Can I use Ruby's map method with a kind of case statement to build an intelligent array?

Question

Here is the way I've written my code:

sevendas = sixdas = fivedas = fourdas = threedas = twodas = onedas = todays = 0
@sat = List.all({:company_id => params[:id], :sat => true, :created_at => {:$gte => (time - 1.week)}})
@sat.each do |s|       
    if s["created_at"].strftime("%m-%d-%Y") == (time-1.week).strftime("%m-%d-%Y")
        sevendas += 1
    elsif s["created_at"].strftime("%m-%d-%Y") == (time-6.days).strftime("%m-%d-%Y")
        sixdas += 1
    elsif s["created_at"].strftime("%m-%d-%Y") == (time-5.days).strftime("%m-%d-%Y")
        fivedas += 1
    elsif s["created_at"].strftime("%m-%d-%Y") == (time-4.days).strftime("%m-%d-%Y")
        fourdas += 1
    elsif s["created_at"].strftime("%m-%d-%Y") == (time-3.days).strftime("%m-%d-%Y")
        threedas += 1
    elsif s["created_at"].strftime("%m-%d-%Y") == (time-2.days).strftime("%m-%d-%Y")
        twodas += 1
    elsif s["created_at"].strftime("%m-%d-%Y") == (time-1.day).strftime("%m-%d-%Y")
        onedas += 1
    elsif s["created_at"].strftime("%m-%d-%Y") == (time).strftime("%m-%d-%Y")
        todays += 1
    end
end
@tot_sat = []
@tot_sat.push( sevendas, sixdas, fivedas, fourdas, threedas, twodas, onedas, todays )

This works fine. What I'm working on now is improving my code and learning more efficient ways at writing these types of blocks.

I'm figuring that I can possibly use map here - it's the method of the day for me, trying to get a better handle on it.

Answer 1

@tot_sat = @sat.group_by do |s|
  (time - s["created_at"]).to_i / 1.day
end.select do |diff, _| 
  diff < 8 
end.sort_by do |diff, _| 
  - diff 
end.map do |_, entries| 
  entries.count 
end

This solution groups the entries by the number of days difference from time, and then counts how many entries are in each day difference.

---

Update
The code above has a problem if not all the values (0-7) have entries. In this case, the array will be shorter. To avoid that, we'll use a different tactic in translating the grouped hash into the array:

grouped_sat = @sat.group_by do |s|
  (time - s["created_at"]).to_i / 1.day
end

@tot_sat = (0..7).map { |days| (grouped_sat[days] || []).count }

In this tactic, all values between 0 and 7, in turn, count the number of elements with the queried interval, defaulting at 0 (the length of the empty array), in the case there were no elements with the queried interval.

Answer 2

If you want to compare timestamps by date, use to_date. Without knowing anything else about the context of your code, it can be dramatically cleaned up just by computing s['created_at'].to_date once, and using a case statement:

sevendas = sixdas = fivedas = fourdas = threedas = twodas = onedas = todays = 0
@sat = List.all(company_id: params[:id], sat: true, created_at: {$gte: (time - 1.week)}})
today = time.to_date
@sat.each do |s|
  case s['created_at'].to_date
  when today - 1.week then sevendas += 1
  when today - 6.days then sixdas += 1
  when today - 5.days then fivedas += 1
  when today - 4.days then fourdas += 1
  when today - 3.days then threedas += 1
  when today - 2.days then twodas += 1
  when today - 1.day then onedas += 1
  when today then todays += 1
  end
end
@tot_sat = []
@tot_sat.push( sevendas, sixdas, fivedas, fourdas, threedas, twodas, onedas, todays )

You could further refactor it to drop the ugly sevendas = sixdas = fivedas = ... thing and just store the values in an array.