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

My attempt, perhaps slightly more compact.

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

h.values.transpose.map { |s| Hash[h.keys.zip(s)] }

Should work in Ruby 1.9.3 or later.

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Explanation:

First, 'combine' the corresponding values into 'rows'

h.values.transpose
# => [["val1", "valb1"], ["val2", "valb2"]] 

Each iteration in the map block will produce one of these:

h.keys.zip(s)
# => [[:a, "val1"], [:b, "valb1"]]

and Hash[] will turn them into hashes:

Hash[h.keys.zip(s)]
# => {:a=>"val1", :b=>"valb1"}      (for each iteration)