speed comment?
I am about to write a lot of calendar like functionality that doesn't really need hour/minute level details and was thinking using Date throughout. But if it means taking a performance hit, I will reconsider.
Thanks.
-- Posted via http://www.ruby-forum.com/.
Simply put, Time values are stored as a long integer and all math on them is done by adding or subtracting two values. This is very fast. Date does a bunch of processing to make sure things work fine, which is slower.
BTW...
require 'rubygems' require 'ruby-units' (gem for unit conversions and unit math) require 'chronic' (interprets natural language time specs) '2 weeks'.from 'today'
#=> Mon Nov 06 17:00:00 EST 2006
'2 weeks'.from 'today'.to_date
=> 2006-11-06
also does... 'ago', 'from', 'until', etc...
but ruby-units doesn't do months since they aren't a fixed size interval. It does contain a number of helpers for converting back and forth between time and date objects, and it will automatically convert to a date object if any math you do takes you outside the normal range for a Time object.
for more about ruby-units see http://www.sciwerks.com/blog/2006/10/06/ruby-units-033/
_Kevin
