From: Stefan Rusterholz <apeiros@...>
Date: 2007-08-19T16:58:46+09:00
Subject: Re: splitting Array - DRY

Josselin wrote:
> I am presently splitting an array on 4 successives periods of time , is
> there a DRYest way to do it, or that's the way to go ?  thanks
> 
>       @ads_id_w1 = advertisings.map {|ad| ad.id if ((ad.valid_until -
> ad.created_at) / 86400.0 <= 7)}.compact
> 
>       @ads_id_w2 = advertisings.map {|ad| ad.id if (((ad.valid_until -
> ad.created_at) / 86400.0 > 7) && ((ad.valid_until - ad.created_at) /
> 86400.0 <= 14)) }.compact
> 
>       @ads_id_w3 = advertisings.map {|ad| ad.id if (((ad.valid_until -
> ad.created_at) / 86400.0 > 14) && ((ad.valid_until - ad.created_at) /
> 86400.0 <= 21)) }.compact
> 
>       @ads_id_w4 = advertisings.map {|ad| ad.id if (((ad.valid_until -
> ad.created_at) / 86400.0 > 21) && ((ad.valid_until - ad.created_at) /
> 86400.0 <= 31)) }.compact

class ClassOfAd
  def week # may want to name it differently
    return nil unless whateverdate.between?(acceptable_start, 
acceptable_end) # your call here
    ((ad.valid_until - ad.created_at).div(604800)) % 4
end
@ads_id = Array.new(4) { [] }
advertisings.each {|ad| @ads_id[ad.week] = ad.id if ad.week }

Depending on your needs that code can be condensed a bit more.

Regards
Stefan
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