Hash#deep_slice

hash_deep_slice.rb

class Hash

	def deep_slice(schema)
		self.class.deep_slice(self, schema)
	end

	def self.deep_slice(hash, schema)
	  nested_schemas = schema.last.is_a?(Hash) ? schema.last : {}
	  keys = schema.reject{|e| e.is_a?(Hash) } + nested_schemas.keys

	  hash.slice(*keys).map do |k,v|
		schema = nested_schemas[k]

		v = case
		when schema.nil?
		  v
		when v.is_a?(Hash)
		  deep_slice(v, schema)
		when v.is_a?(Array)
		  v.map{|e| deep_slice(e, schema.first) }
		when v.nil?
		  if schema.count == 1 && schema.first.is_a?(Array)
			[]
		  else
			{}
		  end
		end

		[k,v]
	  end.to_h
	end

end