Turning a Hash of Arrays into an Array of Hashes in Ruby

Question

We have the following datastructures:

{:a => [\"val1\", \"val2\"], :b => [\"valb1\", \"valb2\"], ...}

And I want to turn that into

Answer 1

Using a functional approach (see Enumerable):

hs = h.values.transpose.map { |vs| h.keys.zip(vs).to_h }
#=> [{:a=>"val1", :b=>"valb1"}, {:a=>"val2", :b=>"valb2"}]

And back:

h_again = hs.first.keys.zip(hs.map(&:values).transpose).to_h
#=> {:a=>["val1", "val2"], :b=>["valb1", "valb2"]}