Hash#deep_slice

hash_deep_slice.rb

# Hash#deep_slice
#
# h = {
#   :a => 1, 
#   :b => 2, 
#   :c => {
#     :ca => 31, 
#     :cb => 32, 
#     :cc => 33
#   },
#   :d => {
#     :da => {
#       :daa => 411, 
#       :dab => 412
#     }, 
#     :db => {
#       :dba => 421
#     }
#   }, 
#   :e => nil
# }
# 
# 
# h.deep_slice(:a, :e)
#   {
#     :a => 1,
#     :e => nil
#   }
# 
# h.deep_slice(:a, :c => [:ca, :cc])
#   {
#     :a => 1,
#     :c => {
#       :ca => 31,
#       :cc => 33
#     }
#   }
# 
# h.deep_slice(:d => [{:da => :dab},  {:db => :dba}])
#   {
#     :d => {
#       :da => {
#         :dab => 412
#       }, 
#       :db => {
#         :dba => 421
#       }
#     }
#   }
# 
# h.deep_slice(:b=> :x,:e => :y)
#   {
#     :b => 2,
#     :e => nil
#   }
#
class Hash 
  def deep_slice(*keys)
    worker = ->(hash, key, acc) {
      return hash unless hash.is_a? Hash

      case key
        when Hash  then key.inject(acc){|h, (k, sk)| h.merge(k => worker.(hash[k], sk, {})) }
        when Array then key.inject(acc){|h, k| h.merge(worker.(hash, k, {})) }
        else acc.merge(hash.slice(key))
      end
    }
    
    worker.(self, keys, {})
  end
end