Change a hash into an array

Question

I have an Rails 4 application that collects attendance at church services. Some weeks there are two services and some weeks there is only one. I need to get the total attendance for each week and show it as a graph.

By calling:

Stat.calculate(:sum, :attendance, group: :date)

in the console I have been able to collect the data in a hash like this:

{Sun, 06 Jan 2013=>66, Sun, 13 Jan 2013=>65, Sun, 20 Jan 2013=>60, Sun, 27 Jan 2013=>67, Sun, 03 Feb 2013=>60, Sun, 10 Feb 2013=>76, Sun, 17 Feb 2013=>65, Sun, 24 Feb 2013=>52, Sun, 03 Mar 2013=>52, Sun, 10 Mar 2013=>45, Sun, 17 Mar 2013=>56, Sun, 24 Mar 2013=>134, Sun, 31 Mar 2013=>76, Sun, 07 Apr 2013=>88, Sun, 14 Apr 2013=>87, Sun, 28 Apr 2013=>93, Sun, 05 May 2013=>93, Sun, 12 May 2013=>95, Sun, 19 May 2013=>90, Sun, 26 May 2013=>87, Sun, 02 Jun 2013=>71, Sun, 09 Jun 2013=>86, Sun, 16 Jun 2013=>109, Sun, 23 Jun 2013=>80, Sun, 30 Jun 2013=>68, Sun, 07 Jul 2013=>75, Sun, 14 Jul 2013=>73}

But What I need for my chart is an array of hashes in the form of:

{date: "Sun, 23 Jun 2013", attendance: 80}, {date: "Sun, 30 Jun 2013", attendance: 68"}

So I am trying to figure out how to convert the first form into the second form.

I'm sure its something pretty easy, but my limited rails knowledge is hitting a wall.

Shawn Balestracci · Accepted Answer · 2013-07-20 20:38:16Z

5

.collect{|key,value| {:date => key, :attendance => value} }

loop through and create a new hash where the original key becomes the value for date and the original value becomes the value for attendance. These new hashes are collected into an array.

answered Jul 20, 2013 at 20:38

Shawn Balestracci

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1 Comment

Dave Olson Over a year ago

I agree. I used the first answer prior to seeing Shawn's response. I've refactored to this.

Arup Rakshit · Accepted Answer · 2013-07-20 20:55:40Z

2

You can think as below:

h = {"Sun, 06 Jan 2013"=>66, "Sun, 13 Jan 2013"=>65, "Sun, 20 Jan 2013"=>60 }
h.map{|k,v| Hash[:date,k,:attend,v]}
# => [{:date=>"Sun, 06 Jan 2013", :attend=>66},
#     {:date=>"Sun, 13 Jan 2013", :attend=>65},
#     {:date=>"Sun, 20 Jan 2013", :attend=>60}]

edited Jul 20, 2013 at 20:55

answered Jul 20, 2013 at 20:30

Arup Rakshit

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3 Comments

Arup Rakshit Over a year ago

@NielsB. made it readble... :) Ready for all challenges.. :)))

Niels B. Over a year ago

That is better, but I still prefers Shawns answer because it reads well and only requires you to know the collect/map method. Your example also requires you to know the counter intuitive [] class method from the Hash class.

Arup Rakshit Over a year ago

@NielsB. I have no issue... I liked my one, I use Kernel#Hash instead of {}.. simple.. :))) But thanks for throwing your comment.. :) I like feedbacks...

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