Question

I have the following data structure in Ruby (a hash where keys are strings, and values are arrays).

X = { "id": [2, 4, 1],  "name": ["a", "b", "c"], "time": [1, 0, 2]}

I would like to sort the array associated with the field “time”, but I would like all other arrays to be sorted in a consistent manner. Example: after sorting, X should look like this.

X = {"id": [4, 2, 1], "name": ["b", "a", "c"], "time": [0, 1, 2]}

I solved this in a really ugly way (because I’m not sure how to do it). What I did was create a copy of time, then zip id and time, and sort it, then zip name and time_copy and sort it. Then unzip. I’m pretty sure this is an awful way to do it. Could someone else teach me a better method?

Answer 1

Using @tokland’s answer to another question and applying values_at to the result:

h = { id: [2, 4, 1],  name: ["a", "b", "c"], time: [1, 0, 2]}

time_indices = h[:time].each_with_index.sort_by(&:first).map(&:last)
h.values.each{|ar| ar.replace(ar.values_at(*time_indices))}
#=> {:id=>[4, 2, 1], :name=>["b", "a", "c"], :time=>[0, 1, 2]}