How to extract values from hashes into separate arrays?

Question

How can i change this:

array_of_hash = [{"month"=>"January", "count"=>67241},
                 {"month"=>"February", "count"=>60464},
                 {"month"=>"March", "count"=>30403}] 

To this :

month = ["January", "February", "March"]
count = [67241, 60464,30403]

Answer 1

To extract a single value (eg 'month' ), you could use map :

array_of_hash.map { |hash| hash['month'] }
#=> ["January", "February", "March"]

Which can be extended to return the values for both, 'month and 'count' :

array_of_hash.map { |h| [h['month'], h['count']] }
#=> [["January", 67241], ["February", 60464], ["March", 30403]]

There's also a method to fetch multiple values at once – values_at :

array_of_hash.map { |h| h.values_at('month', 'count') }
#=> [["January", 67241], ["February", 60464], ["March", 30403]]

The resulting array can then be rearranged via transpose :

array_of_hash.map { |h| h.values_at('month', 'count') }.transpose
#=> [["January", "February", "March"], [67241, 60464, 30403]]

The two inner arrays can be assigned to separate variables using Ruby's array decomposition :

months, counts = array_of_hash.map { |h| h.values_at('month', 'count') }.transpose

months #=> ["January", "February", "March"]
counts #=> [67241, 60464, 30403]

Answer 2

A simple solution is to iterate the array of hashes and add the required values to two separate arrays:

months = []
counts = []
array_of_hash.each do |hash|
  months << hash["month"]
  counts << hash["count"]
end

But you could also use each_with_object

months, count = array_of_hash.each_with_object([[], []]) do |hash, accu|
  accu[0] << hash["month"]
  accu[1] << hash["count"]
end

or iterate twice and get the months and counts separately:

months = array_of_hash.map { |hash| hash["month"] }
counts = array_of_hash.map { |hash| hash["count"] }

Answer 3

months, counts =
  array_of_hash.
    flat_map(&:values).
    partition(&String.method(:===))

---

months, counts =
  %w|month count|.map { |key| array_of_hash.map { |h| h[key] } }

Answer 4

month = []
count = []
array_of_hash.each do |hash|
   month << hash['month']
   count << hash['count']
end