Create a new array from existing hash based on a keys value - ruby

Question

[{"date"=>"2020-09-15", "work_category"=>"CASE PICKS", "count"=>"21315"},
{"date"=>"2020-09-15", "work_category"=>"LOADING", "count"=>"6401"},
{"date"=>"2020-09-15", "work_category"=>"PALLET STAGING", "count"=>"6649"},
{"date"=>"2020-09-15", "work_category"=>"PUTAWAY", "count"=>"4974"},
{"date"=>"2020-09-15", "work_category"=>"RECEIVING", "count"=>"4108"},
{"date"=>"2020-09-16", "work_category"=>"CASE PICKS", "count"=>"16842"},
{"date"=>"2020-09-16", "work_category"=>"LOADING", "count"=>"4987"},
{"date"=>"2020-09-16", "work_category"=>"PALLET STAGING", "count"=>"5716"},
{"date"=>"2020-09-16", "work_category"=>"PUTAWAY", "count"=>"6292"},
{"date"=>"2020-09-16", "work_category"=>"RECEIVING", "count"=>"4894"},
{"date"=>"2020-09-17", "work_category"=>"CASE PICKS", "count"=>"24849"},
{"date"=>"2020-09-17", "work_category"=>"LOADING", "count"=>"5303"},
{"date"=>"2020-09-17", "work_category"=>"PALLET STAGING", "count"=>"5753"},
{"date"=>"2020-09-17", "work_category"=>"PUTAWAY", "count"=>"5136"},
{"date"=>"2020-09-17", "work_category"=>"RECEIVING", "count"=>"4699"},
{"date"=>"2020-09-18", "work_category"=>"CASE PICKS", "count"=>"11806"},
{"date"=>"2020-09-18", "work_category"=>"LOADING", "count"=>"5147"},
{"date"=>"2020-09-18", "work_category"=>"PALLET STAGING", "count"=>"5426"},
{"date"=>"2020-09-18", "work_category"=>"PUTAWAY", "count"=>"5110"},
{"date"=>"2020-09-18", "work_category"=>"RECEIVING", "count"=>"4534"},
{"date"=>"2020-09-19", "work_category"=>"CASE PICKS", "count"=>"8086"},
{"date"=>"2020-09-19", "work_category"=>"LOADING", "count"=>"1753"},
{"date"=>"2020-09-19", "work_category"=>"PALLET STAGING", "count"=>"2201"},
{"date"=>"2020-09-19", "work_category"=>"PUTAWAY", "count"=>"1341"},
{"date"=>"2020-09-19", "work_category"=>"RECEIVING", "count"=>"1052"},
{"date"=>"2020-09-20", "work_category"=>"CASE PICKS", "count"=>"5160"},
{"date"=>"2020-09-20", "work_category"=>"LOADING", "count"=>"2690"},
{"date"=>"2020-09-20", "work_category"=>"PALLET STAGING", "count"=>"2663"},
{"date"=>"2020-09-20", "work_category"=>"PUTAWAY", "count"=>"1554"},
{"date"=>"2020-09-20", "work_category"=>"RECEIVING", "count"=>"1536"},
{"date"=>"2020-09-21", "work_category"=>"CASE PICKS", "count"=>"2202"},
{"date"=>"2020-09-21", "work_category"=>"LOADING", "count"=>"860"},
{"date"=>"2020-09-21", "work_category"=>"PALLET STAGING", "count"=>"1004"},
{"date"=>"2020-09-21", "work_category"=>"PUTAWAY", "count"=>"1238"},
{"date"=>"2020-09-21", "work_category"=>"RECEIVING", "count"=>"954"}]
I need to pull out this dataset/hash/array from the above hash:
Logic:
Grab an array that lists the count keys values for each work_category row that matches the provided work_category key value of “CASE PICKS” for every date listed (maintaining the date order oldest -> newest).
Desired Result Set:
[ “21315”, “16842”, “24849”, “11806”, “8086”, “5160”, “2202” ]
Seems basic but I'm having some troubles... very green to Ruby. Anyone that could provide some help -- it would be greatly appreciated!

Answer 1

The following is a sub-array of the array given in the question.
arr = [
{"date"=>"2020-09-15", "work_category"=>"CASE PICKS", "count"=>"21315"},
{"date"=>"2020-09-15", "work_category"=>"LOADING", "count"=>"6401"},
{"date"=>"2020-09-15", "work_category"=>"PALLET STAGING", "count"=>"6649"},
{"date"=>"2020-09-15", "work_category"=>"PUTAWAY", "count"=>"4974"},
{"date"=>"2020-09-15", "work_category"=>"RECEIVING", "count"=>"4108"},
{"date"=>"2020-09-16", "work_category"=>"CASE PICKS", "count"=>"16842"},
{"date"=>"2020-09-16", "work_category"=>"LOADING", "count"=>"4987"},
{"date"=>"2020-09-16", "work_category"=>"PALLET STAGING", "count"=>"5716"},
{"date"=>"2020-09-16", "work_category"=>"PUTAWAY", "count"=>"6292"},
{"date"=>"2020-09-16", "work_category"=>"RECEIVING", "count"=>"4894"},
{"date"=>"2020-09-17", "work_category"=>"CASE PICKS", "count"=>"24849"},
{"date"=>"2020-09-17", "work_category"=>"LOADING", "count"=>"5303"}
]
It is only necessary to make a single pass through the array.
arr.each_with_object([]) do |h,arr|
arr << h["count"] if h["work_category"] == "CASE PICKS"
end
#=> ["21315", "16842", "24849"]

Answer 2

First, filter the items with select and then extract just the counts with map.
counts = arr
.select { |item| item["work_category"] == "CASE PICKS" }
.map { |item| item["count"] }