Question

I am using Ruby on Rails 3.1 and I would like to order a Hash of Arrays by caring the order “stated”/”specified” in another Array. That is, for example, I have:

# This is the Hash of Arrays mentioned above.

hash = {
  1 => [
    "Value 1 1",
    "Value 1 2",
    "Value 1 n",
  ],
  2 => [
    "Value 2 1",
    "Value 2 2",
    "Value 2 n",
  ],
  3 => [
    "Value 3 1",
    "Value 3 2",
    "Value 3 n",
  ],
  m => [
    "Value m 1",
    "Value m 2",
    "Value m n",
  ]
}

and

# This is the Array mentioned above.

array = [m, 3, 1, 2]

I would like to order hash keys as “stated”/”specified” in the array in order to have:

# Note that Hash keys are ordered as in the Array.

ordered_hash = {
  m => [
    "Value m 1",
    "Value m 2",
    "Value m n",
  ],
  3 => [
    "Value 3 1",
    "Value 3 2",
    "Value 3 n",
  ],
  1 => [
    "Value 1 1",
    "Value 1 2",
    "Value 1 n",
  ],
  2 => [
    "Value 2 1",
    "Value 2 2",
    "Value 2 n",
  ]
}

How can I make that (maybe using the Enumerable Ruby module or some unknown to me Ruby on Rails method)?

Answer 1

sorted_array = hash.sort_by { |k,v| array.index(k) }

If you want ordering and a Hash, you’ll need to use ActiveSupport::OrderedHash, e.g.

sorted_array = hash.sort_by { |k,v| array.index(k) }
sorted_hash  = ActiveSupport::OrderedHash[sorted_array]