CODEWITHSUNDEEP
ruby-on-railsarraysrubyhash
disastrous-charly
disastrous-charly

Reputation: 1085

Most efficient way to convert a ruby hash with array as keys to one with single values as keys

I'm stuck on what is the best way to re-arrange my ruby hash.

The main goal is to group results from mysql by month and count.

To do it, i make this request: 

@data = Model.find(params[:id])
             .jobs
             .group('year(created_at)')
             .group('month(created_at)')
             .count(:id)

Which gives me:

#=> {[2013, 12]=>9, [2014, 1]=>4, [2014, 3]=>3, 
#    [2014, 4]=>1, [2014, 6]=>1, [2014, 7]=>1, [2014, 10]=>2}

I'm trying to have a cleaner hash or array to convert to json, where the years are not duplicated.

How can I have something workable like {"Year" => [Month,Count value]}? (or other form)

Idea? (I run ruby 2.2)

Upvotes: 2

Views: 118

Answers (3)

Jean Bob
Jean Bob

Reputation: 565

The answer proposed by @mudosobwa might be correct, but because your target is a json file, you may want some 'named' keys. I suggest you this one :

formated_results = @data.group_by{|k, v| k[0]}.collect{|k,v| {year: k, datas: v.collect{|vv| {month: vv.first.last, count: vv.last}}}}
# {:year=>2013, :datas=>[{:month=>12, :count=>9}]}
# {:year=>2014, :datas=>[{:month=>1, :count=>4}, {:month=>3, :count=>3}, {:month=>4, :count=>1}, {:month=>6, :count=>1}, {:month=>7, :count=>1}, {:month=>10, :count=>2}]}

EDIT : An other solution without the group_by method :

formated_results = Hash.new{|h,k| h[k] = []}
@data.each{|k,v| formated_results[k[0]] << {month: k[1], count: v}}
formated_results = formated_results.collect{|k, v| {year: k, datas: v}}
# {:year=>2013, :datas=>[{:month=>12, :count=>9}]}
# {:year=>2014, :datas=>[{:month=>1, :count=>4}, {:month=>3, :count=>3}, {:month=>4, :count=>1}, {:month=>6, :count=>1}, {:month=>7, :count=>1}, {:month=>10, :count=>2}]}

Then you just have to

formated_results.to_json

The json result shall be :

[
  {
    "year": 2013,
    "datas": [
      { "month": 12, "count": 9 }
    ]
  },
  {
    "year": 2014,
    "datas": [
      { "month": 1, "count": 4 },
      { "month": 3, "count": 3 },
      { "month": 4, "count": 1 },
      { "month": 6, "count": 1 },
      { "month": 7, "count": 1 },
      { "month": 10, "count": 2 }
    ]
  }
]

Upvotes: 4

Aleksei Matiushkin
Aleksei Matiushkin

Reputation: 121000

Given you already have your hash in @data, you might:

@data.inject({}) do |memo, ((y, m), cnt)| 
  (memo[y] ||= {})[m] =  cnt
  memo
end
#⇒ { 
#    2013 => {12 => 9}, 
#    2014 => {1 => 4, 10 => 2, 3 => 3, 4 => 1, 6 => 1, 7 => 1}
#  }

As it was noted by @Surya in comments, it should be hash Year => Hash[Month, Count]. While you still want to have arrays of Month, Count:

@data.inject({}) do |memo, ((y, m), cnt)| 
  memo[y] ||= []
  memo[y] << [m,  cnt]
  memo
end

To json:

require 'json'
result.to_json
#=> "{\"2013\":{\"12\":9},\"2014\":{\"1\":4,\"3\":3,\"4\":1,\"6\":1,\"7\":1,\"10\":2}}"

Upvotes: 2

Axel Tetzlaff
Axel Tetzlaff

Reputation: 1364

@data.to_a.group_by{|ym, c| ym.first }.map{|year, months| [year,months.map{|m,cnt| [m.last, cnt] }] }.to_h
=> {2013=>[[12, 9]], 2014=>[[1, 4], [3, 3], [4, 1], [6, 1], [7, 1], [10, 2]]}

Upvotes: -1

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