How do I sort an array of hashes by a value in the hash?

Question

This Ruby code is not behaving as I would expect:

# create an array of hashes
sort_me = []
sort_me.push({"value"=>1, "name"=>"a"})
sort_me.push({"value"=>3, "name"=>"c"})
sort_me.push({"value"=>2, "name"=>"b"})

# sort
sort_me.sort_by { |k| k["value"]}

# same order as above!
puts sort_me

I'm looking to sort the array of hashes by the key "value", but they are printed unsorted.

Answer 1

Ruby's sort doesn't sort in-place. (Do you have a Python background, perhaps?)

Ruby has sort! for in-place sorting, but there's no in-place variant for sort_by in Ruby 1.8. In practice, you can do:

sorted = sort_me.sort_by { |k| k["value"] }
puts sorted

As of Ruby 1.9+, .sort_by! is available for in-place sorting:

sort_me.sort_by! { |k| k["value"]}