create a range of months between two dates in ruby

Question

I need to create logfiles per month for a range of months. Therefor I need all [year,month] tuples in a given range

How do you do iterating over dates?

How can this be done if I'd need to iterate every day?

Answer 1

For example:

((Date.today - 90)..Date.today).map{|d| [d.year, d.month]}.uniq
#=> [[2012, 12], [2013, 1], [2013, 2], [2013, 3]]

Answer 2

  start_date = 1.year.ago.to_date
  end_date = Date.current.yesterday
  monthly = [Date.new(start_date.year, start_date.beginning_of_month.month, 1)]
  (start_date..end_date).each do |d|
    month_date = Date.new(d.year, d.next_month.beginning_of_month.month, 1)
    monthly << month_date if monthly.exclude?(month_date) && month_date < end_date - 1.month
  end
  monthly

=> [Fri, 01 Sep 2017, Sun, 01 Oct 2017, Wed, 01 Nov 2017, Fri, 01 Dec 2017, Sun, 01 Jan 2017, Thu, 01 Feb 2018, Thu, 01 Mar 2018, Sun, 01 Apr 2018, Tue, 01 May 2018, Fri, 01 Jun 2018, Sun, 01 Jul 2018, Wed, 01 Aug 2018]

Answer 3

Ruby Date supports producing successive days and offers a next_month method which could be used to efficiently iterate over months.

Here's a generic method that adapts to the precision of your inputs:

require 'date'

def date_tuples(from,to)
  prec   = from.size
  start  = Date.new(*from)
  finish = Date.new(*to)

  filter_on = [:day,:mon].first(3-prec)
  filter = ->(d) { filter_on.all? {|attr| d.send(attr) == 1 } }

  (start..finish)
    .select(&filter)
    .map { |d| [d.year,d.mon,d.day].first(prec) }
end

[7] pry(main)> date_tuples([2012],[2015])
=> [[2012], [2013], [2014], [2015]]
[8] pry(main)> date_tuples([2012,10],[2013,3])
=> [[2012, 10], [2012, 11], [2012, 12], [2013, 1], [2013, 2], [2013, 3]]
[9] pry(main)> date_tuples([2012,10,25],[2012,11,6])
=> [[2012, 10, 25],
 [2012, 10, 26],
 [2012, 10, 27],
 [2012, 10, 28],
 [2012, 10, 29],
 [2012, 10, 30],
 [2012, 10, 31],
 [2012, 11, 1],
 [2012, 11, 2],
 [2012, 11, 3],
 [2012, 11, 4],
 [2012, 11, 5],
 [2012, 11, 6]]

Answer 4

I came up with this solution to generate a list of all [year,month] tuples in the range:

first=[2012,10]
last=[2013,03]
(first[0]..last[0]).to_a.product((1..12).to_a).select{|ym|(first..last).cover?(ym)}
=> [[2012, 10], [2012, 11], [2012, 12], [2013, 1], [2013, 2], [2013, 3]]