From: Robert Klemme <shortcutter@...>
Date: 2010-09-27T19:56:53+09:00
Subject: Re: Need assistance with hash of arrays and injecting values

On Sat, Sep 25, 2010 at 2:29 PM, Alpha Blue <jdezenzio@gmail.com> wrote:
> I'm creating a class that will run a number of tasks based on a start
> and end date.  It only runs between week 4 and week 15 of my current
> system.
>
> A current hash of arrays is defined for the current calendar year the
> tasks run.
>
> @h = {
>  :week_four => ["2010-09-20", "2010-09-26"],
>  :week_five => ["2010-09-27", "2010-10-03"],
>  :week_six => ["2010-10-04", "2010-10-10"],
>  :week_seven => ["2010-10-11", "2010-10-17"],
>  :week_eight => ["2010-10-18", "2010-10-24"],
>  :week_nine => ["2010-10-25", "2010-10-31"],
>  :week_ten => ["2010-11-01", "2010-11-07"],
>  :week_eleven => ["2010-11-08", "2010-11-14"],
>  :week_twelve => ["2010-11-15", "2010-11-21"],
>  :week_thirteen => ["2010-11-22", "2010-11-28"],
>  :week_fourteen => ["2010-11-29", "2010-12-05"],
>  :week_fifteen => ["2010-12-06", "2010-12-12"]
> }

I don't see the point in defining this.  There is class Date which
abstracts dates and allows to do calculations on them.  Also, encoding
something which is numeric (the week number) as text in a Hash key
seems overly awkward.  This makes calculations of the kind "is date x
in week y" overly complicated.

> I want to inject these into a similar task:
>
> @current_week is an instance variable within the class that holds the
> current week (i.e. week 10 for instance so '10')
>
> @weekly_report is defined as an array that will hold the report
> listings.
>
> The VirtualReport.reportlistings method takes two dates - a start date
> and an end date.  I only want them to run up to the current week.  So,
> in this example, if it's week 10, it should run a report for week
> 4,5,6,7,8,9, and 10.  But, it should not run a report for
> 11,12,13,14,15.  Furthermore, it should check to ensure that the data is
> not empty.
>
> for i in 0..(@current_week-4)
>  @weekly_report = VirtualReport.reportlistings("INSERT HASH VALUES")
> end
>
> Where I placed the INSERT HASH VALUES above is where I want to inject my
> values based on the current week.  Therefore, I'm pretty certain the
> hash needs to be ordered or sorted so that they maintain the current
> week layouts.  But, I'm not very good with hashes in general and could
> use some help or a better example of how to accomplish this task.  The
> weekly reports will be stored in an array and used later on in the
> class.
>
> Any help would be appreciated.

I'd start with a proper representation of dates (class Date comes to
mind) and add another one for representing weeks on top of that.  So
you could do

# untested
Week = Struct.new :start_date do
  def initialize(date)
    self.start_date = find_start_date(date)
  end

  def in_week?(date)
    (start_date ... (start_date + 7)).include? date
  end

  def week_of_year
    first = find_start_date(Date.new(start_date.year, 1, 1))
    (start_date - first) / 7 + 1
  end

  include Comparable

  def <=>(week)
    star_date <=> week.start_date
  end

  def succ
    self.class.new(start_date + 7)
  end

  def pred
    self.class.new(start_date - 7)
  end

private
  def find_start_date(date)
    until date.monday? # or whatever should start your week
      date = date.prev_day
    end
    date
  end
end

Then base your other data structures on these primitive types.

Kind regards

robert

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