Map Enumerable to a Hash instead of an Array

map_hash.rb

module Enumerable
  def map_hash(memo = nil, &block)
    i = 0
    inject(memo || {}) do |hash, item|
      if kind_of?(Hash)
        key = item.first
        value = item.last
      else
        key = i
        value = item
      end
      mapped_value = yield(key, value)
      hash[mapped_value.first] = mapped_value.last
      i += 1
      hash
    end
  end
end

# With a Hash
res = {:foo => 1, :bar => 2}.map_hash do |key, value|
  [key, value * 10]
end
p res   # {:foo=>10, :bar=>20}

# With an Array:
res = [1, 2].map_hash do |index, value|
  [index, value * 10]
end
p res   # {0=>10, 1=>20}